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Electrical triggering of a metal-insulator transition (MIT) often results in the formation of characteristic spatial patterns such as a metallic filament percolating through an insulating matrix or an insulating barrier splitting a conducting matrix. When MIT triggering is driven by electrothermal effects, the temperature of the filament or barrier can be substantially higher than the rest of the material. Using X-ray microdiffraction and dark-field X-ray microscopy, we show that electrothermal MIT triggering leads to the development of an inhomogeneous strain profile across the switching device, even when the material does not undergo a pronounced, discontinuous structural transition coinciding with the MIT. Diffraction measurements further reveal evidence of unique features associated with MIT triggering including lattice distortions, tilting, and twinning, which indicate structural nonuniformity of both low- and high-resistance regions inside the switching device. Such lattice deformations do not occur under equilibrium, zero-voltage conditions, highlighting the qualitative difference between states achieved through increasing temperature and applying voltage in nonlinear electrothermal materials. Electrically induced strain, lattice distortions, and twinning could have important contributions in the MIT triggering process and drive the material into nonequilibrium states, providing an unconventional pathway to explore the phase space in strongly correlated electronic systems.

In this study, nitrogen (N) is doped into VO2 thin films through mist chemical vapor deposition (CVD), and the effect of the doping on metal–insulator transition (MIT) temperatures is investigated. The N‐doped VO2 thin films are grown on an SnO2 buffer layer. The N‐doped VO2 lattice spacing tends to expand as the growth temperature decreased, which indicates that the incorporation of N into the lattice is derived from the Ethylenediamine. Secondary ion mass spectrometry (SIMS) is conducted to investigate the relationship between the decrease in the transition temperature and N concentration. The results reveal that the sample grown at 425 °C contains approximately 2 × 1020 cm−3 of N. Thus, efficient nitrogen doping can be achieved through mist CVD. The temperature‐resistance characteristics of VO2 thin films are measured to investigate their electrical properties and MIT temperatures. The results reveal that for undoped samples, the transition temperature slightly decreases with the decrease in the growth temperature. Furthermore, the sample grown at 425 °C exhibits a considerable change in resistance because of MIT at approximately 29.5 °C. These results prove the potential of using mist CVD N‐doped thin films for smart window applications to address future energy problems. [ABSTRACT FROM AUTHOR]

It is known that the insulator-metal transition occurs upon loading guest Na atoms into cages of the zeolite low silica X (LSX). In this study, the metallic and insulating phases of this material were investigated by the muon spin rotation (μ SR) method. We succeeded in detecting the muon frequency shift K μ for the insulating and metallic phases in low temperatures, which was not observed in the previous 23 Na-NMR measurements. Contribution to K μ , which is proportional to the density of state at the Fermi energy, is deduced to be 18±2% of that in the bulk metallic Na. [ABSTRACT FROM AUTHOR]

Gate‐controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non‐layered materials. The non‐layered rhombohedral Cr2S3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS2 and 0D Cr1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined‐standing grown 2D Cr2S3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all‐dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr1/3 layers, as revealed by cross‐sectional scanning transmission electron microscope, permitting the insertion of Li+ ions. An unprecedented metal‐insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr2S3‐based ionic field‐effect transistors. Theoretical calculations corroborate the metallization induced by Li‐ion intercalation. This work sheds light on the understanding of growth mechanism, structure‐property correlation and highlights the diverse potential applications of 2D non‐layered Cr2S3 superlattice. [ABSTRACT FROM AUTHOR]

Characteristics of VO2 films prepared on alkali-free glass substrates by chemical solution deposition (CSD) using vanadyl oxalate nhydrate as the raw material are investigated. Diffraction peaks corresponding to VO2 are observed in the samples obtained at firing temperatures of 350 to 550°C. However, diffraction peaks of the samples obtained at 500 and 550°C show a mixture of VO2 and V6O13 phases. Regarding the surface and cross-section morphology of the films, the crystal grain size and porosity of the films steadily increase with firing temperature. The samples show an abrupt change in resistivity around 70°C. The change in resistivity caused by the metal-insulator transition are about three orders of magnitude. The sample transmittance in the near-infrared region decreases sharply with the phase transition. The maximum reduction in transmittance at 2000nm is 55.4%. [ABSTRACT FROM AUTHOR]

