Vanadium-Doped Semi-Insulating 6H-SiC for Microwave Power Device Applications

Two-inch semi-insulating SiC bulk crystals with resistivity higher than 1 × 10^6 Qcm were achieved by vanadium doping during sublimation. Secondary-ion-mass-spectrometry （SIMS） was employed to determine the concentration of impurities in the crystals, such as B, AI, V and N. These results indicated that the concentration of nitrogen and aluminum kept on decreasing and the concentration of B and V was almost constant during the whole growth. An inner crucible was used to control the exhausting of vanadium, which made the uniformity of the high resistivity （〉1×10^6 Ωcm） in the wafer up to 80%. High-performance AlGaN/GaN high-electronmobility-transistor （HEMT） materials and devices were grown and fabricated on semi-insulating 6H-SiC sub- strates. The two-dimensional electron gas （2DEG） mobility at room-temperature was 1795 cm^2/V-s. The charge carrier concentration of the substrate determined by capacitance-voltage （C-V） test was 7.3×10^15 cm^-3. The device with a gate width of I mm exhibits a maximum output power of 5.5 W at 8 GHz, which proves the semi-insulating property of the substrates indirectly.

Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO2 thin films as efficient electron transport layer

We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly（3-hexylthiophene） P3HT：[6-6] phenyl-（6） butyric acid methyl ester（PCBM）. 1% vanadium-doped TiO2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO2 thin film showed slightly higher power conversion efficiency and great Jsc of 10.7 mA/cm^2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO2 thin film was better in all wavelengths.

Robust route to H_(2)O_(2)and H_(2)via intermediate water splitting enabled by capitalizing on minimum vanadium-doped piezocatalysts

H_(2)O_(2)is an environmentally friendly chemical for a wide range of water treatments.The industrial production of H_(2)O_(2)is an anthraquinone oxidation process,which,however,consumes extensive energy and produces pollution.Here we report a green and sustainable piezocatalytic intermediate water splitting process to simultaneously obtain H_(2)O_(2)and H_(2)using single crystal vanadium(V)-doped NaNbO_(3)(V-NaNbO_(3))nanocubes as catalysts.The introduction of V improves the specific surface area and active sites of NaNbO_(3).Notably,V-NaNbO_(3)piezocatalysts of 10 mg exhibit 3.1-fold higher piezocatalytic efficiency than the same catalysts of 50 mg,as more piezocatalysts lead to higher probability of aggregation.The aggregation causes reducing active sites and decreased built-in electric field due to the neutralization between different nano-catalysts.Remarkably,piezocatalytic H_(2)O_(2)and H_(2)production rates of V-NaNbO_(3)(10 mol%)nanocubes(102.6 and 346.2μmol·g^(−1)·h^(−1),respectively)are increased by 2.2 and 4.6 times compared to the as-prepared pristine NaNbO_(3)counterparts,respectively.This improved catalytic efficiency is attributed to the promoted piezo-response and more active sites of NaNbO_(3)catalysts after V doping,as uncovered by piezoresponse force microscopy(PFM)and density functional theory(DFT)simulation.More importantly,our DFT results illustrate that inducing V could reduce the dynamic barrier of water dissociation over NaNbO_(3),thus enhancing the yield of H_(2)O_(2)and H_(2).This facile yet robust piezocatalytic route using minimal amounts of catalysts to obtain H_(2)O_(2)and H_(2)may stand out as a promising candidate for environmental applications and water splitting.

Visualization of ferromagnetic domains in vanadium-doped topological insulator thin films and heterostructures

Magnetically doped topological insulator(TI) thin films and related heterostructures have been extensively studied for years due to their exotic quantum transport properties and potential applications in low-dissipation electronic devices and quantum computation.The selection of magnetic dopants is crucial to realize a high-quality magnetic TI with a robust ferromagnetic ordering and a preserved topological band structure.In this paper,we briefly review the recent magnetic domain imaging works in vanadium-doped magnetic topological insulator thin films and heterostructures.Using cryogenic magnetic force microscopy and in situ transport measurements,a ferromagnetic domain behavior has been demonstrated in V-doped Sb2Te3(ST) and Cr,V co-doped(Bi,Sb)2Te3(BST) thin films.The direct visualization of long-range ferromagnetic ordering in a quantum anomalous Hall(QAH) system sheds light on enhancing the QAH temperature by improving the ferromagnetism.Taking advantage of the different coercivity of Cr-and V-doped BST films,an axion insulating state has been observed in Cr-doped BST/BST/V-doped BST sandwich heterostructures.The antiparallel magnetization alignment,which is the key ingredient for realization of axion insulating state,has been directly visualized via magnetic imaging at various magnetic fields.The V-doped ST/ST heterostructures also provide a platform for Berry phase engineering in momentum space.By suppressing the anomalous Hall effect in such heterostructures,an intrinsic topological Hall effect can be revealed,which resolved the long-term puzzle of the origin of THE in the ultrathin ferromagnetic thin films and two-dimensional ferromagnets.The review of magnetic domain imaging in vanadium-doped topological insulators and heterostructures inspires further exploration of quantum transport properties in magnetic topological insulators and deepens the understanding of the interplay between the magnetic ordering and topological electronic band structures in magnetic TIs and beyond.

Ultra‑Transparent and Multifunctional IZVO Mesh Electrodes for Next‑Generation Flexible Optoelectronics

Mechanically durable transparent electrodes are essential for achieving long-term stability in flexible optoelectronic devices.Furthermore,they are crucial for applications in the fields of energy,display,healthcare,and soft robotics.Conducting meshes represent a promising alternative to traditional,brittle,metal oxide conductors due to their high electrical conductivity,optical transparency,and enhanced mechanical flexibility.In this paper,we present a simple method for fabricating an ultra-transparent conducting metal oxide mesh electrode using selfcracking-assisted templates.Using this method,we produced an electrode with ultra-transparency(97.39%),high conductance(Rs=21.24Ωsq^(−1)),elevated work function(5.16 eV),and good mechanical stability.We also evaluated the effectiveness of the fabricated electrodes by integrating them into organic photovoltaics,organic light-emitting diodes,and flexible transparent memristor devices for neuromorphic computing,resulting in exceptional device performance.In addition,the unique porous structure of the vanadium-doped indium zinc oxide mesh electrodes provided excellent flexibility,rendering them a promising option for application in flexible optoelectronics.