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2021-02-04 | Enhancing plasticity in high-entropy refractory ceramics via tailoring valence electron concentration | Bottom-up design of high-entropy ceramics is a promising approach for
realizing materials with unique combination of high hardness and
fracture-resistance at elevated temperature. This work offers a simple yet
fundamental design criterion - valence electron concentration (VEC) > ~9.5
e-/f.u. to populate bonding metallic states at the Fermi level - for selecting
elemental compositions that may form rocksalt-structure (B1) high-entropy
ceramics with enhanced plasticity (reduced brittleness). Single-phase B1
(HfTaTiWZr)C and (MoNbTaVW)C, chosen as representative systems due to their
specific VEC values, are here synthesized and tested. Nanoindentation arrays at
various loads and depths statistically show that (HfTaTiWZr)C (VEC=8.6 e-/f.u.)
is hard but brittle, whilst (MoNbTaVW)C (VEC=9.4 e-/f.u.) is hard and
considerably more resistant to fracture than (HfTaTiWZr)C. Ab initio molecular
dynamics simulations and electronic-structure analysis reveal that the improved
fracture-resistance of (MoNbTaVW)C subject to tensile and shear deformation may
originate from the intrinsic material's ability to undergo local lattice
transformations beyond tensile yield points, as well as from relatively facile
activation of lattice slip. Additional simulations, carried out to follow the
evolution in mechanical properties as a function of temperature, suggest that
(MoNbTaVW)C may retain good resistance to fracture up to ~900-1200K, whereas
(HfTaTiWZr)C is predicted to remain brittle at all investigated temperatures. | 2102.02455v2 |
2020-09-08 | High-Pressure Torsion Deformation Induced Phase Transformations and Formations: New Material Combinations and Advanced Properties | Heavy plastic shear deformation at relatively low homologous temperatures is
called high-pressure torsion (HPT) deformation, which is one method of severe
plastic deformation (SPD). The aim of the paper is to give an overview of a new
processing approach which permits the generation of innovative metastable
materials and novel nanocomposites by HPT deformation. Starting materials can
be either coarse-grained multi-phase alloys, a mixture of different elemental
powders or any other combination of multiphase solid starting materials. After
HPT processing, the achievable microstructures are similar to the ones
generated by mechanical alloying. Nevertheless, one advantage of the HPT
process is that bulk samples of the different types of metastable materials and
nanocomposites are obtained directly during HPT deformation. It will be shown
that different material combinations can be selected and materials with
tailored properties, or in other words, materials designed for specific
applications and the thus required properties, can be synthesized. Areas of
application for these new materials range from hydrogen storage to materials
resistant to harsh radiation environments. | 2009.03531v1 |
2023-12-08 | Low Resistance Ohmic Contact to P-type Monolayer WSe2 | Advanced microelectronics in the future may require semiconducting channel
materials beyond silicon. Two-dimensional (2D) semiconductors, characterized by
their atomically thin thickness, hold immense promise for high-performance
electronic devices at the nanometer scale with lower heat dissipation. One
challenge for achieving high-performance 2D semiconductor field effect
transistors (FET), especially for p-type materials, is the high electrical
contact resistance present at the metal-semiconductor interface. In
conventional bulk semiconductors, low resistance ohmic contact is realized
through heavy substitutional doping with acceptor or donor impurities at the
contact region. The strategy of substitutional doping, however, does not work
for p-type 2D semiconductors such as monolayer tungsten diselenide (WSe$_2$).In
this study, we developed highly efficient charge-transfer doping with
WSe$_2$/$\alpha$-RuCl$_3$ heterostructures to achieve low-resistance ohmic
contact for p-type WSe$_2$ transistors. We show that a hole doping as high as
3$\times$10$^{13}$ cm$^{-2}$ can be achieved in the WSe$_2/\alpha$-RuCl$_3$
heterostructure due to its type-III band alignment. It results in an Ohmic
contact with resistance lower than 4 k Ohm $\mu$m at the p-type monolayer
WSe$_2$/metal junction. at room temperature. Using this low-resistance contact,
we demonstrate high-performance p-type WSe$_2$ transistors with a saturation
current of 35 $\mu$A$\cdot$ $\mu$m$^{-1}$ and an I$_{ON}$/I$_{OFF}$ ratio
exceeding 10$^9$ It could enable future microelectronic devices based on 2D
semiconductors and contribute to the extension of Moore's law. | 2312.04849v1 |
2022-01-06 | Model-based quantitative methods to predict irradiation-induced swelling in alloys | Predicting volume swelling of structural materials in nuclear reactors under
high-dose neutron irradiations based on existing low-dose experiments or
irradiation data with high-dose-rate energetic particles has been a
long-standing challenge for safety evaluation and rapidly screening
irradiation-resistant materials in nuclear energy systems. Here, we build an
Additional Defect Absorption Model that describes the irradiation-induced
swelling effects produced by energetic electrons, heavy-ions, and neutrons by
considering additional defect sinks inherent in the irradiation process. Based
on this model, we establish quantitative methods to predict high-dose swelling
from low-dose behavior and obtain the equivalent irradiation dose for different
energetic particles when the dose rates differ by several orders of magnitude.
Furthermore, we propose a universal parameter to characterize the swelling
resistance of various alloys and predict their radiation tolerances under
different radiation conditions. This work provides quantitative prediction
methods for evaluating irradiation-induced swelling effects of structural
materials, which is critical to the safety and material development for
advanced nuclear reactors. | 2201.04958v1 |
2022-10-28 | An innovative materials design protocol for the development of novel refractory high-entropy alloys for extreme environments | In the quest of new materials that can withstand severe irradiation and
mechanical extremes for advanced applications (e.g. fission reactors, fusion
devices, space applications, etc), design, prediction and control of advanced
materials beyond current material designs become a paramount goal. Here, though
a combined experimental and simulation methodology, the design of a new
nanocrystalline refractory high entropy alloy (RHEA) system is established.
Compositions of this alloy, assessed under extreme environments and in situ
electron-microscopy, revealed both high mechanical strength and thermal
stability, grain refinement under heavy ion irradiation and outstanding
irradiation resistance to dual-beam irradiation and helium implantation, marked
by remarkable resistance to defect generation, growth and coalescence. The
experimental and modeling results, which demonstrated notable agreement, can be
applied to design and rapidly assess other alloys subjected to extreme
environmental conditions. | 2210.16409v1 |
2023-02-07 | Effect of ZrB$_2$ additions on the thermal stability of polycrystalline diamond | This study investigates the effect of ZrB$_2$ additions on the
microstructure, thermal stability, and thermo-mechanical wear behaviour of
polycrystalline diamond. Following high-pressure high-temperature (HPHT)
sintering, the ZrB$_2$-PCD material showed a full conversion of the binder
phase to cobalt-boride (Co2B and Co$_{23}$B$_6$) phases. In-situ PXRD and TEM
vacuum annealing experiments observed that the onset of bulk graphitisation
occurred above $1000^{\circ}C$ for the ZrB$_2$-PCD material, compared to
$850^{\circ}C$ for the STD-PCD material. The ZrB$_2$-PCD tools showed excellent
thermo-mechanical wear behaviour, exhibiting increased durability and a steady
wear scar progression during high-temperature dry-VTL testing. However, lowered
abrasion wear resistance was observed for the ZrB2-PCD tools during
low-temperature wet-VTL testing, probably due the reduced diamond contiguity in
the ZrB2 additive sample. Further optimisation of the ZrB$_2$ additive phase
content, mixing methodology, or sintering conditions could be explored to
improve the abrasive wear resistance of this novel PCD material. | 2302.03464v1 |
2016-06-14 | Origin of the metal-to-insulator crossover in cuprate superconductors | Superconductivity in cuprates peaks in the doping regime between a metal at
high p and an insulator at low p. Understanding how the material evolves from
metal to insulator is a fundamental and open question. Early studies in high
magnetic fields revealed that below some critical doping an insulator-like
upturn appears in the resistivity of cuprates at low temperature, but its
origin has remained a puzzle. Here we propose that this 'metal-to-insulator
crossover' is due to a drop in carrier density n associated with the onset of
the pseudogap phase at a critical doping p*. We use high-field resistivity
measurements on LSCO to show that the upturns are quantitatively consistent
with a drop from n=1+p above p* to n=p below p*, in agreement with high-field
Hall data in YBCO. We demonstrate how previously reported upturns in the
resistivity of LSCO, YBCO and Nd-LSCO are explained by the same universal
mechanism: a drop in carrier density by 1.0 hole per Cu atom. | 1606.04491v1 |
2020-05-30 | Linearity and rate capability measurements of RPC with semi-insulating crystalline electrodes operating in avalanche mode | The intrinsic rate capability and the ageing properties of the Resistive
Plate Chambers are closely related to the electrodes material and to the
front-end electronics threshold. The development of a low noise pre-amplifier
led us to improve the intrinsic rate capability of High Pressure Laminate
(bakelite) up to $\sim10\;kHz/cm^2$, nevertheless the effective rate is
significantly limited by electrodes ageing. To further improve the effective
rate capability new materials are investigated. A Resistive Plate Chamber with
crystalline semi-insulating Gallium Arsenide electrodes has been characterized
with high energy electrons beam at the Beam Test Facility (BFT), (INFN National
Laboratory of Frascati, Italy). The response of the Resistive Plate Chamber to
multiple bunched electrons was measured operating the detector in avalanche
mode. The intrinsic rate capability has been also measured operating the
detector in a uniform high energy gamma radiation field at the GIF++ facility
(EHN1 of SPS, CERN). | 2006.00306v1 |
2016-06-17 | Manganite-based three level memristive devices with self-healing capability | We report on non-volatile memory devices based on multifunctional manganites.
The electric field induced resistive switching of
Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/n-Si devices is explored using different
measurement protocols. We show that using current as the electrical stimulus
(instead of standard voltage-controlled protocols) improves the electrical
performance of our devices and unveils an intermediate resistance state. We
observe three discrete resistance levels (low, intermediate and high), which
can be set either by the application of current-voltage ramps or by means of
single pulses. These states exhibit retention and endurance capabilities
exceeding $10^4$ s and 70 cycles, respectively. We rationalize our experimental
observations by proposing a mixed scenario were a metallic filament and a
Si$O_x$ layer coexist, accounting for the observed resistive switching. Overall
electrode area dependence and temperature dependent resistance measurements
support our scenario. After device failure takes place, the system can be
turned functional again by heating up to low temperature (120 C), a feature
that could be exploited for the design of memristive devices with self-healing
functionality. These results give insight into the existence of multiple
resistive switching mechanisms in manganite-based memristive systems and
provide strategies for controlling them. | 1606.05401v1 |
2019-07-25 | Extraction of the short-range defect potential parameters from available experimental data on the graphene resistance | We consider a problem of obtaining information about the scattering
potentials of the monolayer graphene sample using available experimental data
on its resistance. We have in mind a development of the study describing
super-high mobility electrons in suspended samples without chemical doping. As
far as practical absence of the doping impurities in this case makes the
Coulomb scattering negligible, we consider models of the short-range scattering
potentials. The model of short-range potential is assumed to be supported by
the close vicinity of the ring or the circumference of a circle. The diameter
of circles is supposed to be of the order of the crystal lattice spacing. The
empty core of the model potential guarantees the suppression of nonphysical
shortwave modes. Two models are investigated: the delta function on the
circumference of a circle (delta shell) and the annual well. An advantage of
the former is simplicity, while a virtue of the latter is regularity. We
consider scattering of electrons by these potentials and obtain exact explicit
formulae for the scattering data. We here discuss application of these formulae
for calculation of observables. Namely, we analyze the contribution of this
scattering into the graphene resistance and plot the resistivity as a function
of the Fermi energy according to our theoretical formulae. The obtained results
are consistent with experiment, where the resistance was measured as a function
of the Fermi momentum on the suspended annealed graphene. This fact gives a
possibility to find parameters of the modeled potential on the base of the
available experimental data on resistance of the suspended graphene sample with
the gate voltage controlled Fermi level position. It is clear to be very
important for applications. | 1907.10894v1 |
2021-08-23 | Polarization and resistive switching in epitaxial 2 nm Hf$_{0.5}$Zr$_{0.5}$O$_2$ tunnel junctions | In the quest for reliable and power-efficient memristive devices,
ferroelectric tunnel junctions are being investigated as potential candidates.