The electrical and magnetic properties of strongly correlated manganese oxides originate from and depend on the coupling of spin, orbital, lattice and other degrees of freedom, and can also be controlled by external stimuli (such as a magnetic field). Here, the films have been prepared using spin-coating method to determine the role of Jahn–Teller (JT) distortion and double exchange (DE) interaction in electronic transport and magnetoresistance (MR) by magnetic field in La 0. 7 − x SmxCa 0. 3 MnO3/SrTiO3(001). The Sm-induced lattice distortion suppresses the metal-insulator transition temperature and increases the films' resistivity, which is due to the weakening of the DE interaction between Mn 3 + –O 2 − –Mn 4 + ions and the enhancement of the single electron bandwidth. Moreover, the MR can be increased to 96.5% and the AMR can be increased to 66.6% under 1 T magnetic field. These findings indicate the importance of JT distortion in multi-field control of hole-doped perovskite manganites. [ABSTRACT FROM AUTHOR]

High temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs) have garnered significant attention due to their expanded range of hydrogen sources and simplified management systems. However, the frequent start‐up and shut‐down (SU/SD) caused fuel starvation operation condition seriously deteriorates the performance and lifetime of the fuel cell. In this manuscript, VO2 was incorporated in the anode to restrain fuel starvation of the electrode. Under the operation condition, the insulative VO2 would reversibly transform into metallic HxVO2 by intercalating hydrogen, and HxVO2 can automatically release hydrogen, which could act as the hydrogen buffer and suppress reverse‐current degradation. After the hydrogen release, the generated insulating VO2 would prevent the side reactions during fuel starvation. Compared to the traditional Pt anode, the electrode with VO2 showed much higher output power and greatly improved durability after fuel starvation. This work demonstrates the in situ reversible hydrogen storage/release‐controlled metal‐insulator phase transition strategy to enhance the durability of fuel cells. [ABSTRACT FROM AUTHOR]

Neuromorphic computing offers significant advantages in addressing data redundancy and enhancing system energy efficiency. Although extensive research has been conducted on pulsed neural networks and bionic sensors, the development of artificial electronic afferent neurons for low-energy information transfer remains limited. This study introduces an artificial afferent neuron comprising a vanadium dioxide (VO2) device, capacitor and resistor. The VO2 devices exhibit stable electrically induced metal-insulator transition (MIT). Leveraging the MIT of this device, we develop an artificial afferent neuron to transform constant or sinusoidal analog signals into pulsed voltage signals. The output frequency increases with the increase of the input voltage, mimicking the faster pulse outputs of biological afferent neurons in response to stronger stimuli. [ABSTRACT FROM AUTHOR]

Herein, in order to successfully create high-density La 0.67 Ca 0.33- x Sr x MnO 3 : Ag 0.15 (LCSMO: Ag) ceramics (0 ≤ x ≤ 0.05), this research combines sol-gel and solid-phase processes. LCSMO: Ag ceramics electrical transport and magnetic properties were thoroughly investigated. XRD verified that the high-purity orthorhombic perovskite structure (space group Pnma) was produced. As Sr doping rises, the grain size grows, the single electron bandwidth increases, the metal-insulator transition temperature (T MI) continues to climb, and temperature coefficient of resistance (TCR) and magnetoresistance (MR) steadily drop. When x = 0.04, the T MI reaches 302.2 K. At this time, the TCR peak (TCR peak) reaches 24.0 %·K−1 and the MR peak reaches 49.2 %. These results demonstrate that Sr may effectively raise the T MI of LCMO: Ag ceramics to room temperature while maintaining high TCR and MR Values, which benefits the material's potential applications in devices such as uncooled infrared detectors. [ABSTRACT FROM AUTHOR]

The transport properties of the perovskites BaPb1 − xSnxO3 (0 ≤ x ≤ 0.4, and x = 1), synthesized for the first time, are investigated in the range (300 –4.2 K). They were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and FTIR-ATR spectroscopy. The weak thermal dependence of conductivity on temperature is characteristic of degenerate behavior with a finite density of states at the Fermi level. The linear behavior indicates a thermally activated mobility (= 4.8 × 10− 6 cm2 V− 1 s− 1) while the negative sign of the thermo-power, indicates that the mobile carriers are electrons, due to non-stoichiometry of oxygen. The band overlapping O2−: 2p-Pb: 6s is involved in the semi-metal BaPbO3. The magnetic susceptibility exhibits a Pauli-type paramagnetism due to itinerant electrons. A pronounced dip, associated with a phonon drag contribution is observed near 25 K. The non-linear dependence of log σ vs. T− 1 at low temperatures results from a variable range hopping evidenced by the plot log σ vs. T− 0.25. The metal-non-metal transition is of Anderson type due to random potential introduced by substituting Pb4+ with Sn4+. The capacitance− 2 potential (C− 2 - E) plots show linear behaviors from which flat band potentials are determined (-0.22 - -0.83 VSCE). The Electrochemical Impedance Spectroscopy exhibits semicircles assigned to the capacitive behavior with a low density of surface states within the gap region. [ABSTRACT FROM AUTHOR]

