Browse
Submit Data
Databases
API
Help

Dataset Information

20 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Tunable resistivity of correlated VO₂(A) and VO₂(B) via tungsten doping.

ABSTRACT: Applications of correlated vanadium dioxides VO₂(A) and VO₂(B) in electrical devices are limited due to the lack of effective methods for tuning their fundamental properties. We find that the resistivity of VO₂(A) and VO₂(B) is widely tunable by doping them with tungsten ions. When x < 0.1 in V_1-xW_xO₂(A), the resistivity decreases drastically by four orders of magnitude with increasing x, while that of V_1-xW_xO₂(B) shows the opposite behaviour. Using spectroscopic ellipsometry and X-ray photoemission spectroscopy, we propose that correlation effects are modulated by either chemical-strain-induced redistribution of V-V distances or electron-doping-induced band filling in V_1-xW_xO₂(A), while electron scattering induced by disorder plays a more dominant role in V_1-xW_xO₂(B). The tunable resistivity makes correlated VO₂(A) and VO₂(B) appealing for next-generation electronic devices.

SUBMITTER: Choi S

PROVIDER: S-EPMC7297976 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Unraveling metal-insulator transition mechanism of VO₂ triggered by tungsten doping.

Project description:Understanding the mechanism of W-doping induced reduction of critical temperature (T(C)) for VO(2) metal-insulator transition (MIT) is crucial for both fundamental study and technological application. Here, using synchrotron radiation X-ray absorption spectroscopy combined with first-principles calculations, we unveil the atomic structure evolutions of W dopant and its role in tailoring the T(C) of VO(2) MIT. We find that the local structure around W atom is intrinsically symmetric with a tetragonal-like structure, exhibiting a concentration-dependent evolution involving the initial distortion, further repulsion, and final stabilization due to the strong interaction between doped W atoms and VO(2) lattices across the MIT. These results directly give the experimental evidence that the symmetric W core drives the detwisting of the nearby asymmetric monoclinic VO(2) lattice to form rutile-like VO(2) nuclei, and the propagations of these W-encampassed nuclei through the matrix lower the thermal energy barrier for phase transition.

| S-EPMC3381290 | biostudies-other

Van der Waals MoS2/VO2 heterostructure junction with tunable rectifier behavior and efficient photoresponse.

Project description:Junctions between n-type semiconductors of different electron affinity show rectification if the junction is abrupt enough. With the advent of 2D materials, we are able to realize thin van der Waals (vdW) heterostructures based on a large diversity of materials. In parallel, strongly correlated functional oxides have emerged, having the ability to show reversible insulator-to-metal (IMT) phase transition by collapsing their electronic bandgap under a certain external stimulus. Here, we report for the first time the electronic and optoelectronic characterization of ultra-thin n-n heterojunctions fabricated using deterministic assembly of multilayer molybdenum disulphide (MoS2) on a phase transition material, vanadium dioxide (VO2). The vdW MoS2/VO2 heterojunction combines the excellent blocking capability of an n-n junction with a high conductivity in on-state, and it can be turned into a Schottky rectifier at high applied voltage or at temperatures higher than 68 °C, exploiting the metal state of VO2. We report tunable diode-like current rectification with a good diode ideality factor of 1.75 and excellent conductance swing of 120 mV/dec. Finally, we demonstrate unique tunable photosensitivity and excellent junction photoresponse in the 500/650 nm wavelength range.

| S-EPMC5660225 | biostudies-literature

Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate.