CMOS-compatible ferroelectric hafnium oxides are at the forefront. However, in
epitaxial tunnel devices with thicknesses around ${\approx}$ 4 - 6 nm, the
relatively high tunnel energy barrier produces a large resistance that
challenges their implementation. Here, we show that ferroelectric and
electroresistive switching can be observed in ultrathin 2 nm epitaxial
Hf$_{0.5}$Zr$_{0.5}$O$_2$ (HZO) tunnel junctions in large area capacitors
(${\approx} 300{\mu}m^2$). We observe that the resistance area product is
reduced to about 160 ${\Omega}{\cdot}$cm$^2$ and 65 ${\Omega}{\cdot}$cm$^2$ for
OFF and ON resistance states, respectively. These values are two orders of
magnitude smaller than those obtained in equivalent 5 nm HZO tunnel devices
while preserving a similar OFF/ON resistance ratio (210 ${\%}$). The devices
show memristive and spike-timing-dependent plasticity (STDP) behavior and good
retention. Electroresistance and ferroelectric loops closely coincide,
signaling ferroelectric switching as a driving mechanism for resistance change. | 2108.10373v1 |
2002-08-18 | Synthesis and physical properties of LiBC intermetallics | Polycrystalline samples of LiBC compounds, which were predicted as possible
candidate for high-Tc superconductivity, have been synthesised by a flux method
and investigated by means of electrical resistivity and magnetic
susceptibility. Scanning electron microscopy and X-ray diffraction patterns
showed a plate-like morphology and a single-phase nature of LiBC samples for
starting composition of Li1.25BC (flux composition). The lattice constants a, c
display a systematic variation with x and has maximum volume of the hexagonal
unit cell at x = 1.25. Electrical resistivity measurements revealed an
extrinsic semi-conducting behaviour of the single-phase LiBC with an activation
energy of 18 meV and a maximum specific resistivity of 2.5 Wcm at 300 K. In
contrast to the theoretical prediction of high Tc, no superconducting features
were detected down to 2 K both, by measurements of electrical resistivity and
magnetic susceptibility. | 0208346v2 |
2008-10-22 | Quantum resistance metrology in graphene | We have performed a metrological characterization of the quantum Hall
resistance in a 1 $\mu$m wide graphene Hall-bar. The longitudinal resistivity
in the center of the $\nu=\pm 2$ quantum Hall plateaus vanishes within the
measurement noise of 20 m$\Omega$ upto 2 $\mu$A. Our results show that the
quantization of these plateaus is within the experimental uncertainty (15 ppm
for 1.5$ \mu$A current) equal to that in conventional semiconductors. The
principal limitation of the present experiments are the relatively high contact
resistances in the quantum Hall regime, leading to a significantly increased
noise across the voltage contacts and a heating of the sample when a high
current is applied. | 0810.4064v1 |
2011-02-14 | Coexistence of superconductivity and antiferromagnetism in single crystals $A_{0.8}Fe_{2-y}Se_2$ (A= K, Rb, Cs, Tl/K and Tl/Rb): evidence from magnetization and resistivity | We measure the resistivity and magnetic susceptibility in the temperature
range from 5 K to 600 K for the single crystals $A$Fe$_{2-y}$Se$_2$ ($A$ =
K$_{0.8}$, Rb$_{0.8}$, Cs$_{0.8}$, Tl$_{0.5}$K$_{0.3}$ and
Tl$_{0.4}$Rb$_{0.4}$). A sharp superconducting transition is observed in low
temperature resistivity and susceptibility, and susceptibility shows 100%
Meissner volume fraction for all crystals, while an antiferromagnetic
transition is observed in susceptibility at Neel temperature ($T_N$) as high as
500 K to 540 K depending on A. It indicates the coexistence of
superconductivity and antiferromagnetism. A sharp increase in resistivity
arises from the structural transition due to Fe vacancy ordering at the
temperature slightly higher than $T_{\rm N}$. Occurrence of superconductivity
in an antiferromagnetic ordered state with so high $T_{\rm N}$ may suggest new
physics in this type of unconventional superconductors. | 1102.2783v1 |
2012-08-15 | Two-dimensional electron-gas-like charge transport at magnetic Heusler alloy-SrTiO$_3$ interface | We report remarkably low residual resistivity, giant residual resistivity
ratio, free-electron-like Hall resistivity and high mobility ($\approx$ 10$^4$
cm$^2$V$^{-1}$s$^{-1}$) charge transport in epitaxial films of Co$_2$MnSi and
Co$_2$FeSi grown on (001) SrTiO$_3$. This unusual behavior is not observed in
films deposited on other cubic oxide substrates of comparable lattice
parameters. The scaling of the resistivity with thickness of the films allow
extraction of interface conductance, which can be attributed to a layer of
oxygen vacancies confined within 1.9 nm of the interface as revealed by
atomically resolved electron microscopy and spectroscopy. The high mobility
transport observed here at the interface of a fully spin polarized metal is
potentially important for spintronics applications. | 1208.3099v2 |
2014-10-29 | Large time-dependent coercivity and resistivity modification under sustained voltage application in a Pt/Co/AlOx/Pt junction | The coercivity and resistivity of a Pt/Co/AlOx/Pt junction are measured under
sustained voltage application. High bias voltages of either polarity are
determined to cause a strongly enhanced, reversible coercivity modification
compared to low voltages. Time-resolved measurements show a logarithmic
development of the coercive field in this regime, which continues over a period
as long as thirty minutes. Furthermore, the resistance of the dielectric
barrier is found to change strongly and reversibly on the same time scale,
suggesting an electrochemical process is taking place within the dielectric. It
is argued that the migration of oxygen vacancies at the magnet/oxide interface
could explain both the resistance variation and the enhanced electric field
effect at high voltages. A thermal fluctuation aftereffect model is applied to
account for the observed logarithmic dependence. | 1410.8018v1 |
2017-06-29 | Effect of Anodizing Parameters on Corrosion Resistance of Coated Purified Magnesium | Magnesium and its alloys are being considered for biodegradable biomaterials.
However, high and uncontrollable corrosion rates have limited the use of
magnesium and its alloys in biological environments. In this research, high
purified magnesium (HP-Mg) was coated with stearic acid in order to improve the
corrosion resistance of magnesium. Anodization and immersion in stearic acid
were used to form a hydrophobic layer on magnesium substrate. Different DC
voltages, times, electrolytes, and temperatures were tested. Electrochemical
impedance spectroscopy and potentiodynamic polarization were used to measure
the corrosion rates of the coated HP-Mg. The results showed that optimum
corrosion resistance occurred for specimens anodized at +4 volts for 4 minutes
at 70{\deg}C in borate benzoate. The corrosion resistance was temporarily
enhanced by 1000x. | 1706.09547v1 |
2017-12-08 | Selective etching of PDMS: etching as a negative tone resist | In this work authors present for the first time how to apply the
additive-free, cured PDMS as a negative tone resist material, demonstrate the
creation of PDMS microstructures and test the solvent resistivity of the
created microstructures. The PDMS layers were 45 um and 100 um thick, the
irradiations were done with a focused proton microbeam with various fluences.
After irradiation, the samples were etched with sulfuric acid that removed the
unirradiated PDMS completely but left those structures intact that received
high enough fluences. The etching rate of the unirradiated PDMS was also
determined. Those structures that received at least 7.5*10^15 ion*cm-2 fluence
did not show any signs of degradation even after 19 hours of etching. As a
demonstration, 45 um and 100 um tall, high aspect ratio, good quality,
undistorted microstructures were created with smooth and vertical sidewalls.
The created microstructures were immersed into numerous solvents and some acids
to test their compatibility. It was found that the unirradiated PDMS cannot,
while the irradiated PDMS microstructures can resist to chloroform, n-hexane,
toluene and sulfuric acid. Hydrogen fluoride etches both the unirradiated and
the irradiated PDMS. | 1712.03119v1 |
2018-06-28 | Band-edge quasiparticles from electron phonon coupling and resistivity saturation | We address the problem of resistivity saturation observed in materials such
as the A-15 compounds. To do so, we calculate the resistivity for the
Hubbard-Holstein model in infinite spatial dimensions to second order in
on-site repulsion $U\leq D$ and to first order in (dimensionless)
electron-phonon coupling strength $\lambda\leq0.5$, where $D$ is the
half-bandwidth. We identify a unique mechanism to obtain two parallel quantum
conducting channels: low-energy and band-edge high-energy quasi-particles. We
identify the source of the hitherto unremarked high-energy quasi-particles as a
positive slope in the frequency-dependence of the real part of the electron
self-energy. In the presence of phonons, the self-energy grows linearly with
the temperature at high-$T$, causing the resistivity to saturate. As $U$ is
increased, the saturation temperature is pushed to higher values, offering a
mechanism by which electron-correlations destroy saturation. | 1806.11227v2 |
2019-06-15 | Unidirectional Synapse-Like Behavior of Zr/ZrO2-NT/Au Layered Structure | Zirconia nanotubular layer with an outer tube diameter 25 nm was synthesized
by potentiostatic anodization. The Zr/ZrO2-NT/Au memristive structure is
fabricated using stencil mask and magnetron sputtering techniques.
Current-voltage characteristics are measured in full cycles of resistive
switching with varying parameters of the applied harmonic voltage. An
equivalent circuit with unidirectional electrical conductivity for the studied
structure is proposed. Estimates of the electrical resistance of memristors in
high-and intermediate resistivity states are performed. The high synaptic
plasticity of memristors based on the Zr/ZrO2-NT/Au structure is shown. | 1906.06549v1 |
2019-06-25 | Compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors | In this letter, we design and demonstrate an improved MOCVD grown reverse
Al-composition graded contact layer to achieve low resistance contact to MOCVD
grown ultra-wide bandgap (UWBG) Al0.70Ga0.30N channel metal semiconductor
field-effect transistors (MESFETs). Increasing the thickness of the reverse
graded layer was found to improve contact layer resistance significantly,
leading to contact resistance of 3.3x10^-5 Ohm.cm2. Devices with gate length,
LG, of 0.6 microns and source-drain spacing, LSD, of 1.5 microns displayed a
maximum current density, IDSMAX, of 635 mA/mm with an applied gate voltage,
VGS, of +2 V. Breakdown measurements on transistors with gate to drain spacing,
LGD, of 770 nm had breakdown voltage greater than 220 , corresponding to
minimum breakdown field of 2.86 MV/cm. This work provides a framework for the
design of low resistance contacts to MOCVD grown high Al-content AlxGa1-xN
channel transistors. | 1906.10270v2 |
2021-02-05 | Formation of Ultra-High-Resistance Au/Ti/p-GaN Junctions and the Applications in AlGaN/GaN HEMTs | We report a dramatic current reduction, or a resistance increase, by a few
orders of magnitude of two common-anode Au/Ti/pGaN Schottky junctions annealed
within a certain annealing condition window (600 - 700 oC, 1 - 4 min). Results
from similar common-anode Schottky junctions made of Au/p-GaN, Al/Ti/p-GaN and
Au/Ti/graphene/p-GaN junctions demonstrated that all the three layers (Au, Ti
and p-GaN) are essential for the increased resistance. Raman characterization
of the p-GaN showed a decrease of the Mg-N bonding, i.e., the deactivation of
Mg, which is consistent with the Hall measurement results. Moreover, this
high-resistance junction structure was employed in p-GaN gate AlGaN/GaN HEMTs.
It was shown to be an effective gate technology that was capable to boost the
gate breakdown voltage from 9.9 V to 13.8 V with a negligible effect on the
threshold voltage or the sub-threshold slope. | 2102.03418v1 |
2021-12-02 | Homes' law in holographic superconductor with linear-$T$ resistivity | Homes' law, $\rho_{s} = C \, \sigma_{DC} \, T_{c}$, is a universal relation
of superconductors between the superfluid density $\rho_{s}$ at zero
temperature, the critical temperature $T_{c}$ and the electric DC conductivity
$\sigma_{DC}$ at $T_c$. Experimentally, Homes' law is observed in high $T_c$
superconductors with linear-$T$ resistivity in the normal phase, giving a
material independent universal constant $C$. By using holographic models
related to the Gubser-Rocha model, we investigate how Homes' law can be
realized together with linear-$T$ resistivity in the presence of momentum
relaxation. We find that strong momentum relaxation plays an important role to
exhibit Homes' law with linear-$T$ resistivity. | 2112.01153v2 |
2004-02-02 | Universal charge transport of the Mn oxides in the high temperature limit | We have found that various Mn oxides have the universal resistivity and
thermopower in the high temperature limit. The resistivities and thermopowers
of all the samples go toward constant values of 7$\pm$1 m$\Omega$cm and
$-79\pm$3 $\mu$V/K, which are independent of carrier density and crystal
structures. We propose that the electric conduction occurs in a highly
localized way in the high temperature limit, where the exchange of entropy and
charge occurs in the neighboring Mn$^{3+}$ and Mn$^{4+}$ ions. | 0402032v1 |
2009-05-19 | Boosting electronic transport in carbon nanotubes by isotopic disorder | The current/voltage curve of metallic carbon nanotubes (CNTs) displays at
high bias a sudden increase of the resistivity due to the scattering of
electrons with phonons having an anomalously-high population (hot phonons).