The effect of sintering temperature on the structural, magnetic, and dielectric properties of NiCr2O4 ceramics was investigated. A powder X-ray analysis indicates that the prepared nanocrystallites effectively inhibit the cooperative Jahn–Teller distortion, thereby stabilizing the high-temperature cubic phase structure with space group Fd-3m. Multiple transitions are confirmed by temperature-dependent magnetization M(T) data. Moreover, the magnetization value decreases and the Curie temperature increases with a decrease in the crystallite size. The low-temperature-dependent real permittivity (ε′-T) for a NiCr2O4 crystallite size of 78 nm exhibits a broad maximum at 40 K that is independent of frequency. This establishes a correlation between electric ordering and the underlying magnetic structure. The temperature dependency of the dielectric constant at fixed frequencies for both NiCr2O4 crystallite sizes rises with temperature for a certain range of frequencies. A significant improvement is evident: the dielectric constant (ε') at room temperature reaches approximately 5738 for the sample with 28 nm crystallites, while the 78 nm crystallite sample shows a noticeable drop to ε'~174. The frequency-dependent conductivity curves for both types of NiCr2O4 nanocrystallites have different conductivity values. The lower-crystallite-size sample demonstrates higher conductivity values than the 78 nm crystallite size one. This observation is attributed to the decrease in crystallite size, which increases the number of grain boundaries and, consequently, scatters a higher number of charge carriers. [ABSTRACT FROM AUTHOR]

We use a combination of density functional theory (DFT) and dynamical mean field theory (DMFT) to unveil orbital field-induced electronic structure reconstruction of the atomic Sn layer deposited onto a Si(111) surface (Sn/Si(111)− 3 × 3 R 30 ∘ ), also referred to as α -Sn. Our DFT + DMFT results indicate that α -Sn is an ideal testing ground to explore electric field-driven orbital selectivity and Mott memory behavior, all arising from the close proximity of α -Sn to metal insulator transitions. We discuss the relevance of orbital phase changes for α -Sn in the context of the current–voltage ( I − V ) characteristic for future silicon-based metal semiconductor atomristors. [ABSTRACT FROM AUTHOR]

Abstract In this study, nitrogen (N) is doped into VO2 thin films through mist chemical vapor deposition (CVD), and the effect of the doping on metal–insulator transition (MIT) temperatures is investigated. The N‐doped VO2 thin films are grown on an SnO2 buffer layer. The N‐doped VO2 lattice spacing tends to expand as the growth temperature decreased, which indicates that the incorporation of N into the lattice is derived from the Ethylenediamine. Secondary ion mass spectrometry (SIMS) is conducted to investigate the relationship between the decrease in the transition temperature and N concentration. The results reveal that the sample grown at 425 °C contains approximately 2 × 1020 cm−3 of N. Thus, efficient nitrogen doping can be achieved through mist CVD. The temperature‐resistance characteristics of VO2 thin films are measured to investigate their electrical properties and MIT temperatures. The results reveal that for undoped samples, the transition temperature slightly decreases with the decrease in the growth temperature. Furthermore, the sample grown at 425 °C exhibits a considerable change in resistance because of MIT at approximately 29.5 °C. These results prove the potential of using mist CVD N‐doped thin films for smart window applications to address future energy problems.

Vanadium dioxide (VO2) undergoes a reversible first‐order metal‐to‐insulator transition (MIT) from a high‐temperature metallic phase to a low‐temperature insulating phase at a critical temperature Tc of 68°C. The MIT is accompanied by a structural phase transition. In addition to the metallic high‐temperature rutile phase, several insulating phases may be involved depending on doping, interfacial stress, or external stimuli. Unambiguously identifying the crystal phases involved in the phase transition is of key interest from the point of view of application as well as fundamental science. We study the impact of Ti doping of VO2 thin films on (110) rutile TiO2 substrates. We conduct a careful analysis of structural properties by combining results of x‐ray diffraction, Raman spectroscopy, and transmission electron microscopy. The transition temperature Tc of the deposited thin films decreases with increasing Ti‐content. All our thin film samples undergo a structural phase transition from the monoclinic M1‐phase to the rutile R‐phase with increasing temperature without passing the intermediate monoclinic M2‐phase. A careful analysis of polarization and angle‐dependent Raman data reveals that, above Tc, the unit cell of the high‐temperature rutile TixV1‐xO2 phase is aligned with that of the rutile TiO2 substrate whereas, below Tc, 180°‐domains of the M1‐phase of TixV1‐xO2 are observed. The structural relationship between TiO2 substrate and the high respective low‐temperature phase of the TixV1‐xO2 determined by Raman spectroscopy is in excellent agreement with TEM results on these samples. Raman spectroscopy is a powerful tool for studying structural changes of VO2‐based samples in the vicinity of MIT. [ABSTRACT FROM AUTHOR]