Project description:A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He-Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates. Then, bottom-contact graphene field effect transistors (G-FETs) were fabricated on the NP SiO2/Si substrate to measure the transfer curves. The graphene transferred onto the NP SiO2/Si substrate showed relatively n-doped behavior compared to the graphene transferred onto a flat SiO2/Si substrate, as evidenced by the blue-shift of the 2D peak position (∼2700 cm-1) in the Raman spectra due to contact doping. As the porosity increased within the substrate, the Dirac voltage shifted to a more positive or negative value, depending on the initial doping type (p- or n-type, respectively) of the contact doping. The Dirac voltage shifts with porosity were ascribed mainly to the compensation for the reduced capacitance owing to the SiO2-air hetero-structured dielectric layer within the periodically aligned nanopores capped by the suspended graphene (electrostatic doping). The hysteresis (Dirac voltage difference during the forward and backward scans) was reduced when utilizing an NP SiO2/Si substrate with smaller pores and/or a low porosity because fewer H2O or O2 molecules could be trapped inside the smaller pores.

| S-EPMC9078577 | biostudies-literature

Crystallographic anisotropy of the resistivity size effect in single crystal tungsten nanowires.

Project description:This work demonstrates an anisotropic increase in resistivity with decreasing width in single crystal tungsten (W) nanowires having a height of 21 nm. Nanowire-widths were in the range of 15-451 nm, with the anisotropy observed for widths below 50 nm. The longitudinal directions of the nanowires coincided with the <100>, <110> and <111> orientations of the body centered cubic phase of W. The resistivity increase was observed to be minimized for the <111>-oriented single crystal nanowires, exhibiting a factor of two lower increase in resistivity at a width of ~15 nm, relative to the thin film resistivity (i.e., an infinitely wide wire). The observed anisotropy is attributed to crystallographic anisotropy of the Fermi velocity and the resultant anisotropy of the electron mean free path in W, and underscores the critical role of crystallographic orientation in nanoscale metallic conduction.

| S-EPMC3763248 | biostudies-literature

Controllable Doping Characteristics for WSxSey Monolayers Based on the Tunable S/Se Ratio.

Project description:Transition metal dichalcogenides (TMDs) have attracted much attention because of their unique characteristics and potential applications in electronic devices. Recent reports have successfully demonstrated the growth of 2-dimensional MoSxSey, MoxWyS2, MoxWySe2, and WSxSey monolayers that exhibit tunable band gap energies. However, few works have examined the doping behavior of those 2D monolayers. This study synthesizes WSxSey monolayers using the CVD process, in which different heating temperatures are applied to sulfur powders to control the ratio of S to Se in WSxSey. Increasing the Se component in WSxSey monolayers produced an apparent electronic state transformation from p-type to n-type, recorded through energy band diagrams. Simultaneously, p-type characteristics gradually became clear as the S component was enhanced in WSxSey monolayers. In addition, Raman spectra showed a red shift of the WS2-related peaks, indicating n-doping behavior in the WSxSey monolayers. In contrast, with the increase of the sulfur component, the blue shift of the WSe2-related peaks in the Raman spectra involved the p-doping behavior of WSxSey monolayers. In addition, the optical band gap of the as-grown WSxSey monolayers from 1.97 eV to 1.61 eV is precisely tunable via the different chalcogenide heating temperatures. The results regarding the doping characteristics of WSxSey monolayers provide more options in electronic and optical design.

| S-EPMC10385163 | biostudies-literature

Tunable resistivity exponents in the metallic phase of epitaxial nickelates.

Project description:We report a detailed analysis of the electrical resistivity exponent of thin films of NdNiO3 as a function of epitaxial strain. Thin films under low strain conditions show a linear dependence of the resistivity versus temperature, consistent with a classical Fermi gas ruled by electron-phonon interactions. In addition, the apparent temperature exponent, n, can be tuned with the epitaxial strain between n = 1 and n = 3. We discuss the critical role played by quenched random disorder in the value of n. Our work shows that the assignment of Fermi/Non-Fermi liquid behaviour based on experimentally obtained resistivity exponents requires an in-depth analysis of the degree of disorder in the material.

| S-EPMC7289814 | biostudies-literature

Abnormal drop in electrical resistivity with impurity doping of single-crystal Ag.