Here, we show that it is possible to improve the electrical performances of
metallic CNTs by C13 isotope enrichment. In fact, isotopic disorder creates
additional channels for the hot-phonon deexcitation, reduces their population
and, thus, the nanotube high-bias differential-resistance. This is an
extraordinary case where disorder improves the electronic transport. | 0905.3034v1 |
2011-04-05 | Effect of uniaxial stress on low-frequency dispersion of dielectric constant in high-resistivity GaSe crystals | Low-frequency dielectric spectra of high-resistivity GaSe layered crystals
have been studied on the samples clamped between two insulating parallel plates
at frequencies up to 100 kHz. The measurements have been carried out at
different uniaxial stresses up to $2.4\times10^5$ Pa applied along the c-axis
normal to crystal layer's plane. It is revealed that the dielectric spectra of
high-resistivity GaSe layered crystals with insulating plates obey a universal
power law ${\sim}\omega^{n-1}$, where ${\omega}$ is the angular frequency and
$n\approx 0.8$, earlier observed on high-resistivity GaSe crystals with
indium-soldered contacts. The same type of spectra on the crystals with
different types of contacts (insulating and ohmic) confirms the bulk character
of the observed polarization caused by hopping charge carriers. It is shown
that the frequency-dependent dielectric constant increases linearly with the
uniaxial stress characterized by the coefficient
${\Delta}{\epsilon}/({\epsilon}{\Delta}{p})=8{\times}10^{-7}$ Pa$^{-1}$. A
slight increase of power $1-n$ with the stress is observed, that leads to a
stronger dielectric dispersion. The strong stress dependence of the
low-frequency dielectric constant in high-resistivity GaSe crystals may be
referred to the presence of the formations of elementary dipoles, rotations of
which correspond to hops of localized charge carriers. | 1104.0801v1 |
2017-12-08 | Selective etching of PDMS: etching as positive resist | Although, poly(dimethylsiloxane) (PDMS) is a widely used material in numerous
applications, such as micro- or nanofabrication, the method of its selective
etching has not been known up to now. In this work authors present two methods
of etching the pure, additive-free and cured PDMS as a positive resist
material.
To achieve the chemical modification of the polymer necessary for selective
etching, energetic ions were used. We created 7 um and 45 um thick PDMS layers
and patterned them by a focused proton microbeam with various, relatively large
fluences. In this paper authors demonstrate that 30 wt% Potassium Hydroxide
(KOH) or 30 wt% sodium hydroxide (NaOH) at 70 oC temperature etch proton
irradiated PDMS selectively, and remove the chemically sufficiently modified
areas. In case of KOH development, the maximum etching rate was approximately
3.5 um/minute and it occurs at about 7.5*10^15 ion*cm-2. In case of NaOH
etching the maximum etching rate is slightly lower, 1.75 um/minute and can be
found at the slightly higher fluence of 8.75*10^15 ion*cm-2.
These results are of high importance since up to this time it has not been
known how to develop the additive-free, cross-linked poly(dimethylsiloxane) in
lithography as a positive tone resist material. | 1712.03125v1 |
2021-04-14 | Inverse design of glass structure with deep graph neural networks | Directly manipulating the atomic structure to achieve a specific property is
a long pursuit in the field of materials. However, hindered by the disordered,
non-prototypical glass structure and the complex interplay between structure
and property, such inverse design is dauntingly hard for glasses. Here,
combining two cutting-edge techniques, graph neural networks and swap Monte
Carlo, we develop a data-driven, property-oriented inverse design route that
managed to improve the plastic resistance of Cu-Zr metallic glasses in a
controllable way. Swap Monte Carlo, as "sampler", effectively explores the
glass landscape, and graph neural networks, with high regression accuracy in
predicting the plastic resistance, serves as "decider" to guide the search in
configuration space. Via an unconventional strengthening mechanism, a
geometrically ultra-stable yet energetically meta-stable state is unraveled,
contrary to the common belief that the higher the energy, the lower the plastic
resistance. This demonstrates a vast configuration space that can be easily
overlooked by conventional atomistic simulations. The data-driven techniques,
structural search methods and optimization algorithms consolidate to form a
toolbox, paving a new way to the design of glassy materials. | 2104.06632v3 |
2021-05-07 | Integrating superconducting van der Waals materials on paper substrates | Paper has the potential to dramatically reduce the cost of electronic
components. In fact, paper is 10 000 times cheaper than crystalline silicon,
motivating the research to integrate electronic materials on paper substrates.
Among the different electronic materials, van der Waals materials are
attracting the interest of the scientific community working on paper-based
electronics because of the combination of high electrical performance and
mechanical flexibility. Up to now, different methods have been developed to
pattern conducting, semiconducting and insulating van der Waals materials on
paper but the integration of superconductors remains elusive. Here, the
deposition of NbSe2, an illustrative van der Waals superconductor, on standard
copy paper is demonstrated. The deposited NbSe2 films on paper display
superconducting properties (e.g. observation of Meissner effect and resistance
drop to zero-resistance state when cooled down below its critical temperature)
similar to those of bulk NbSe2. | 2105.03487v1 |
2016-01-17 | Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2 | In topological insulators (TIs), metallic surface conductance saturates the
insulating bulk resistance with de- creasing temperature, resulting in
resistivity plateau at low temperatures as a transport signature originating
from metallic surface modes protected by time reversal symmetry (TRS). Such
characteristic has been found in several materials including Bi2Te2Se, SmB6
etc. Recently, similar behavior has been observed in metallic com- pound LaSb,
accompanying an extremely large magetoresistance (XMR). Shubnikov-de Hass (SdH)
oscillation at low temperatures further confirms the metallic behavior of
plateau region under magnetic fields. LaSb[1] has been proposed by the authors
as a possible topological semimetal (TSM), while negative magnetoresistance is
absent at this moment. Here, high quality single crystals of NbAs2/TaAs2 with
inversion symmetry have been grown and the resistivity under magnetic field is
systematically investigated. Both of them exhibit metallic behavior under zero
magnetic field, and a metal-to-insulator transition occurs when a nonzero
magnetic field is applied, resulting in XMR (1.0*105% for NbAs2 and 7.3*105%
for TaAs2 at 2.5 K & 14 T). With tempera- ture decreased, a resistivity plateau
emerges after the insulator-like regime and SdH oscillation has also been
observed in NbAs2 and TaAs2. | 1601.04239v1 |
2018-09-26 | Changes in the near edge X-ray absorption fine structure of hybrid organic-inorganic resists upon exposure | We report on the near edge X-ray absorption fine structure (NEXAFS)
spectroscopy of hybrid organic-inorganic resists. These materials are
nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized
from organically modified precursors and transition metal alkoxides by a
sol-gel route and designed for ultraviolet, extreme ultraviolet and electron
beam lithography. The experiments were conducted using a scanning transmission
X-ray microscope (STXM) which combines high spatial-resolution microscopy and
NEXAFS spectroscopy. The absorption spectra were collected in the proximity of
the carbon edge (~ 290 eV) before and after in situ exposure, enabling the
measurement of a significant photo-induced degradation of the organic group
(phenyl or methyl methacrylate, respectively), the degree of which depends on
the configuration of the ligand. Photo-induced degradation was more efficient
in the resist synthesized with pendant phenyl substituents than it was in the
case of systems based on bridging phenyl groups. The degradation of the methyl
methacrylate group was relatively efficient, with about half of the initial
ligands dissociated upon exposure. Our data reveal that the such dissociation
can produce different outcomes, depending on the structural configuration.
While all the organic groups were expected to detach and desorb from the resist
in their entirety, a sizeable amount of them remain and form undesired
byproducts such as alkene chains. In the framework of the materials synthesis
and engineering through specific building blocks, these results provide a
deeper insight into the photochemistry of resists, in particular for extreme
ultraviolet lithography. | 1809.09916v1 |
2022-04-30 | A simple strategy to measure the contact resistance between metals and doped organic films | Charge injection from electrodes into doped organic films is a widespread
technology used in the majority of state-of-the-art organic semiconductor
devices. Although such interfaces are commonly considered to form Ohmic
contacts via strong band bending, an experiment that directly measures the
contact resistance has not yet been demonstrated. In this study, we use a
simple metal/doped organic semiconductor/metal stack and study its
voltage-dependent resistance. A transport layer thickness variation proves that
the presented experiment gains direct access to the contact resistance of the
device. We can quantify that for an operating current density of 10mA/cm2 the
investigated material system exhibits a voltage drop over the metal/organic
interface of about 200mV, which can be reduced by more than one order of
magnitude when employing an additional injection layer. The presented
experiment proposes a simple strategy to measure the contact resistance between
any metal and doped organic film without applying numerical tools or elaborate
techniques. Furthermore, the simplistic device architecture allows for very
high, homogeneous, and tunable electric fields within the organic layer, which
enables a clear investigation of the Poole-Frenkel effect. | 2205.00261v1 |
2018-01-30 | Novel circuit design for high-impedance and non-local electrical measurements of two-dimensional materials | Two-dimensional materials offer a novel platform for the development of
future quantum technologies. However, the electrical characterisation of
topological insulating states, non-local resistance and bandgap tuning in
atomically-thin materials, can be strongly affected by spurious signals arising
from the measuring electronics. Common-mode voltages, dielectric leakage in the
coaxial cables and the limited input impedance of alternate-current amplifiers
can mask the true nature of such high-impedance states. Here, we present an
optical isolator circuit which grants access to such states by electrically
decoupling the current-injection from the voltage-sensing circuitry. We
benchmark our apparatus against two state-of-the-art measurements: the
non-local resistance of a graphene Hall bar and the transfer characteristic of
a WS2 field-effect transistor. Our system allows the quick characterisation of
novel insulating states in two-dimensional materials with potential
applications in future quantum technologies. | 1801.10135v1 |
2013-08-31 | Origin of defects responsible for charge transport in resistive random access memory based on hafnia | A promising candidate for universal memory, which would involve combining the
most favourable properties of both high-speed dynamic random access memory
(DRAM) and non-volatile flash memory, is resistive random access memory
(ReRAM). ReRAM is based on switching back and forth from a high-resistance
state (HRS) to a low-resistance state (LRS). ReRAM cells are small, allowing
for the creation of memory on the scale of terabits. One of the most promising
materials for use as the active medium in resistive memory is hafnia (HfO$_2$).
However, an unresolved physics is the nature of defects and traps that are
responsible for the charge transport in HRS state of resistive memory.
In this study, we demonstrated experimentally and theoretically that oxygen
vacancies are responsible for the HRS charge transport in resistive memory
elements based on HfO$_2$. We also demonstrated that LRS transport occurs
through a mechanism described according to percolation theory.
Based on the model of multiphonon tunneling between traps, and assuming that
the electron traps are oxygen vacancies, good quantitative agreement between
the experimental and theoretical data of current-voltage characteristics were
achieved. The thermal excitation energy of the traps in hafnia was determined
based on the excitation spectrum and luminescence of the oxygen vacancies.
The findings of this study demonstrate that in resistive memory elements
using hafnia, the oxygen vacancies in hafnia play a key role in creating
defects in HRS charge transport. | 1309.0071v2 |
2020-09-26 | Optical imaging of strain-mediated phase coexistence during electrothermal switching in a Mott insulator | Resistive-switching -- the current-/voltage-induced electrical resistance
change -- is at the core of memristive devices, which play an essential role in
the emerging field of neuromorphic computing. This study is about resistive
switching in a Mott-insulator, which undergoes a thermally driven
metal-to-insulator transition. Two distinct switching mechanisms were reported
for such a system: electric-field-driven resistive switching and electrothermal
resistive switching. The latter results from an instability caused by Joule
heating. Here, we present the visualization of the reversible resistive
switching in a planar V$_2$O$_3$ thin-film device using high-resolution
wide-field microscopy in combination with electric transport measurements. We
investigate the interaction of the electrothermal instability with the
strain-induced spontaneous phase-separation in the V$_2$O$_3$ thin film at the
Mott-transition. The photomicrographs show the formation of a narrow metallic
filament with a minimum width $\lesssim$ 500\,nm. Although the filament
formation and the overall shape of the current-voltage characteristics (IVCs)
are typical of an electrothermal breakdown, we also observe atypical effects
like oblique filaments, filament splitting, and hysteretic IVCs with
sawtooth-like jumps at high currents in the low-resistance regime. We were able
to reproduce the experimental results in a numerical model based on a
two-dimensional resistor network. This model demonstrates that resistive
switching, in this case, is indeed electrothermal and that the intrinsic
heterogeneity is responsible for the atypical effects. This heterogeneity is
strongly influenced by strain, thereby establishing a link between switching
dynamics and structural properties. | 2009.12536v2 |
2023-10-01 | Elucidating Dynamic Conductive State Changes in Amorphous Lithium Lanthanum Titanate for Resistive Switching Devices | Exploration of novel resistive switching materials attracts attention to
replace conventional Si-based transistors and to achieve neuromorphic computing
that can surpass the limit of the current Von-Neumann computing for the time of
Internet of Things (IoT). Materials priorly used to serve in batteries have
demonstrated metal-insulator transitions upon an electrical biasing due to
resulting compositional change. This property is desirable for future resistive
switching devices. Amorphous lithium lanthanum titanate (a-LLTO) was originally
developed as a solid-state electrolyte with relatively high lithium ionic
conductivity and low electronic conductivity among oxide-type solid
electrolytes. However, it has been suggested that electric conductivity of
a-LLTO changes depending on oxygen content. In this work, the investigation of
switching behavior of a-LLTO was conducted by employing a range of voltage
sweep techniques, ultimately establishing a stable and optimal operating
condition within the voltage window of -3.5 V to 3.5 V. This voltage range
effectively balances the desirable trait of a substantial resistance change by
three orders of magnitude with the imperative avoidance of LLTO decomposition.