In this work, we presented our results on the electrical and magnetoresistance characteristics of La0.7Ca0.1Pb0.2Mn1-2xAlxSnxO3 (x equal to 0 and 0.025) prepared using the sol–gel method. X-ray diffraction (XRD) analysis revealed that all samples crystallize in Rhombohedral structure with R-3c space group. In addition, to obtain further information regarding the electrical properties, we performed resistance versus temperature ρ (T) measurements under different applied magnetic fields using a standard four-probe technique. The resistivity data, represented as ρ (μ0H, T), indicated the presence of a transition from metal to semiconductor state. As the magnetic field increases, the maximum resistivity values decrease, and the temperature (TM-SC) at which the transition from insulator to metal occurs rises. In the temperature range where T is less than TM–SC, the electrical resistivity ρ (T) was modeled as ρ(T) = ρ0 + ρ2T2 + ρ4.5T4.5, signifying that the transport behavior is influenced by a combination of interactions involving electron–magnon, electron–phonon and electron–electron scattering processes. Conversely, in the temperature range exceeding TM–SC, the transport mechanism was elucidated through the utilization of adiabatic small polaron hopping and variable-range hopping models. To improve understanding of the variations in the resistivity profile across the temperature range, ρ (T) was fitted using the percolation model. Additionally, research was conducted on the magnetoresistance effect (MR %). The highest magnetoresistance values are observed around the temperature TM–SC. Highlights: La0.7Ca0.1Pb0.2Mn1-2xAlxSnxO3 was synthesized using the sol–gel method. X-ray diffraction (XRD) analysis confirmed that all samples crystallize in a Rhombohedral structure with an R-3c space group. The resistivity data, denoted as ρ (μ0H, T), showed a transition from a metallic to a semiconducting state. For temperatures below TM–SC, the electrical resistivity ρ (T) was described by the equation ρ(T) = ρ0 + ρ2T2 + ρ4.5T4.5, indicating that the transport properties are influenced by electron–magnon, electron–phonon, and electron–electron scattering processes. For temperatures above TM–SC, the transport mechanism was explained using adiabatic small polaron hopping and variable-range hopping models. Near the critical temperature, the resistivity was modeled using the percolation model. The highest magnetoresistance values were observed around the temperature TM–SC. [ABSTRACT FROM AUTHOR]

Analog neuromorphic circuits use a range of volatile and non-volatile memristive effects to mimic the functionalities of neurons and synapses. Creating devices with combined effects is important for reducing the footprint and power consumption of neuromorphic circuits. This work presents an epitaxial SmNiO3/BaTiO3 electrical device that displays non-volatile memristive switching to either allow or block access to a volatile threshold switching regime. This behavior arises from coupling the BaTiO3 ferroelectric polarization to SmNiO3 metal-insulator transition; the polarization in the BaTiO3 layer that is in contact with the SmNiO3 layer modifies the device resistance continuously in a controllable, non-volatile manner. Additionally, the polarization state varies the threshold voltage at which the Joule-heating-driven insulator-to-metal phase transition occurs in the nickelate, which results in a negative differential resistance curve and produces a sharp, volatile threshold switch. Reliable current oscillations with stable frequencies, large amplitude, and a relatively low driving voltage are demonstrated when the device is placed in a Pearson-Ansonlike circuit. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2) nanocrystalline materials are of great interest as for modern electronics and photonics as well as for energy saving technologies. Nevertheless, there still remains a challenge to realize their controllable synthesis, as evidenced by the low rate of implantation of existing technologies into mass production. Here, a hydrothermal reaction in a water-ethylene glycol (EG) solution has been coupled with the post-deposition annealing, yielding a range of phase-pure vanadium dioxide nanostructures on single-crystal r-sapphire substrate. A directed change in the viscosity of the precursor solution by using a change in the EG : H 2 O ratio makes it possible to control the nucleation rate and thus form VO 2 isolated nanocrystals, as well as their ordered ensembles with regular distribution and uniform films on the substrate. The obtained nanostructures were extensively characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. Continuous VO 2 nanostructures demonstrated a metal-insulator transition (MIT) with a jump in resistivity of about 103–104, as well as a giant terahertz (THz) modulation depth up to 86 % (in the range from 0.3 to 2.0 THz), which confirms their high-quality and the possibility of their use in the creation of functional electronic and THz optical devices. [ABSTRACT FROM AUTHOR]