Project description:Resistivity is an intrinsic feature that specifies the electrical properties of a material and depends on electron-phonon scattering near room temperature. Reducing the resistivity of a metal to its potentially lowest value requires eliminating grain boundaries and impurities, but to date few studies have focused on reducing the intrinsic resistivity of a pure metal itself. We could reduce the intrinsic resistivity of single-crystal Ag, which has an almost perfect structure, by impurity doping it with Cu. This paper presents our results: resistivity was reduced to 1.35 μΩ · cm at room temperature after 3 mol% Cu-doping of single-crystal Ag. Various mechanisms were examined in an attempt to explain the abnormal behavior.

| S-EPMC4071311 | biostudies-literature

Coexistent VO2 (M) and VO2 (B) Polymorphous Thin Films with Multiphase-Driven Insulator-Metal Transition.

Project description:Reversible insulator-metal transition (IMT) and structure phase change in vanadium dioxide (VO2) remain vital and challenging with complex polymorphs. It is always essential to understand the polymorphs that coexist in desired VO2 materials and their IMT behaviors. Different electrical properties and lattice alignments in VO2 (M) and VO2 (B) phases have enabled the creation of versatile functional devices. Here, we present polymorphous VO2 thin films with coexistent VO2 (M) and VO2 (B) phases and phase-dependent IMT behaviors. The presence of VO2 (B) phases may induce lattice distortions in VO2 (M). The plane spacing of (011)M in the VO2 (M) phase becomes widened, and the V-V and V-O vibrations shift when more VO2 (B) phase exists in the VO2 (M) matrix. Significantly, the coexisting VO2 (B) phases promote the IMT temperature of the polymorphous VO2 thin films. We expect that such coexistent polymorphs and IMT variations would help us to understand the microstructures and IMT in the desired VO2 materials and contribute to advanced electronic transistors and optoelectronic devices.

| S-EPMC10180398 | biostudies-literature

Selective Doping to Controllably Tailor Maximum Unit-Cell-Volume Change of Intercalating Li+ -Storage Materials: A Case Study of γ Phase Li3 VO4.

Project description:Capacity decay of an intercalating Li+ -storage material is mainly due to the its particle microcracks from stress-causing volume change. To extend its cycle life, its unit-cell-volume change has to be minimized as much as possible. Here, based on a γ-Li3 VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit-cell-volume change, then clarify the relationship between its crystal-structure openness and maximum unit-cell-volume change, and finally demonstrate the superiority of "zero-strain" materials within 25-60 °C (especially at 60 °C). With increasing the large-sized Ge4+ dopant, the unit-cell volume of γ-Li3+ x Gex V1- x O4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit-cell-volume change. In contrast, the doping with small-sized Si4+ shows a reverse trend. The tailoring reveals that γ-Li3.09 Ge0.09 V0.91 O4 owns the smallest maximum unit-cell-volume change of 0.016% in the research field of intercalating Li+ -storage materials. Consequently, γ-Li3.09 Ge0.09 V0.91 O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity-retention percentages after 1800/1500 cycles at 2 A g-1 . This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long-life lithium-ion batteries.

| S-EPMC9405516 | biostudies-literature

Surface group-modified MXene nano-flake doping of monolayer tungsten disulfides.

Project description:Exciton/trion-involved optoelectronic properties have attracted exponential amount of attention for various applications ranging from optoelectronics, valleytronics to electronics. Herein, we report a new chemical (MXene) doping strategy to modulate the negative trion and neutral exciton for achieving high photoluminescence yield of atomically thin transition metal dichalcogenides, enabled by the regulation of carrier densities to promote electron-bound trion-to-exciton transition via charge transfer from TMDCs to MXene. As a proof of concept, the MXene nano-flake-doped tungsten disulfide is demonstrated to obtain an enhanced PL efficiency of up to ∼five folds, which obviously exceeds the reported efficiency upon electrical and/or plasma doping strategies. The PL enhancement degree can also be modulated by tuning the corresponding surface functional groups of MXene nano-flakes, reflecting that the electron-withdrawing functional groups play a vital role in this charge transfer process. These findings offer promising clues to control the optoelectronic properties of TMDCs and expand the scope of the application of MXene nano-flakes, suggesting a possibility to construct a new heterostructure junction based on MXenes and TMDCs.

| S-EPMC9417804 | biostudies-literature