This switching behavior is also confirmed at nanodevice of Ni/LLTO/Ni through
in-situ biasing inside focused-ion beam/scanning electron microscope (FIB-SEM).
Experiment and computation with different LLTO composition shows that LLTO has
two distinct conductivity states due to Ti reduction. The distribution of these
two states is discussed using simplified binary model, implying the conductive
filament growth during low resistance state. Consequently, our study deepens
understanding of LLTO electronic properties and encourages the
interdisciplinary application of battery materials for resistive switching
devices. | 2310.00543v1 |
2019-03-28 | First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping | We present a new technology for the shaping of the electric field in Time
Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This
technology allows for the minimisation of passive material near the active
volume of the TPC and thus is capable to reduce background events originating
from radioactive decays or scattering on the material itself. Furthermore, the
high and continuous electric resistivity of the foil limits the power
dissipation per unit area and minimizes the risks of damages in the case of an
electric field breakdown. Replacing the conventional field cage with a
resistive plastic film structure called 'shell' decreases the number of
components within the TPC and therefore reduces the potential points of failure
when operating the detector. A prototype liquid argon (LAr) TPC with such a
resistive shell and with a cathode made of the same material was successfully
tested for long term operation with electric field values up to about 1.5
kV/cm. The experiment shows that it is feasible to successfully produce and
shape the electric field in liquefied noble-gas detectors with this new
technology. | 1903.11858v2 |
2023-02-24 | Antiferromagnetism of CeCd$_{0.67}$As$_{2}$ existing deep inside the narrow gap semiconducting state | Single crystals of $R$Cd$_{0.67}$As$_2$ ($R$ = La and Ce) have been
synthesized by high temperature ternary melt and their physical properties have
been explored by means of magnetization, specific heat, electrical resistivity,
Hall coefficient, and thermoelectric power measurements. $R$Cd$_{0.67}$As$_2$
compounds indicate a (structural) phase transition at high temperatures,
accompanied by a remarkable increase of the electrical resistivity with an
extremely low carrier concentration. CeCd$_{0.67}$As$_2$ exhibits a large
magnetic anisotropy and an antiferromagnetic (AFM) order below $T_{N} = 4$~K.
Magnetic susceptibility curves, together with magnetization isotherms and
specific heat, are analyzed by the point charge model of crystalline electric
field (CEF). In the paramagnetic state, the observed magnetic properties can be
well explained by the CEF effects, implying that the 4$f$ moments remain
localized. Electrical resistivity measurements, together with Hall resistivity
and thermoelectric power, also suggest highly localized 4$f$ electrons, where
Kondo contributions are negligible. The low temperature physical properties
manifest strong magnetic field dependencies. For $H \perp c$, $T_{N}$ shifts to
lower temperature as magnetic field increases, and eventually disappears at
$H_{c} \sim 60$~ kOe. Inside the AFM state, three metamagnetic transitions are
clearly evidenced from the magnetization isotherms. The RKKY interaction may be
responsible for the AFM ordering in CeCd$_{0.67}$As$_2$, however it would have
to be mediated by extremely low charge carriers. Although the AFM ordering
temperature in CeCd$_{0.67}$As$_2$ can be continuously suppressed to zero, no
AFM quantum phase transition is expected due to the lack of conduction electron
clouds to screen the 4$f$ moments. | 2302.12451v1 |
2003-05-06 | High Magnetic Field Sensor Using LaSb2 | The magnetotransport properties of single crystals of the highly anisotropic
layered metal LaSb2 are reported in magnetic fields up to 45 T with fields
oriented both parallel and perpendicular to the layers. Below 10 K the
perpendicular magnetoresistance of LaSb2} becomes temperature independent and
is characterized by a 100-fold linear increase in resistance between 0 and 45 T
with no evidence of quantum oscillations down to 50 mK. The Hall resistivity is
hole-like and gives a high field carrier density of n ~ 3x10^20 cm^-3. The
feasibility of using LaSb2 for magnetic field sensors is discussed. | 0305116v1 |
2016-12-30 | CdTe and CdZnTe Crystal Growth and Production of Gamma Radiation Detectors | Bridgman CdTe and CdZnTe crystal growth, with cadmium vapor pressure control,
is applied to production of semiconductor gamma radiation detectors. Crystals
are highly donor doped and highly electrically conducting. Annealing in
tellurium vapors transforms them into a highly compensated state of high
electrical resistance and high sensitivity to gamma radiation. N-type
detectors, equipped with ohmic contacts, and a grounded guard ring around the
positive contact, are not sensitive to hole trapping. Conductivity control, by
the doping level, optimizes the detector operation by trade-off between
electrons' lifetime and electrical resistance. Gamma spectra of single
detectors and detector arrays are presented. Detector optimization and gamma
detection mechanisms are discussed. | 1612.09571v1 |
2015-06-25 | Metallic multilayers for X-band Bragg reflector applications | We present a structural and high frequency (8.72GHz) electrical
characterization of sputter deposited Ti/W, Ti/Ru and Mo/Ti metallic
multilayers for potential application as acoustic Bragg reflectors. We prove
that all metallic multilayers comprised of different acoustic impedance metals
such as Ti, W, Mo are promising candidates for Bragg reflector/bottom electrode
in full X-band thin film acoustic resonators. Values for high frequency
resistivity of the order of $10^{-8} ohm.m$ are measured by use of a
contact-free/non-invasive sheet resistance method. | 1506.07702v1 |
2014-06-11 | Very high thermoelectric power factor in a Fe3O4/SiO2/p-type Si(100)heterostructure | The thermoelectric and transport properties of a Fe3O4/SiO2/p-Si(100)
heterostructure have been investigated between 100 and 300 K. Both Hall and
Seebeck coefficients change sign from negative to positive with increasing
temperature while the resistivity drops sharply due to tunneling of carriers
into the p-Si(100). The low resistivity and large Seebeck coefficient of Si
give a very high thermoelectric power factor of 25.5mW/K2m at 260K which is an
underestimated, lower limit value and is related to the density of states and
difference in the work functions of Fe3O4 and Si(100) that create an
accumulation of majority holes at the p-Si/SiO2 interface | 1406.2814v1 |
2002-10-10 | Effects of Pressure on Electron Transport and Local Structure of Manganites: Low to High Pressure Regime | The pressure dependence of the resistivity and structure of
La0.60Y0.07Ca0.33MnO3 has been explored in the pressure range from 1 atm to ~7
GPa. The metal to insulator transition temperature (TMI) was found to reach a
maximum and the resistivity achieves a minimum at ~3.8 GPa. Beyond this
pressure, TMI is reduced with a concomitant increase in the resistivity.
Structural measurements at room temperature show that at low pressure (below 2
GPa) the Mn-O bond lengths are compressed. Between ~2 and ~4 GPa, a pressure
induced enhancement of the Jahn-Teller (JT) distortion occurs in parallel with
an increase in Mn-O1-Mn bond angle to ~180 (degree). Above ~4 GPa, the Mn-O1-Mn
bond angle is reduced while the JT distortion appears to remain unchanged. The
resistivity above TMI is well modeled by variable range hopping. The pressure
dependence of the localization length follows the behavior of TMI. | 0210220v2 |
2003-07-31 | Is Room Temperature Superconductivity in Carbon Nanotubes Too Wonderful to Believe? | It is well known that copper-based perovskite oxides rightly enjoy consensus
as high-temperature superconductors on the basis of two signatures: Meissner
effect and zero resistance. In contrast, I provide over twenty signatures for
room temperature superconductivity in carbon nanotubes. The one-dimensionality
of the nanotubes complicates the right-of-passage for prospective
quasi-one-dimensional superconductors. The Meissner effect is less visible
because the diameters of nanotubes are much smaller than the penetration depth.
Zero resistance is less obvious because of the quantum contact resistance and
significant quantum phase slip, both of which are associated with a finite
number of transverse conduction channels. Nonetheless, on-tube resistance at
room temperature has been found to be indistinguishable from zero for many
individual multi-walled nanotubes. On the basis of more than twenty arguments,
I suggest that carbon nanotubes deserve to be classified as room temperature
superconductors. The mechanism for room-temperature superconductivity may arise
from strong electron-phonon and electron-plasmon coupling. | 0307770v3 |
2003-09-24 | High critical fields in MgB2 thin films with various resistivity values | In this paper, we analyze the upper critical field of four MgB2 thin films,
with different resistivity (between 5 to 50 mWcm) and critical temperature
(between 29.5 to 38.8 K), measured up to 28 Tesla. In the perpendicular
direction the critical fields vary from 13 to 24 T and we can estimate 42-57 T
range in other direction. We observe linear temperature dependence even at low
temperatures without saturation, in contrast to BCS theory. Considering the
multiband nature of the superconductivity in MgB2, we conclude that two
different scattering mechanisms influence separately resistivity and critical
field. In this framework, resistivity values have been calculated from Hc2(T)
curves and compared with the measured ones. | 0309543v1 |
2004-11-18 | Hysteretic current-voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO$_{3}$/SrTi$_{0.99}$Nb$_{0.01}$O$_{3}$ | Transport properties have been studied for a perovskite heterojunction
consisting of SrRuO$_{3}$ (SRO) film epitaxially grown on
SrTi$_{0.99}$Nb$_{0.01}$O$_{3}$ (Nb:STO) substrate. The SRO/Nb:STO interface
exhibits rectifying current-voltage ($I$-$V$) characteristics agreeing with
those of a Schottky junction composed of a deep work-function metal (SRO) and
an $n$-type semiconductor (Nb:STO). A hysteresis appears in the $I$-$V$
characteristics, where high resistance and low resistance states are induced by
reverse and forward bias stresses, respectively. The resistance switching is
also triggered by applying short voltage pulses of 1 $\mu$s - 10 ms duration. | 0411474v1 |
2005-09-13 | Evidence for High-Temperature Superconductivity in Doped Laser-Processed Sr-Ru-O | We have discovered that samples of a new material produced by special
processing of crystals of Sr2RuO4 (which is known to be a triplet
superconductor with Tc values ~1.0-1.5K) exhibit signatures of
superconductivity (zero DC resistance and expulsion of magnetic flux) at
temperatures exceeding 200K. The special processing includes deposition of a
silver coating and laser micromachining; Ag doping and enhanced oxygen are
observed in the resultant surface layer. The transition, whether measured
resistively or by magnetic field expulsion, is broad. When the transition is
registered by resistive methods, the critical temperature is markedly reduced
when the measuring current is increased. The resistance disappears by about
190K. The highest value of Tc registered by magneto-optical visualization is
about 220K and even higher values (up to 250K) are indicated from the
SQUID-magnetometer measurements. | 0509313v1 |
2006-05-04 | Threshold Resistance in the DC Josephson Effect | We show that SIS Josephson junctions have a threshold resistance, above which
the Josephson coupling and the supercurrents become extremely small, due to the
shrinking of the Cooper pair size during the Josephson tunneling. Accordingly,
the threshold resistance is smaller for higher Tc superconductors with small
Cooper pair size and for the insulating barrier with higher resistance. This
understanding agrees with the observations in SIS junctions of low Tc
superconductors, such as Sn, Pb, and Nb. For MgB2 it explains why the big gap
does not show the supercurrents, unlike the small gap. Furthermore, it is
consistent with the fact that high Tc cuprates show the Josephson effects only
for SNS type junctions, including the intrinsic Josephson effects. | 0605122v1 |
2007-04-03 | Scaling of Resistance and Electron Mean Free Path of Single-Walled Carbon Nanotubes | We present an experimental investigation on the scaling of resistance in
individual single walled carbon nanotube devices with channel lengths that vary
four orders of magnitude on the same sample. The electron mean free path is
obtained from the linear scaling of resistance with length at various
temperatures. The low temperature mean free path is determined by impurity
scattering, while at high temperature the mean free path decreases with
increasing temperature, indicating that it is limited by electron-phonon
scattering. An unusually long mean free path at room temperature has been
experimentally confirmed. Exponentially increasing resistance with length at
extremely long length scales suggests anomalous localization effects. | 0704.0300v2 |
2007-09-12 | Thermal Transient Characterization of Packaged Thin Film Microcoolers | A network identification by deconvolution (NID) method is applied to the
thermal transient response of packaged and unpackaged microcoolers. A thin film
resistor on top of the device is used as the heat source and the temperature
sensor. The package and the bonding thermal resistances can be easily
identified by comparing structure functions. High-speed coplanar probes are
used to achieve a short time resolution of roughly 100ns in the transient
temperature response. This is used to separate the thermal properties of the
thin film from the substrate. The obtained thermal resistances of the buffer
layer and Silicon substrate are consistent with the theoretical calculations.