We investigated the magnetic and electric properties of nanometer-sized vanadium dioxide (VO2) particles. VO2 nanoparticles were formed by milling VO2 powder. We measured the magnetic field dependence of the magnetization of the VO2 powder and nanoparticles. The VO2 powder did not exhibit ferromagnetism, whereas the VO2 nanoparticles exhibited ferromagnetism. In addition, we fabricated samples by bridging between electrodes with the VO2 nanoparticles, and the temperature dependence of their resistance was measured. Metal-insulator transitions (MITs) were observed, and the temperature range where the MIT occurred was wider than that in a typical bulk VO2. The VO2 nanoparticles exhibited these properties of ferromagnetism and MIT possibly because of the surface and size effects of the VO2 nanoparticles. These results indicate the first observation of the competitive coexistence of ferromagnetism and MIT of VO2 nanoparticles. [ABSTRACT FROM AUTHOR]

The effect of sintering temperature on the structural, magnetic, and dielectric properties of NiCr2O4 ceramics was investigated. A powder X-ray analysis indicates that the prepared nanocrystallites effectively inhibit the cooperative Jahn–Teller distortion, thereby stabilizing the high-temperature cubic phase structure with space group Fd-3m. Multiple transitions are confirmed by temperature-dependent magnetization M(T) data. Moreover, the magnetization value decreases and the Curie temperature increases with a decrease in the crystallite size. The low-temperature-dependent real permittivity (ε′-T) for a NiCr2O4 crystallite size of 78 nm exhibits a broad maximum at 40 K that is independent of frequency. This establishes a correlation between electric ordering and the underlying magnetic structure. The temperature dependency of the dielectric constant at fixed frequencies for both NiCr2O4 crystallite sizes rises with temperature for a certain range of frequencies. A significant improvement is evident: the dielectric constant (ε’) at room temperature reaches approximately 5738 for the sample with 28 nm crystallites, while the 78 nm crystallite sample shows a noticeable drop to ε’~174. The frequency-dependent conductivity curves for both types of NiCr2O4 nanocrystallites have different conductivity values. The lower-crystallite-size sample demonstrates higher conductivity values than the 78 nm crystallite size one. This observation is attributed to the decrease in crystallite size, which increases the number of grain boundaries and, consequently, scatters a higher number of charge carriers.

This research paper focuses on investigating the metal-insulator transition occurring in quasi-one-dimensional organic crystals of TTT(TCNQ)2. The study utilizes a 3D approximation approach and introduces a physical model that incorporates two essential electron-phonon interactions. The first interaction is akin to the deformation potential, while the second interaction follows a polaron type behavior. By employing the random phase approximation, the renormalized phonon spectrum is calculated across different temperatures and various values of the dimensionless Fermi momentum kF. The findings indicate that the transition exhibits characteristics of the Peierls type, and the critical temperature associated with the Peierls transition is determined. Furthermore, an interesting observation is made that the Peierls critical temperature experiences a notable decrease with an increase in carrier concentration.

The metal–insulator transition (MIT) observed in vanadium dioxide has been a topic of great research interest for past decades, with the underlying physics yet not fully understood due to the complex electron interactions and structures involved. The ability to understand and tune the MIT behavior is of vital importance from the perspective of both underlying fundamental science as well as potential applications. In this work, scanning transmission electron microscopy (STEM) is used to investigate cross‐section lamella of the VO2 films deposited using pulsed laser deposition on three substrates: c‐cut sapphire, TiO2(101) and TiO2(001). Advanced STEM imaging is performed in which also the oxygen atom columns are resolved. The overall film quality and structures on atomic and nanoscale are linked to the electrical transition characteristics. Relatively poor MIT characteristics are observed on c‐sapphire due to the presence of very small domains with six orientation variants, and on TiO2 (001) due to the presence of cracks induced by stress relaxation. However, the MIT on TiO2 (101) behaves favorably, despite similar stress relaxation which, however, only leads to domain boundaries but no cracks. [ABSTRACT FROM AUTHOR]

Thermal stealth and camouflage technologies have been developed to blend objects with surroundings to counter infrared detection, and the emissivity modulation engineering for this purpose is more effective than the temperature control alone. Vanadium oxide (VO 2) had abrupt changes of infrared (IR) transmission and IR emissivity across the metal-insulator transition at the temperature (T c) of 68 °C. However, relatively high T c and wide temperature hysteresis range, moderate IR emissivity modulation, and weak antioxidant ability for VO 2 limited its practical applications. Herein, we reported a method for the synthesis of W/Al co-doped VO 2 powders by sol-gel method combining with post-annealing, and then VO 2 based thin films were obtained by vacuum filtration process. These results showed that W/Al co-doping successfully reduced the T c and temperature hysteresis range to 43.8 °C and 7.5 °C, respectively. In addition, the IR emissivity decreased from 0.99 (room temperature) to 0.51 (90 °C) for W/Al co-doped VO 2 films, and the emissivity modulation was effectively improved. Furthermore, the antioxidant ability of as-prepared VO 2 nanoparticles was enhanced obviously by Al doping due to the generation of inert Al 2 O 3 on its surface. Therefore, this work provided a novel route for preparing VO 2 based infrared stealth materials which can be applied in infrared camouflage, sensors and smart windows. [ABSTRACT FROM AUTHOR]

Using first principle calculations, we study the structural, electric and magnetic properties of SrRu1−xZrxO3 (0 ≤ x ≤ 1). The spin-polarization calculations present that SrRu1−xZrxO3 is a ferromagnetic metal at x = 0, a ferromagnetic semiconductor at x = 0.125, 0.25, an antiferromagnetic semiconductor at x = 0.5 and a nonmagnetic insulator at x = 1, which is in agreement with available experiments. As increasing Zr contents, the lattice parameters and band gaps of SrRu1−xZrxO3 increase while the energy difference between antiferromagnetic and ferromagnetic states decreases. Through Ru-O and Zr-O bonds, hybridization between Ru 4d and Zr 4d states near the Fermi level becomes strong. As a result, Ru 4d states split and then metal-insulator transition occurs at x = 0.125 due to Zr. Ferromagnetic semiconductors are first predicted in SrRu1−xZrxO3 alloys, which may have potential applications in spintronic devices. [ABSTRACT FROM AUTHOR]

Control of the nonlinear transport properties in strongly correlated materials with metal–insulator transitions has become an important task in the development of next-generation computing elements. Here, we demonstrate that the nonlinear transport properties in the Mott insulator Ca2RuO4, which are caused by the current-driven transition with a nonthermal-type mechanism, can be significantly affected by epitaxial strain in thin films. Ca2RuO4 epitaxial thin films were grown on various single-crystal substrates by the solid-phase epitaxy method under nonvacuum conditions, and the effects of epitaxial strain on the transport properties were investigated. While nonlinear transport properties with negative differential resistance behavior were observed in [001]-oriented Ca2RuO4/LaAlO3 (001) thin films, the current transport nonlinearity was critically diminished in the current–voltage characteristics of Ca2RuO4/NdCaAlO4 (100) thin films with the [110] orientation. Through structural characterization of the thin films, a possible correlation between the strain states and nonlinear transport properties was discussed. [ABSTRACT FROM AUTHOR]

Structural, magnetic and optical properties of double manganites PrBaMn2O6 and NdBaMn2O6 are studied depending on the degree of ordering in the A-position. It is shown that, annealing induced disordering goes in an initial stage throw formation of a two-phase state: a phase with a high A-site ordering with TC ∼ 280–300 K and a phase with a low ordering of ~30% with significantly lower TC coexist. In partially ordered PrBaMn2O6 samples there are metal-insulator transitions near TC of the each coexisting phases. In partially ordered NdBaMn2O6 in a highly A-site ordered high-temperature phase, there is no metal-insulator transition due to the destruction of the channels for metallic conductivity formed by the ordering of the x2‒y2 orbitals. If a metal-insulator transition takes place, the application of a magnetic field leads to the effect of magnetotransmission near TC, which is associated with a change in the concentration of delocalized charge carriers. [ABSTRACT FROM AUTHOR]