In order to estimate the superlattice thermal resistance and separate it from
the thin SiNx layer deposited underneath the thin film resistive sensor, an
order of magnitude faster thermal transient response is needed. | 0709.1817v1 |
2007-12-09 | Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic semiconductors | The presence of localized spins exerts a strong influence on quantum
localization in doped semiconductors. At the same time carrier-mediated
interactions between the localized spins are modified or even halted by
carriers' localization. The interplay of these effects is discussed for II-VI
and III-V diluted magnetic semiconductors. This insight is exploited to
interpret the complex dependence of resistance on temperature, magnetic field,
and concentration of valence-band holes in (Ga,Mn)As. In particular, high field
negative magnetoresistance results from the orbital weak localization effect.
The resistance maximum and the associated negative magnetoresistance near the
Curie temperature are assigned to the destructive influence of preformed
ferromagnetic bubbles on the "antilocalization" effect driven by
disorder-modified carrier-carrier interactions. These interactions account also
for the low-temperature increase of resistance. Furthermore, the sensitivity of
conductance to spin splitting and to scattering by spin disorder may explain
resistance anomalies at coercive fields, where relative directions of external
and molecular fields change. | 0712.1293v2 |
2009-08-25 | Bipolar resistive switching in amorphous titanium oxide thin films | Using isothermal and temperature-dependent electrical measurements, we
investigated the resistive switching mechanism of amorphous titanium oxide thin
films deposited by a plasma-enhanced atomic layer deposition method between two
aluminum electrodes. We found a bipolar resistive switching behavior in the
high temperature region (> 140 K), and two activation energies of shallow
traps, 0.055 eV and 0.126 eV in the ohmic current regime. We also proposed that
the bipolar resistive switching of amorphous TiO2 thin films is governed by the
transition of conduction mode from a bulk-limited SCLC model (Off state) to an
interface-limited Schottky emission (On state), generated by the ionic movement
of oxygen vacancies. | 0908.3525v1 |
2009-12-09 | Scaling Properties of Ge-SixGe1-x Core-Shell Nanowire Field Effect Transistors | We demonstrate the fabrication of high-performance Ge-SixGe1-x core-shell
nanowire field-effect transistors with highly doped source and drain, and
systematically investigate their scaling properties. Highly doped source and
drain regions are realized by low energy boron implantation, which enables
efficient carrier injection with a contact resistance much lower than the
nanowire resistance. We extract key device parameters, such as intrinsic
channel resistance, carrier mobility, effective channel length, and external
contact resistance, as well as benchmark the device switching speed and ON/OFF
current ratio. | 0912.1827v1 |
2010-07-21 | The effects of superconductor-stabilizer interfacial resistance on quench of a pancake coil made out of coated conductor | We present the results of numerical analysis of normal zone propagation in a
stack of $YBa_2Cu_3O_{7-x}$ coated conductors which imitates a pancake coil.
Our main purpose is to determine whether the quench protection quality of such
coils can be substantially improved by increased contact resistance between the
superconducting film and the stabilizer. We show that with increased contact
resistance the speed of normal zone propagation increases, the detection of a
normal zone inside the coil becomes possible earlier, when the peak temperature
inside the normal zone is lower, and stability margins shrink. Thus, increasing
contact resistance may become a viable option for improving the prospects of
coated conductors for high $T_c$ magnets applications. | 1007.3768v2 |
2012-10-15 | Bi2Te_xSe_y series studied by resistivity and thermopower | We study the detailed temperature and composition dependence of the
resistivity, $\rho(T)$, and thermopower, $S(T)$, for a series of layered
bismuth chalcogenides Bi$_2$Te$_{3-x}$Se$_x$, and report the stoichiometry
dependence of the optical band gap. In the resistivity of the most compensated
member, Bi$_2$Te$_{2.1}$Se$_{0.9}$, we find a low-temperature plateau whose
onset temperature correlates with the high-temperature activation energy. For
the whole series $S(T)$ can be described by a simple model for an extrinsic
semiconductor. By substituting Se for Te, the Fermi level is tuned from the
valence band into the conduction band. The maximum values of $S(T)$, bulk band
gap as well the activation energy in the resistivity are found for $x \approx
0.9$. | 1210.3901v3 |
2014-07-14 | Multistate nonvolatile straintronics controlled by a lateral electric field | We present a multifunctional and multistate permanent memory device based on
lateral electric field control of a strained surface. Sub-coercive electrical
writing of a remnant strain of a PZT substrate imprints stable and rewritable
resistance changes on a CoFe overlayer. A proof-of-principle device, with the
simplest resistance strain gage design, is shown as a memory cell exhibiting
17-memory states of high reproducibility and reliability for nonvolatile
operations. Magnetoresistance of the film also depends on the cell state, and
indicates a rewritable change of magnetic properties persisting in the remnant
strain of the substrate. This makes it possible to combine strain, magnetic and
resistive functionalities in a single memory element, and suggests that
sub-coercive stress studies are of interest for straintronics applications. | 1407.3651v2 |
2015-10-29 | Resistive superconducting transition and effects of atmospheric exposure in the intercalation superconductor Ax(C2H8N2)yFe2-zSe2 (A = Li, Na) | We have succeeded in observing zero-resistivity in newly discovered
intercalation superconductors Ax(C2H8N2)yFe2-zSe2 (A = Li, Na) with Tc = 45 K,
using the sintered pellet samples. The electrical resistivity, \r{ho}, in the
normal state is metallic and Tconset defined in the $\rho$ measurements, is as
high as ~ 57 K. We have also investigated effects of the atmospheric exposure
in Lix(C2H8N2)yFe2-zSe2. It has been found that both the crystal structure and
superconductivity are maintained at least up to several days, indicating this
material is comparatively resistant to the atmospheric exposure. | 1510.08629v1 |
2016-05-19 | Resistive Switching Characteristics of Al/Si3N4/p-Si MIS-Based Resistive Switching Memory Devices | In this study, we proposed and demonstrated a self-rectifying property of
silicon nitride (Si3N4)-based resistive random access memory device by
employing p-type silicon (p-Si) as bottom electrode. The RRAM devices consisted
of Al/Si3N4/p-Si are fabricated by a low presure chemical vapor deposition and
exhibited an intrinsic diode property with non-linear current-voltage (I-V)
behavior. In addition, compared to conventional metal/insulator/metal (MIM)
structure of Al/Si3N4/Ti RRAM cells, operating current in whole bias regions
for proposed metal/insulator/semiconductor (MIS) cells has been dramatically
lowered because introduced p-Si bottom electrode efficiently suppresses the
current in both low and high resistive states. As a result, the results mean
that by employing p-Si as bottom electrode the Si3N4-based RRAM cells can be
applied to selector-free RRAM cells. | 1605.06006v1 |
2016-06-25 | Transport mechanism through metal-cobaltite interfaces | The resistive switching (RS) properties as a function of temperature were
studied for Ag/La$_{1-x}$Sr$_x$CoO$_3$ (LSCO) interfaces. The LSCO is a
fully-relaxed 100 nm film grown by metal organic deposition on a LaAlO$_3$
substrate. Both low and a high resistance states were set at room temperature
and the temperature dependence of their current-voltage (IV) characteristics
was mea- sured taking care to avoid a significant change of the resistance
state. The obtained non-trivial IV curves of each state were well reproduced by
a circuit model which includes a Poole-Frenkel element and two ohmic
resistances. A microscopic description of the changes produced by the RS is
given, which enables to envision a picture of the interface as an area where
conductive and insulating phases are mixed, producing Maxwell-Wagner
contributions to the dielectric properties. | 1606.07974v1 |
2016-07-19 | Non-quasiparticle transport and resistivity saturation: A view from the large-N limit | The electron dynamics in metals are usually well described by the
semiclassical approximation for long-lived quasiparticles. However, in some
metals, the scattering rate of the electrons at elevated temperatures becomes
comparable to the Fermi energy; then, this approximation breaks down, and the
full quantum-mechanical nature of the electrons must be considered. In this
work, we study a solvable, large-$N$ electron-phonon model, which at high
temperatures enters the non-quasiparticle regime. In this regime, the model
exhibits "resistivity saturation" to a temperature-independent value of the
order of the quantum of resistivity - the first analytically tractable model to
do so. The saturation is not due to a fundamental limit on the electron
lifetime, but rather to the appearance of a second conductivity channel. This
is suggestive of the phenomenological "parallel resistor formula", known to
describe the resistivity of a variety of saturating metals. | 1607.05725v1 |
2016-11-04 | Origin of multistate resistive switching in Ti/manganite/Si$O_x$/Si heterostructures | We report on the growth and characterization of
Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/Si$O_x$/n-Si memristive devices. We demonstrate
that using current as electrical stimulus unveils an intermediate resistance
state, in addition to the usual high and low resistance states that are
observed in standard voltage controlled experiments. Based on thorough
electrical characterization (impedance spectroscopy, current-voltage curves
analysis), we disclose the contribution of three different microscopic regions
of the device to the transport properties: an ohmic incomplete metallic
filament, a thin manganite layer below the filament tip exhibiting
Poole-Frenkel like conduction, and the SiOx layer with an electrical response
well characterized by a Child-Langmuir law. Our results suggest that the
existence of the SiOx layer plays a key role in the stabilization of the
intermediate resistance level, indicating that the combination of two or more
active RS oxides adds functionalities in relation to single-oxide devices. We
understand that these multilevel devices are interesting and promising as their
fabrication procedure is rather simple and they are fully compatible with
standard Si-based electronics. | 1611.01552v2 |
2017-06-07 | Spatially Resolved Thermometry of Resistive Memory Devices | The operation of resistive and phase-change memory (RRAM and PCM) is
controlled by highly localized self-heating effects, yet detailed studies of
their temperature are rare due to challenges of nanoscale thermometry. Here we
show that the combination of Raman thermometry and scanning thermal microscopy
(SThM) can enable such measurements with high spatial resolution. We report
temperature-dependent Raman spectra of HfO$_2$, TiO$_2$ and Ge$_2$Sb$_2$Te$_5$
(GST) films, and demonstrate direct measurements of temperature profiles in
lateral PCM devices. Our measurements reveal that electrical and thermal
interfaces dominate the operation of such devices, uncovering a thermal
boundary resistance of 30 m$^2$K$^{-1}$GW$^{-1}$ at GST-SiO$_2$ interfaces and
an effective thermopower 350 $\mu$V/K at GST-Pt interfaces. We also discuss
possible pathways to apply Raman thermometry and SThM techniques to nanoscale
and vertical resistive memory devices. | 1706.02318v1 |
2017-12-03 | Microstructure and properties of Cu-Sn-Zn-TiO2 Nano-composite coatings on mild steel | Cu-Sn-Zn coatings have been widely used in industry for their unique
properties, such as good conductivity, high corrosion resistance and excellent
solderability. To further improve the mechanical performance of Cu-Sn-Zn
coatings, powder-enhanced method was applied in the current study and
Cu-Sn-Zn-TiO2 nano-composite coatings with different TiO2 concentration were
fabricated. The microstructure of Cu-Sn-Zn-TiO2 nano-composite coatings were
investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM).
The mechanical properties of coatings including microhardness and wear
resistance were studied. The results indicate that the incorporation of TiO2
nanoparticle can significantly influence the properties of Cu-Sn-Zn coatings.
The microhardness of Cu-Sn-Zn coating was increased to 383 HV from 330 HV with
1g/L TiO2 addition. Also, the corrosion resistance of coating was enhanced. The
effects of TiO2 nanoparticle concentration on the microstructure, mechanical
properties and corrosion resistance of Cu-Sn-Zn-TiO2 nano-composite coatings
were discussed. | 1712.00853v1 |
2022-02-11 | Comparison of the charge-crystal and charge-glass state in geometrically frustrated organic conductors studied by fluctuation spectroscopy | We present a systematic investigation of the low-frequency charge carrier
dynamics in different charge states of the organic conductors
$\theta$-(BEDT-TTF)$_2$$M$Zn(SCN)$_4$ with $M$=Rb,Tl, which result from
quenching or relaxing the charge degrees of freedom on a geometrically
frustrated triangular lattice. Due to strong electronic correlations these
materials exhibit a charge-ordering transition, which can be kinetically
avoided by rapid cooling resulting in a so-called charge-glass state without
long-range order. The combination of fluctuation spectroscopy and a heat pulse
method allows us to study and compare the resistance fluctuations in the
low-resistive quenched and the high-resistive charge-ordered state, revealing
striking differences in the respective noise magnitudes. For both compounds, we
find strongly enhanced resistance fluctuations right at the metal-insulator
transition and a broad noise maximum in the slowly cooled charge-crystal state
with partly dominating two-level processes revealing characteristic activation
energies. | 2202.05602v1 |
2007-10-09 | Strong reduction of field-dependent microwave surface resistance in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ with sub-micrometric BaZrO$_3$ inclusions | We observe a strong reduction of the field induced thin film surface
resistance measured at high microwave frequency ($\nu=$47.7 GHz) in
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films grown on SrTiO$_3$ substrates, as a
consequence of the introduction of sub-micrometric BaZrO$_3$ particles. The
field increase of the surface resistance is smaller by a factor of $\sim$3 in
the film with BaZrO$_3$ inclusions, while the zero-field properties are not
much affected. Combining surface resistance and surface reactance data we
conclude (a) that BaZrO$_3$ inclusions determine very deep and steep pinning
wells and (b) that the pinning changes nature with respect to the pure film. | 0710.1754v1 |
2017-08-04 | Tunable Spin-Orbit Torques in Cu-Ta Binary Alloy Heterostructures | The spin Hall effect (SHE) is found to be strong in heavy transition metals
(HM), such as Ta and W, in their amorphous and/or high resistivity form. In
this work, we show that by employing a Cu-Ta binary alloy as buffer layer in an
amorphous Cu$_{100-x}$Ta$_{x}$-based magnetic heterostructure with
perpendicular magnetic anisotropy (PMA), the SHE-induced damping-like
spin-orbit torque (DL-SOT) efficiency $|\xi_{DL}|$ can be linearly tuned by
adjusting the buffer layer resistivity. Current-induced SOT switching can also
be achieved in these Cu$_{100-x}$Ta$_{x}$-based magnetic heterostructures, and
we find the switching behavior better explained by a SOT-assisted domain wall
propagation picture. Through systematic studies on Cu$_{100-x}$Ta$_{x}$-based
samples with various compositions, we determine the lower bound of spin Hall
conductivity
$|\sigma_{SH}|\approx2.02\times10^{4}[\hbar/2e]\Omega^{-1}\cdot\operatorname{m}^{-1}$
in the Ta-rich regime. Based on the idea of resistivity tuning, we further
demonstrate that $|\xi_{DL}|$ can be enhanced from 0.087 for pure Ta to 0.152
by employing a resistive TaN buffer layer. | 1708.01356v1 |
2019-03-29 | Effect of synthesis conditions on the electrical resistivity of TiSe$_2$ | Dilute impurities and growth conditions can drastically affect the transport
properties of TiSe$_2$, especially below the charge density wave transition. In
this paper, we discuss the effects of cooling rate, annealing time and
annealing temperature on the transport properties of TiSe$_2$: slow cooling of
polycrystalline TiSe$_2$ post-synthesis drastically increases the low
temperature resistivity, which is in contrast to the metallic behavior of
single-crystalline TiSe$_2$ due to charge doping from the residual iodine
transport agent. A logarithmic increase of resistivity upon cooling and
negative magnetoresistance with a sharp cusp around zero field are observed for
the first time for the polycrystalline TiSe$_2$ samples, pointing to
weak-localization effects due to low dimensionality. Annealing at low
temperatures has a similar, but less drastic effect. Furthermore, rapid
quenching of the polycrystalline samples from high temperatures freezes in
disorder, leading to a decrease in the low temperature resistivity. | 1903.12375v3 |
2019-12-18 | A theory of resistivity in Kondo lattice materials: the memory function approach | We theoretically analyse D.C. resistivity($\rho$) in the Kondo-lattice model
using the powerful memory function approach. The complete temperature evolution
of $\rho$ is investigated using the W\"{o}lfle-G\"{o}tze expansion of the
memory function. The resistivity in this model originates due to spin-flip
magnetic scattering of conduction $s$-electron off the quasi-localized $d$ or
$f$ electron spins. We find the famous resistivity upturn at lower temperature
regime ($k_B T<<\mu_d$), where $\mu_d$ is the effective chemical potential of
$d$-electrons. In the high temperature regime $(\mu_d<<k_B T)$ we discover that
$\rho \propto T^{\frac{3}{2}}$. The worked out theory is quantitatively
compared with experimental data and reasonably good agreement is found. | 1912.08407v1 |
2019-06-15 | Oxide layer thickness effects on the resistance switching characteristics of Ti/TiO2-NT/Au structure | Self-ordered nanotubular titania TiO2-NT with outer tube diameter of 45 nm
are synthesized using the anodic oxidation of titanium foil. Four sets of
memristors with 100 ${\mu}m$ diameter based on Ti/TiO2-NT/Au sandwich
structures with an oxide layer thickness of 80, 120, 160 and 200 nm are
fabricated. Current-voltage (CV) characteristics for the obtained samples in
the static and dynamic operation modes are studied. Resistance in high and low
resistance states is estimated. Basing on the analysis of the CV
characteristics in dynamic mode (> 14 000 switchings) a prospective of use for
synthesized Ti/TiO2-NT/Au micromemristors with oxide layer thickness of 160 nm
in non-volatile memory is shown.
Keywords: anodic titania, titanium dioxide nanotubes, nanotubular structure,
memristor, resistive switching | 1906.06555v1 |
2019-11-28 | Tailored joint fabrication process derived ultra-low resistance MgB2 superconducting joint | We report an ultra-low resistance superconducting joint using unreacted
multifilament MgB2 wires produced by tailoring the powder compaction pressure
within the joint with heat treatment conditions. The joint demonstrated an
ultra-low resistance of 5.48 x 10^-15 ohms and critical current (Ic) of 91.3 A
at 20 K in self-field. The microstructural and composition studies of the joint
revealed cracks and a high amount of MgO, respectively. These two features
reduced the Ic of the joint to some extent; nevertheless, the joint resistance
was not affected by it. Our tailored joining process will play a pivotal role
in superconducting joint development. | 1911.12645v1 |
2020-10-23 | Improvement of HRS Variability in OxRRAM by Tailored Metallic Liner | In this work, we propose a novel integration in order to significantly reduce
the High Resistance State vari-ability and to improve thermal stability in
Oxide-based Resistive Random Access Memory (OxRRAM) devices. A novel device
featuring a metallic liner, acting as a parallel resistance, is presented. To
assess the effect of this solution, we compare the results with a standard
OxRRAM cell structure. A very good stability of the resistive states, both in
endurance and temperature, is highlighted and explained thanks to a conductive
fila-ment based model. | 2010.12210v1 |
2020-11-01 | Light induced resistive switching in copper oxide thin films | Copper oxide thin film based metal-insulator-metal structures were subjected
to white light irradiation.The top electrodes included Al, Cr and Ni while the
bottom electrode was either Au or Pt. A white light pulse controls the set
process and this light induced set (LIS) can be performed at very low voltages
(tens of milli volts) which is not possible in the normal set process. The LIS
is initiated at the positive edge of the pulse and there is no effect of the
falling edge of the light. In most cases the high resistance state (HRS) to low
resistance state (LRS) transition is irreversible i.e.the devices continue to
remain in the LRS even after the light pulse is switched off. Light induced
reset (LIR) is achieved in only one device structure Al/CuxO/Au. By using LIS
and LIR, set and reset power of the device can be reduced to a great extent and
the set and reset parameters variation also reduces. The current work, thus,
points to the possibility of formation and compliance-free resistive random
access memory devices. | 2011.00423v1 |
2021-04-05 | Charge density wave and finite-temperature transport in minimally twisted bilayer graphene | We study phenomena driven by electron-electron interactions in the minimally
twisted bilayer graphene (mTBLG) with a perpendicular electric field. The
low-energy degrees of freedom in mTBLG are governed by a network of
one-dimensional domain-wall states, described by two channels of
one-dimensional linearly dispersing spin-1/2 fermions. We show that the
interaction can realize a spin-gapped inter-channel charge density wave (CDW)
state at low temperatures, forming a "Coulomb drag" between the channels and
leaving only one charge conducting mode. For sufficiently high temperatures,
power-law-in-temperature resistivity emerges from the charge umklapp
scatterings within a domain wall. Remarkably, the presence of the CDW states
can strengthen the charge umklapp scattering and induce a resistivity minimum
at an intermediate temperature corresponding to the CDW correlation energy. We
further discuss the conditions that resistivity of the network is dominated by
the domain walls. In particular, the power-law-in-temperature resistivity
results can apply to other systems that manifest topological domain-wall
structures. | 2104.02084v2 |
2021-05-14 | Mechanical Response of Mesoporous Amorphous NiTi Alloy to External Deformations | The porous titanium nickelide is very popular in various industries due to
unique combination of physical and mechanical properties such as shape memory
effect, high corrosion resistance, and biocompatibility. The non-equilibrium
molecular dynamics simulation was applied to study the influence of porosity
degree on mechanical properties of porous amorphous titanium nickelide at
uniaxial tension, uniaxial compression, and uniform shear. We have found that
the porous amorphous alloy is characterized by a relatively large value of
Young's modulus in comparison to its crystalline analogue. It has been found
that the system with a percolated network of pores exhibits improved elastic
characteristics associated with resistance to tensile and shear. The system
contained isolated spherical pores is more resistant to compression and less
resistant to tensile and shear. These results can be applied to develop and
improve the methods for making amorphous metal foams. | 2105.06693v1 |
2021-08-01 | Sb concentration dependent Structural and Transport properties of Polycrystalline (Bi1-xSbx)2Te3 Mixed crystal | (Bi1-xSbx)2Te3 (x=0.60, 0.65, 0.68, 0.70, 0.75 and 0.80) mixed crystals have
been synthesized by solid state reaction. In depth structural, thermal,
transport and electronic properties are reported. Defect and disorder play a
crucial role in structural and transport behaviour. Disorder induced
iso-structural phase transition is observed at x=0.70, which is supported by
the structural and transport properties data. Debye temperature has been
estimated from the powder diffraction data. Differential scanning calorimetry
(DSC) data confirms the glass transition in the material. Low temperature
resistivity data shows Variable range hopping mechanism whereas high
temperature data follows activated behaviour. Activation energy is calculated
from the semiconducting region of resistivity data. Both Hall measurement and
temperature dependent thermopower data (S(T)) confirms that samples are p-type
in nature. Density of state effective mass has been estimated from Pisarenko
relation and corroborated with resistivity data. Thermal conductivity (k) is
estimated using experimentally obtained data. Figure of Merit (ZT) of the
synthesized samples are calculated using resistivity, S(T) and k. Structural
and transport properties are correlated, confirms the transition from disorder
to order state. Defect and disorder are corroborated with structural and
Thermoelectric properties of the synthesized samples. | 2108.00525v1 |
2021-10-16 | Topological phonons in an inhomogeneously strained silicon-6: Possible evidence of the high temperature spin superfluidity and the second sound of topological phonons | The superposition of topological phonons and flexoelectronic charge
separation in an inhomogeneously strain Si give rise to topological electronic
magnetism of phonons. The topological electronic magnetism of phonons is also
expected to give rise to stationary spin current or spin superfluidity. In this
experimental study, we present possible evidence of spin superfluidity in an
inhomogeneously strained p-Si thin films samples. The spin superfluidity is
uncovered using non-local resistance measurement. A resonance behavior is
observed in a non-local resistance measurement at 10 kHz and between 270 K and
281.55 K, which is attributed to the second sound. The observation of second
sound and spatially varying non-local resistance phase are the evidences for
spin superfluidity. The spatially varying non-local resistance with opposite
phase are also observed in Pt/MgO/p-Si sample. The overall non-local responses
can be treated as a standing waveform from temporal magnetic moments of the
topological phonons. | 2110.08431v1 |
2021-12-10 | Transport in the emergent Bose liquid: Bad metal, strange metal, and weak insulator, all in one system | Non-saturating high-temperature resistivity ("bad metal"), T-linear
low-temperature resistivity ("strange metal"), and a crossover to
activation-free growth of the resistivity in the low-temperature limit ("weak
insulator") are among the most exotic behaviors widely observed in many
strongly correlated materials for decades that defy the standard Fermi liquid
description of solids. Here we investigate these puzzling behaviors by
computing temperature-dependent optical conductivity of an emergent Bose liquid
and find that it reproduces all the unexplained features of the experiments,
including a featureless continuum and a well-known mid-infrared peak. Amazingly
and with physically intuitive mechanisms, the corresponding doping- and
temperature-dependent resistivity displays the bad metal and strange metal
simultaneously and sometimes weak insulating behaviors as well. The unification
of all these non-Fermi liquid behaviors in a single model suggests that a new
quantum state of matter, namely the emergent Bose liquid, will guide the
development of the next generation of solid state physics. | 2112.05747v1 |
2022-04-20 | Electrical breakdown in Thick-GEM based WELL detectors | The occurrence of electrical discharges in gas detectors restricts their
dynamic range and degrades their performance. Among the different methods
developed to mitigate discharge effects, the use of resistive materials in the
detector assembly was found to be very effective. In this work, we present the
results of a comparative study of electrical discharges in Thick-GEM-based
WELL-type detectors - with and without resistive elements. We present a new
method to measure discharges in the resistive-detector configurations; it
allows demonstrating, for the first time, the occurrence of discharges also in
the Resistive-Plate WELL detector configuration. It also provides direct
evidence for the Raether limit. | 2204.09445v2 |
2022-11-27 | Evolution of Resistive Switching Characteristics in WO3-x-based MIM Devices by Tailoring Oxygen Deficiency | We report on resistive switching (RS) characteristics of W/WO3-x/Pt-based
thin film memristors modulated by precisely controlled oxygen
non-stoichiometry. RS properties of the devices with varied oxygen vacancy (VO)
concentration have been studied by measuring their DC current voltage
properties. Switchability of the resistance states in the memristors have been
found to depend strongly on the VOs concentration in the WO3-x layer. Depending
on x, the memristors exhibited forming-free bipolar, forming-required bipolar
and non-formable characteristics. Devices with high VOs concentration (~1*1021
cm-3) exhibited lower initial resistance and memory window of only 15, which
has been increased to ~6500 with reducing VOs concentration to ~5.8*1020 cm-3.