The multiple quantum transitions within d-band correlation oxides such as rare-earth nickelates (RENiO3) triggered by critical temperatures and/or hydrogenation opened up a new paradigm for correlated electronics applications, e.g. ocean electric field sensor, bio-sensor, and neuron synapse logical devices. Nevertheless, these applications are obstructed by the present ineffectiveness in the thin film growth of the metastable RENiO3 with flexibly adjustable rare-earth compositions and electronic structures. Herein, we demonstrate a metal-organic decompositions (MOD) approach that can effectively grow metastable RENiO3 covering a large variety of the rare-earth composition without introducing any vacuum process. Unlike the previous chemical growths for RENiO3 relying on strict interfacial coherency that limit the film thickness, the MOD growth using reactive isooctanoate percussors is tolerant to lattice defects and therefore achieves comparable film thickness to vacuum depositions. Further indicated by positron annihilation spectroscopy, the RENiO3 grown by MOD exhibit large amount of lattice defects that improves their hydrogen incorporation amount and electron transfers, as demonstrated by the resonant nuclear reaction analysis and near edge X-ray absorption fine structure analysis. This effectively enlarges the magnitude in the resistance regulations in particular for RENiO3 with lighter RE, shedding a light on the extrinsic regulation of the hydrogen induced quantum transitions for correlated oxides semiconductors kinetically via defect engineering. [ABSTRACT FROM AUTHOR]

We use a combination of density functional theory (DFT) and dynamical mean field theory (DMFT) to unveil orbital field-induced electronic structure reconstruction of the atomic Sn layer deposited onto a Si(111) surface (Sn/Si(111)−3×3R30∘), also referred to as α-Sn. Our DFT + DMFT results indicate that α-Sn is an ideal testing ground to explore electric field-driven orbital selectivity and Mott memory behavior, all arising from the close proximity of α-Sn to metal insulator transitions. We discuss the relevance of orbital phase changes for α-Sn in the context of the current–voltage (I−V) characteristic for future silicon-based metal semiconductor atomristors.

Abstract The metal–insulator transition (MIT) observed in vanadium dioxide has been a topic of great research interest for past decades, with the underlying physics yet not fully understood due to the complex electron interactions and structures involved. The ability to understand and tune the MIT behavior is of vital importance from the perspective of both underlying fundamental science as well as potential applications. In this work, scanning transmission electron microscopy (STEM) is used to investigate cross‐section lamella of the VO2 films deposited using pulsed laser deposition on three substrates: c‐cut sapphire, TiO2(101) and TiO2(001). Advanced STEM imaging is performed in which also the oxygen atom columns are resolved. The overall film quality and structures on atomic and nanoscale are linked to the electrical transition characteristics. Relatively poor MIT characteristics are observed on c‐sapphire due to the presence of very small domains with six orientation variants, and on TiO2 (001) due to the presence of cracks induced by stress relaxation. However, the MIT on TiO2 (101) behaves favorably, despite similar stress relaxation which, however, only leads to domain boundaries but no cracks.

The ability to manipulate spins in magnetic materials is essential in designing spintronics devices. One method for magnetic switching is through strain. In VO 2 on TiO 2 thin films, while VO 2 remains rutile across the metal–insulator transition, the in-plane lattice area expands going from a low-temperature insulating phase to a high-temperature conducting phase. In a VO 2 /TbFeCo bilayer, the expansion of the VO 2 lattice area exerts tension on the amorphous TbFeCo layer. Through the strain effect, magnetic properties, including the magnetic anisotropy and magnetization, of TbFeCo can be changed. In this work, the changes in magnetic properties of TbFeCo on VO 2 /TiO 2 (011) are demonstrated using anomalous Hall effect measurements. Across the metal–insulator transition, TbFeCo loses perpendicular magnetic anisotropy, and the magnetization in TbFeCo turns from out-of-plane to in-plane. Using atomistic simulations, we confirm these tunable magnetic properties originating from the metal–insulator transition of VO 2 . This study provides the groundwork for controlling magnetic properties through a phase transition. [ABSTRACT FROM AUTHOR]