Forming-free, stable RS with memory window of ~2000 have been realized for a
memristor possessing VOs concentration of ~6.2*1020 cm-3. Investigation of the
conduction mechanism suggests that tailoring VOs concentration modifies the
formation and dimension of the conducting filaments as well as the Schottky
barrier height at WO3-x/Pt interface which deterministically modulates RS
characteristics of the WO3-x based memristors. | 2211.14809v1 |
2024-05-13 | Durability of MgO/hydromagnesite mortars -- Resistance to chlorides and corrosion | The durability of MgO/hydromagnesite mortars was studied with respect to
their corrosion performance and resistance to chloride attack and moisture.
MgO/hydromagnesite pastes were cured in chloride solution to induce potential
formation of Mg-chlorides; however, no such phases were observed. Rapid
chloride ingress measurements demonstrated high penetration resistance and low
chloride migration coefficients, i.e. D_Cl = 1e-13 to 1e-12 m^2/s. The
corrosion rate of carbon steel embedded in MgO/HY mortars, as determined by
linear polarization resistance measurements, was in the range icorr = 1e-9
A/cm^2 in dry and 1e-7 A/cm^2 in wet conditions, irrespective of the mortar
composition or curing condition.These findings corroborate the hypothesis that,
in the absence of chlorides, the moisture condition is the primary predictor of
corrosion rate of carbon steel in the MgO/hydromagnesite binder. These
accelerated, short-term experiments suggest that the binder may be suited to
protect embedded carbon steel from corrosion under specific exposure conditions
of practical relevance. | 2405.08164v1 |
2024-05-27 | Electronic thermal resistivity and quasi-particle collision cross-section in semi-metals | Electron-electron collisions lead to a T-square component in the electrical
resistivity of Fermi liquids. The case of liquid $^3$He illustrates that the
\textit{thermal} resitivity of a Fermi liquid has a T-square term, expressed in
m$\cdot$W$^{-1}$. Its natural units are $\hbar/k_FE_F^2$. Here, we present a
high-resolution study of the thermal conductivity in bismuth, employing
magnetic field to extract the tiny electronic component of the total thermal
conductivity and resolving signals as small as $\approx 60 \mu$K. We find that
the electronic thermal resistivity follows a T-square temperature dependence
with a prefactor twice larger than the electric T-square prefactor. Adding this
information to what has been known for other semi-metals, we find that the
prefactor of the T-square thermal resistivity scales with the square of the
inverse of the Fermi temperature, implying that the dimensionless
fermion-fermion collision cross-section is roughly proportional to the Fermi
wavelength, indicating that it is not simply set by the strength of the Coulomb
interaction. | 2405.16984v2 |
2017-10-02 | Anomalous magnetotransport properties of high-quality single crystals of Weyl semimetal WTe2: Sign change of Hall resistivity | We report on a systematic study of Hall effect using high quality single
crystals of type-II Weyl semimetal WTe2 with the applied magnetic field B//c.
The residual resistivity ratio of 1330 and the large magnetoresistance of
1.5\times10^6 % in 9 T at 2 K, being in the highest class in the literature,
attest to their high quality. Based on a simple two-band model, the densities
(n_e and n_h) and mobilities (\mu_e and \mu_h) for electron and hole carriers
have been uniquely determined combining both Hall- and electrical-resistivity
data. The difference between ne and nh is ~1% at 2 K, indicating that the
system is in an almost compensated condition. The negative Hall resistivity
growing rapidly below ~20 K is due to a rapidly increasing \mu_h/\mu_e
approaching one. Below 3 K in a low field region, we found the Hall resistivity
becomes positive, reflecting that \mu_h/\mu_e finally exceeds one in this
region. These anomalous behaviors of the carrier densities and mobilities might
be associated with the existence of a Lifshitz transition and/or the spin
texture on the Fermi surface. | 1710.00570v1 |
2021-10-14 | Superconductor-insulator transitions in three-dimensional indium-oxide at high pressures | Experiments investigating magnetic-field-tuned superconductor-insulator
transition (HSIT) mostly focus on two-dimensional material systems where the
transition and its proximate ground-state phases, often exhibit features that
are seemingly at odds with the expected behavior. Here we present a
complementary study of a three-dimensional pressure-packed amorphous
indium-oxide (InOx) powder where granularity controls the HSIT. Above a low
threshold pressure of ~0.2 GPa, vestiges of superconductivity are detected,
although neither a true superconducting transition nor insulating behavior are
observed. Instead, a saturation at very high resistivity at low pressure is
followed by saturation at very low resistivity at higher pressure. We identify
both as different manifestations of anomalous metallic phases dominated by
superconducting fluctuations. By analogy with previous identification of the
low resistance saturation as a "failed superconductor", our data suggests that
the very high resistance saturation is a manifestation of a "failed insulator".
Above a threshold pressure of ~6 GPa, the sample becomes fully packed, and
superconductivity is robust, with TC tunable with pressure. A quantum critical
point at PC~25 GPa marks the complete suppression of superconductivity. For a
finite pressure below PC, a magnetic field is shown to induce a HSIT from a
true zero-resistance superconducting state to a weakly insulating behavior.
Determining the critical field, HC, we show that similar to the 2D behavior,
the insulating-like state maintains a superconducting character, which is
quenched at higher field, above which the magnetoresistance decreases to its
fermionic normal state value. | 2110.07251v3 |
2012-07-26 | High pressure transport studies of the LiFeAs analogues CuFeTe2 and Fe2As | We have synthesized two iron-pnictide/chalcogenide materials, CuFeTe2 and
Fe2As, which share crystallographic features with known iron-based
superconductors, and carried out high-pressure electrical resistivity
measurements on these materials to pressures in excess of 30 GPa. Both
compounds crystallize in the Cu2Sb-type crystal structure that is
characteristic of LiFeAs (with CuFeTe2 exhibiting a disordered variant). At
ambient pressure, CuFeTe2 is a semiconductor and has been suggested to exhibit
a spin-density-wave transition, while Fe2As is a metallic antiferromagnet. The
electrical resistivity of CuFeTe2, measured at 4 K, decreases by almost two
orders of magnitude between ambient pressure and 2.4 GPa. At 34 GPa, the
electrical resistivity decreases upon cooling the sample below 150 K,
suggesting the proximity of the compound to a metal-insulator transition.
Neither CuFeTe2 nor Fe2As superconduct above 1.1 K throughout the measured
pressure range. | 1207.6272v1 |
2012-10-12 | Pressure Induced Superconductivity in Ba0.5Sr0.5Fe2As2 | High-pressure electrical resistance measurements have been performed on
single crystal Ba0.5Sr0.5Fe2As2 platelets to pressures of 16 GPa and
temperatures down to 10 K using designer diamond anvils under quasi-hydrostatic
conditions with an insulating steatite pressure medium. The resistance
measurements show evidence of pressure-induced superconductivity with an onset
transition temperature at ~31 K and zero resistance at ~22 K for a pressure of
3.3 GPa. The transition temperature decreases gradually with increasing in
pressure before completely disappearing for pressures above 12 GPa. The present
results provide experimental evidence that a solid solution of two 122-type
materials, e.g., Ba1-x.SrxFe2As2 (0 < x <1), can also exhibit superconductivity
under high pressure | 1210.3603v1 |
2012-12-03 | Observation of Resistively Detected Hole Spin Resonance and Zero-field Pseudo-spin Splitting in Epitaxial Graphene | Electronic carriers in graphene show a high carrier mobility at room
temperature. Thus, this system is widely viewed as a potential future
charge-based high-speed electronic-material to complement- or replace- silicon.
At the same time, the spin properties of graphene have suggested improved
capability for spin-based electronics or spintronics, and spin-based quantum
computing. As a result, the detection, characterization, and transport of spin
have become topics of interest in graphene. Here we report a microwave
photo-excited transport study of monolayer and trilayer graphene that reveals
an unexpectedly strong microwave-induced electrical-response and dual
microwave-induced resonances in the dc-resistance. The results suggest the
resistive detection of spin resonance, and provide a measurement of the
g-factor, the spin relaxation time, and the sub-lattice degeneracy-splitting at
zero-magnetic-field. | 1212.0329v1 |
2013-04-09 | Upper critical field of high quality single crystals of KFe$_2$As$_2$ | Measurements of temperature-dependent in-plane resistivity, $\rho(T)$, were
used to determine the upper critical field and its anisotropy in high quality
single crystals of stoichiometric iron arsenide superconductor KFe$_2$As$_2$.
The crystals were characterized by residual resistivity ratio,
$\rho(300K)/\rho(0)$ up to 3000 and resistive transition midpoint temperature,
$T_c$=3.8 K, significantly higher than in previous studies on the same
material. We find increased $H_{c2}(T)$ for both directions of the magnetic
field, which scale with the increased $T_c$. This unusual linear $H_{c2}(T_c)$
scaling is not expected for orbital limiting mechanism of the upper critical
field in clean materials. | 1304.2689v1 |
2017-10-10 | Thermal conductivity and electrical resistivity of solid iron at Earth's core conditions from first-principles | We compute the thermal conductivity and electrical resistivity of solid hcp
Fe to pressures and temperatures of Earth's core. We find significant
contributions from electron-electron scattering, usually neglected at high
temperatures in transition metals. Our calculations show a quasi-linear
relation between electrical resistivity and temperature for hcp Fe at extreme
high pressures. We obtain thermal and electrical conductivities that are
consistent with experiments considering reasonable error. The predicted thermal
conductivity is reduced from previous estimates that neglect electron-electron
scattering. Our estimated thermal conductivity for the outer core is 77$\pm$10
W/m/K, and is consistent with a geodynamo driven by thermal convection. | 1710.03564v6 |
2014-08-20 | Carbon Memory Assessment | The geometrical and performance scaling of silicon CMOS integrated circuit
technology over the past 50 years has enabled many affordable new products for
business and consumer applications. Recognizing that Flash is approaching its
ultimate physical scaling limits within the next 10 years or so, the global
electronics research community has begun an intense search for a new paradigm
and technology for extending the functional scaling of memory technologies.
Several promising nonvolatile memory concepts have emerged, based on different
switching and retention mechanisms from those of Flash memory, e.g., STTRAM,
RRAM, PCM and more recently, resistive memories based on carbon, which are the
topic of this paper. This paper will introduce into the diverse field of carbon
materials by recollecting some effects in carbon that can be used to produce a
multiple time switchable, non-volatile unipolar resistive memory with potential
high scalability down to atomic dimensions. Carbon-based memory is a
non-volatile resistive memory, therefore, the same architectures, circuits,
select transistor or diodes like in ReRAM or PCRAM can be considered as
implementation. The big advantage of carbon memory might be the high
temperature retention of 250 C, which makes it attractive for automotive and
harsh conditions. This is a white paper for the ITRS meeting on emerging
research devices (ERD) in Albuquerque, New Mexico, on August 25-26, 2014. | 1408.4600v1 |
2003-11-06 | Violation of the Mott-Ioffe-Regel Limit: High-temperature Resistivity of Itinerant Magnets Srn+1RunO3n+1 (n=2,3,infinity) and CaRuO3 | Srn+1RunO3n+1 represents a class of layered materials whose physical
properties are a strong function of the number of Ru-O layers per unit cell, n.
This series includes the p-wave superconductor Sr2RuO4 (n=1), enhanced
paramagnetic Sr3Ru2O7 (n=2), nearly ferromagnetic Sr4Ru3O10 (n=3) and itinerant
ferromagnetic SrRuO3 (n=infinity). In spite of a wide spectrum of physical
phenomena, this series of materials along with paramagnetic CaRuO3 shares two
major characteristics, namely, robust Fermi liquid behavior at low temperatures
and anomalous transport behavior featured by linear temperature dependence of
resistivity at high temperature where electron wavepackets are no longer
clearly defined. There is no crossover separating such two fundamentally
different states. In this paper, we report results of our study that
systematically addresses anisotropy and temperature dependence of basal-plane
and c-axis resistivity as a function of n for the entire Srn+1RunO3n+1 series
and CaRuO3 and for a wide temperature range of 1.7 K<T<900 K. It is found that
the anomalous transport behavior correlates with magnetic susceptibility and
becomes stronger with decreasing dimensionality. Implications of these results
are discussed. | 0311142v1 |
2022-03-09 | Vanadium doped beta-Ga2O3 single crystals: Growth, Optical and Terahertz characterization | We report the growth of electrically-resistive vanadium-doped beta-Ga2O3
single crystals via the optical floating zone technique. By carefully
controlling the growth parameters V-doped crystals with very high electrical
resistivity compared to the usual n-type V-doped beta-Ga2O3 (ne~10^(18)/cm^3)
can be synthesized. The optical properties of such high resistive V-doped
b-Ga2O3 are significantly different compared to the undoped and n-doped
crystals. We study the polarization-dependent Raman spectra,
polarization-dependent transmission, temperature-dependent photoluminescence in
the optical wavelength range and the THz transmission properties in the 0.2 -
2.6 THz range. The V-doped insulating Ga2O3 crystals show strong birefringence
with refractive index contrast Dn of 0.3+-0.02 at 1 THz, suggesting it to be an
ideal material for optical applications in the THz region. | 2203.04941v1 |
2017-05-08 | Systematic efficiency study of line-doubled zone plates | Line-doubled Fresnel zone plates provide nanoscale, high aspect ratio
structures required for efficient high resolution imaging in the multi-keV
x-ray range. For the fabrication of such optics a high aspect ratio HSQ resist
template is produced by electron-beam lithography and then covered with Ir by
atomic layer deposition (ALD). | 1705.02807v1 |
2020-03-23 | Plasma Surface Metallurgy of Materials Based on Double Glow Discharge Phenomenon | Plasma Surface Metallurgy/Alloying is a kind of surface metallurgy/alloying
to employ low temperature plasma produced by glow discharge to diffuse alloying
elements into the surface of substrate material to form an alloy layer. The
first plasma surface metallurgy technology is plasma nitriding invented by
German scientist Dr. Bernard Berghuas in 1930. He was the first person to apply
glow discharge to realize the surface alloying. In order to break the
limitation of plasma nitriding technology, which can only be applied to a few
non-metallic gaseous elements such as nitrogen, carbon, sulfur, the "Double
Glow Discharge Phenomenon"was found in 1978. Based on this phenomenon the
"Double Glow Plasma Surface Metallurgy Technology", also known as the "Xu-Tec
Process" was invented in 1980. It can utilize any chemical elements in the
periodic table including solid metallic, gas non-metallic elements and their
combination to realize plasma surface alloying, hence greatly expanded the
field of surface alloying. Countless surface alloys with high hardness, wear
resistance and corrosion resistance, such as high speed steels, nickel base
alloys and burn resistant alloys have been produced on the surfaces of a
variety of materials. This technology may greatly improve the surface
properties of metal materials, comprehensively improve the quality of
mechanical products, save a lot of precious alloy elements for human beings.
Based on the plasma nitriding technology, the Xu-Tec Process has opened up a
new material engineering field of "Plasma Surface Metallurgy". This Review
Article briefly presents the history of glow discharge and surface alloying,
double glow discharge phenomenon, basic principle and current status of Double
Glow Plasma Surface Metallurgy/Alloying. Industrial applications, advantages
and future potential of the Xu-Tec process are also presented. | 2003.10250v1 |
2024-05-23 | Concurrence of directional Kondo transport and incommensurate magnetic order in the layered material AgCrSe$_2$ | In this work, we report on the concurrent emergence of the directional Kondo
behavior and incommensurate magnetic ordering in a layered material. We employ
temperature- and magnetic field-dependent resistivity measurements,
susceptibility measurements, and high resolution wavelength X-ray diffraction
spectroscopy to study the electronic properties of AgCrSe$_2$. Impurity Kondo
behavior with a characteristic temperature of $T_\text K$ = 32 K is identified
through quantitative analysis of the in-plane resistivity, substantiated by
magneto-transport measurements. The agreement between our experimental data and
the Schlottmann's scaling theory allows us to determine the impurity spin as
$S$ = 3/2. Furthermore, we discuss the origin of the Kondo behavior and its
relation to the material's antiferromagnetic transition. Our study uncovers an
unusual phenomenon -- the equivalence of the N\'eel temperature and the Kondo
temperature -- paving the way for further investigations into the intricate
interplay between impurity physics and magnetic phenomena in quantum materials,
with potential applications in advanced electronic and magnetic devices. | 2405.14541v1 |
2013-04-11 | Resistance switching in oxides with inhomogeneous conductivity | Electric-field-induced resistance switching (RS) phenomena have been studied
for over 60 years in metal/dielectrics/metal structures. In these experiments a
wide range of dielectrics have been studied including binary transition metal
oxides, perovskite oxides, chalcogenides, carbon- and silicon-based materials,
as well as organic materials. RS phenomena can be used to store information and
offer an attractive performance, which encompasses fast switching speeds, high
scalability, and the desirable compatibility with Si-based
complementary-metal-oxide-semiconductor fabrication. This is promising for
nonvolatile memory technology, i.e. resistance random access memory (RRAM).
However, a comprehensive understanding of the underlying mechanism is still
lacking. This impedes a faster product development as well as an accurate
assessment of the device performance potential. Generally speaking, RS occurs
not in the entire dielectric but only a small, confined region, which results
from the local variation of conductivity in dielectrics. In this review, we
focus on the RS in oxides with such an inhomogeneous conductivity. According to
the origin of the conductivity inhomogeneity, the RS phenomena and their
working mechanism are reviewed by dividing them into two aspects: interface RS,
based on the change of contact resistance at metal/oxide interface due to the
change of Schottky barrier and interface chemical layer, and bulk RS, realized
by the formation, connection, and disconnection of conductive channels in the
oxides. Finally the current challenges of RS investigation and the potential
improvement of the RS performance for the nonvolatile memories are discussed. | 1304.3290v1 |
2018-01-11 | Modeling the Oblique Spin Precession in Lateral Spin Valves for Accurate Determination of Spin Lifetime Anisotropy: Effect of Finite Contact Resistance and Channel Length | The spin lifetime anisotropy is an important quantity for investigating the
spin relaxation mechanisms in graphene and in heterostructures of
two-dimensional materials. We generalize the diffusive spin transport equations
of oblique spin precession in a lateral spin valve with finite contact
resistance. This yields a method to determine the spin lifetime anisotropy
ratio {\xi}={\tau}$_{\perp}$/{\tau}$_{\parallel}$, which is the ratio between
lifetimes of spin polarized perpendicular and parallel to the graphene surface.
By solving the steady-state Bloch equations, we show that the line-shape of the
oblique spin precession signal can be described with six dimensionless
parameters, which can be solved analytically. We demonstrate that the
anisotropic spin precession characteristics can be strongly suppressed by
contact induced spin relaxation originating from conductance mismatch between
the channel material and electrodes. To extract the spin lifetime anisotropy
ratio accurately, we develop a closed form equation that includes the effect of
finite contact resistance. Furthermore, we demonstrate that in the high contact
resistance regime, the minimum channel length required for accurately
determining the spin lifetime anisotropy for a sufficiently low external
magnetic field is only determined by the diffusion coefficient of the channel
material, as opposed to the spin diffusion length. Our work provides an
accurate model to extract the spin lifetime anisotropy ratio from the oblique
spin precession measurement, and can be used to guide the device design for
such measurements. | 1801.03606v1 |
2019-03-14 | Low Resistivity and High Breakdown Current Density of 10-nm Diameter van der Waals TaSe3 Nanowires by Chemical Vapor Deposition | Micron-scale single-crystal nanowires of metallic TaSe3, a material that
forms -Ta-Se3-Ta-Se3- stacks separated from one another by a tubular van der
Waals (vdW) gap, have been synthesized using chemical vapor deposition (CVD) on
a SiO2/Si substrate, in a process compatible with semiconductor industry
requirements. Their electrical resistivity was found unaffected by downscaling
from the bulk to as little as 7 nm in width and height, in striking contrast to
the resistivity of copper for the same dimensions. While the bulk resistivity
of TaSe3 is substantially higher than that of bulk copper, at the nanometer
scale the TaSe3 wires become competitive to similar-sized copper ones.
Moreover, we find that the vdW TaSe3 nanowires sustain current densities in
excess of 108 A/cm2 and feature an electromigration energy barrier twice that
of copper. The results highlight the promise of quasi-one-dimensional
transition metal trichalcogenides for electronic interconnect applications and
the potential of van der Waals materials for downscaled electronics. | 1903.06227v1 |
2019-09-01 | Low activation, refractory, high entropy alloys for nuclear applications | Two new, low activation high entropy alloys (HEAs) TiVZrTa and TiVCrTa are
studied for use as in-core, structural nuclear materials for in-core nuclear
applications. Low-activation is a desirable property for nuclear reactors, in
an attempt to reduce the amount of high level radioactive waste upon
decommissioning, and for consideration in fusion applications.The alloy TiVNbTa
is used as a starting composition to develop two new HEAs; TiVZrTa and TiVCrTa.
The new alloys exhibit comparable indentation hardness and modulus, to the
TiVNbTa alloy in the as-cast state. After heavy ion implantation the new alloys
show an increased irradiation resistance. | 1909.00373v1 |
2019-08-07 | Part I: Theoretical Predictions of Preferential Oxidation in Refractory High Entropy Materials | High entropy materials, which include high entropy alloys, carbides, and
borides, are a topic of substantial research interest due to the possibility of
a large number of new material compositions that could fill gaps in application
needs. There is a current need for materials exhibiting high temperature
stability, particularly oxidation resistance. A systematic understanding of the
oxidation behavior in high entropy materials is therefore required. Prior work
notes large differences in the thermodynamic favorability between oxides formed
upon oxidation of high entropy materials. This work uses both analytical and
computational thermodynamic approaches to investigate and quantify the effects
of this large variation and the resulting potential for preferential component
oxidation in refractory high entropy materials including group IV-, V- and
VI-element based alloys and ceramics. Thermodynamic calculations show that a
large tendency towards preferential oxidation is expected in these materials,
even for elements whose oxides exhibit a small difference in thermodynamic
favorability. The effect is reduced in carbides, compared to their alloy
counterparts. Further, preferential oxidation in high entropy refractory
materials could result in possible destabilization of the solid solution or
formation of other, competing phases, with corresponding changes in bulk
material properties. | 1908.02654v2 |
2011-03-30 | The efficient spin injector scheme based on Heusler materials | We present the rational design scheme intended to provide the stable high
spin-polarization at the interfaces of the magneto-resistive junctions by
fulfilling the criteria of structural and chemical compatibilities at the
interface. This can be realized by joining the semiconducting and half-metallic
Heusler materials with similar structures. The present first-principal
calculations verify that interface remains half-metallic if the nearest
interface layers effectively form a stable Heusler material with the properties
intermediate between the surrounding bulk parts. This leads to a simple rule
for selecting the proper combinations. | 1103.5928v1 |