Molybdenum ditelluride (MoTe2) exhibits immense potential in post-silicon electronics due to its bandgap comparable to silicon. Unlike other 2D materials, MoTe allows easy phase modulation and efficient carrier type control in electrical transport. However, its unstable nature and low-carrier mobility limit practical implementation in devices. Here, a deterministic method is proposed to improve the performance of MoTe2 devices by inducing local tensile strain through substrate engineering and encapsulation processes. The approach involves creating hole arrays in the substrate and using atomic layer deposition grown Al2O3 as an additional back-gate dielectric layer on SiO2. The MoTe channel is passivated with a thick layer of Al2O3 post-fabrication. This structure significantly improves hole and electron mobilities in MoTe field-effect transistors (FETs), approaching theoretical limits. Hole mobility up to 130 cm-2 V-1 s-1 and electron mobility up to 160 cm-2 V-1 s-1 are achieved. Introducing local tensile strain through the hole array enhances electron mobility by up to 6 times compared to the unstrained devices. Remarkably, the devices exhibit metal-insulator transition in MoTe FETs, with a well-defined critical point. This study presents a novel technique to enhance carrier mobility in MoTe2 FETs, offering promising prospects for improving 2D material performance in electronic applications. [ABSTRACT FROM AUTHOR]

Ramp‐reversal memory has recently been discovered in several insulator‐to‐metal transition materials where a non‐volatile resistance change can be set by repeatedly driving the material partway through the transition. This study uses optical microscopy to track the location and internal structure of accumulated memory as a thin film of VO2 is temperature cycled through multiple training subloops. These measurements reveal that the gain of insulator phase fraction between consecutive subloops occurs primarily through front propagation at the insulator‐metal boundaries. By analyzing transition temperature maps, it is found, surprisingly, that the memory is also stored deep inside both insulating and metallic clusters throughout the entire sample, making the metal‐insulator coexistence landscape more rugged. This non‐volatile memory is reset after heating the sample to higher temperatures, as expected. Diffusion of point defects is proposed to account for the observed memory writing and subsequent erasing over the entire sample surface. By spatially mapping the location and character of non‐volatile memory encoding in VO2, this study results enable the targeting of specific local regions in the film where the full insulator‐to‐metal resistivity change can be harnessed in order to maximize the working range of memory elements for conventional and neuromorphic computing applications. [ABSTRACT FROM AUTHOR]

Due to metal–insulator transitions occurring in those compounds, materials and devices based on vanadium (III) and (IV) oxides draw increasing scientific attention. In this paper, we observed the transitions in both oxides using contemporary laboratory equipment. Changes in the crystallographic structure were precisely investigated as a function of the temperature with a step of 2 °C. Thermal effects during transitions were observed using differential scanning calorimetry. The DC conductivity of the materials was measured quasi-continuously as a function of the temperature. All the experiments were consistent and showed considerable hysteresis of the metal–insulator transition in both vanadium oxides. [ABSTRACT FROM AUTHOR]

Thermal radiation from a black body increases with the fourth power of absolute temperature (T4 ), an effect known as the Stefan-Boltzmann law. Typical materials radiate heat at a portion of this limit, where the portion, called integrated emissivity (εint ), is insensitive to temperature (|dεint /dT| ≈ 10-4 °C-1 ). The resultant radiance bound by the T4 law limits the ability to regulate radiative heat. Here, an unusual material platform is shown in which εint can be engineered to decrease in an arbitrary manner near room temperature (|dεint /dT| ≈ 8 × 10-3 °C-1 ), enabling unprecedented manipulation of infrared radiation. As an example, εint is programmed to vary with temperature as the inverse of T4 , precisely counteracting the T4 dependence; hence, thermal radiance from the surface becomes temperature-independent, allowing the fabrication of flexible and power-free infrared camouflage with unique advantage in performance stability. The structure is based on thin films of tungsten-doped vanadium dioxide where the tungsten fraction is judiciously graded across a thickness less than the skin depth of electromagnetic screening.

Abstract Ramp‐reversal memory has recently been discovered in several insulator‐to‐metal transition materials where a non‐volatile resistance change can be set by repeatedly driving the material partway through the transition. This study uses optical microscopy to track the location and internal structure of accumulated memory as a thin film of VO2 is temperature cycled through multiple training subloops. These measurements reveal that the gain of insulator phase fraction between consecutive subloops occurs primarily through front propagation at the insulator‐metal boundaries. By analyzing transition temperature maps, it is found, surprisingly, that the memory is also stored deep inside both insulating and metallic clusters throughout the entire sample, making the metal‐insulator coexistence landscape more rugged. This non‐volatile memory is reset after heating the sample to higher temperatures, as expected. Diffusion of point defects is proposed to account for the observed memory writing and subsequent erasing over the entire sample surface. By spatially mapping the location and character of non‐volatile memory encoding in VO2, this study results enable the targeting of specific local regions in the film where the full insulator‐to‐metal resistivity change can be harnessed in order to maximize the working range of memory elements for conventional and neuromorphic computing applications.