Electron g-factor in a gated InAs-inserted-channel In0.53Ga0.47As/In0.52Al0.48As heterostructure

We report on electron g-factor in an InAs-inserted In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructure. The gate voltage dependence of g-factor is obtained from the coincidence method. The obtained g-factor values are surprisingly smaller than the g-factor value of bulk InAs, and it is close to the bare g-factor value of In_0.53Ga_0.47As. The large change in g-factor is observed by applying the gate voltage. The obtained gate voltage dependence is not simply explained by the energy dependence of g-factor.     

Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors

SiN_x is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN_x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiN_x films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results.     

Prediction of quantum anomalous Hall effect in CrI3/ScCl2 bilayer heterostructure

Based on first-principles calculations, a two-dimensional (2D) van der Waals (vdW) bilayer heterostructure consisting of two topologically trivial ferromagnetic (FM) monolayers CrI₃ and ScCl₂ is proposed to realize the quantum anomalous Hall effect (QAHE) with a sizable topologically nontrivial band gap of 4.5 meV. Its topological nature is attributed to an interlayer band inversion between the monolayers and critically depends on the symmetry of the stacking configuration. We further demonstrate that the topologically nontrivial band gap can be increased nearly linearly by the application of a perpendicular external pressure and reaches 8.1 meV at 2.7 GPa, and the application of an external out-of-plane electric field can also modulate the band gap and convert the system back to topologically trivial via eliminating the band inversion. An effective model is developed to describe the topological phase evolution in this bilayer heterostructure. This work provides a new candidate system based on 2D vdW materials for realization of potential high-temperature QAHE with considerable controllability.     

Facile synthesis of Z-scheme NiO/α-MoO3 p-n heterojunction for improved photocatalytic activity towards degradation of methylene blue

In this article, Z-scheme NiO/α-MoO₃ p-n heterojunction is successfully synthesized by a facile hydrothermal route. The phase and nanostructures are researched through a series of characterizations, such as XRD, SEM, TEM, EDX, XPS and DRS. It is confirmed that the NiO nanoparticles are deposited homogeneously on one dimensional α-MoO₃ nanobelts and p-n heterojuction is constructed at the interface of α-MoO₃ and NiO. Photocatalytic activity of the as-synthesized photocatalysts is investigated by photodegradation of methylene blue (MB) under simulated solar light irradiation. Compared with bare α-MoO₃, the NiO/α-MoO₃ p-n heterojunction exhibits significantly improved photocatalytic activity and photostability for MB degradation. The improvement in the photocatalytic performance can be attributed to the optimization of the charge transport pathway offered by Z-scheme heterojunctions, which can promote the effective separation of electron-hole pairs. The results indicate that Z-scheme NiO/α-MoO₃ p-n heterojunction is a novel and efficient photocatalyst with potential application for the removal of organic contaminant in wastewater.     

Electrospinning synthesis and photocatalytic property of CaFe2O4/MgFe2O4 heterostructure for degradation of tetracycline

CaFe₂O₄/MgFe₂O₄ nanowires with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X‐Ray diffraction (XRD), UV–Vis diffuse reflectance spectra (UV‐Vis DR) and Environment scanning electron microscopy (ESEM). The novel CaFe₂O₄/MgFe₂O₄ nanowires exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare CaFe₂O₄ or MgFe₂O₄ samples, the prepared CaFe₂O₄/MgFe₂O₄ (Ca:Mg:Fe = 3:2:10) composited nanowires show the best photocatalytic performance with a degradation efficiency of 40% after 150 min reaction time. This enhancement is attributed to the heterostructure of CaFe₂O₄/MgFe₂O₄ nanowires, which effectively repress the recombination of photo‐generated electrons and holes. Based on heterostructure and energy band positions, the enhancement of mechanism under visible‐light enhances the photocatalytic activity.     

Heterojunction of BiPO4/BiOBr photocatalysts for Rhodamine B dye degradation under visible LED light irradiation

BiOBr synthesized by alcoholysis precipitation is used in the preparation of BiPO₄/BiOBr composites by adding H₃PO₄. Pristine BiOBr and a series of BiPO₄/BiOBr composites have been successfully synthesized using an entirely room-temperature production process. X-ray powder diffraction, scanning electron microscopy, High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy were used to investigated the bulk structure, surface morphology, element composition and optical properties of the samples. The degradation effect of different proportions of BiPO₄/BiOBr composites, BiOBr and BiPO₄ on Rhodamine B (RhB) was evaluated under visible LED light irradiation. Compared to pure BiOBr and BiPO₄, the as-synthesized BiPO₄/BiOBr composites showed enhanced performance, with 30% BiPO₄/BiOBr composite showing the best performance, as it could degrade 95.66% of RhB (100 ml, 15 mg/L) within 120 min. The enhanced photocatalytic activity of BiPO₄/BiOBr was attributed to the heterojunction formation between BiOBr and BiPO₄ and efficient charge separation.     

Co9S8/MoS2异质结构的构筑及电催化析氢性能研究

利用前驱物形貌导向法,成功制备了Co₉S₈/MoS₂异质结构催化剂,该催化剂在碱性析氢反应（HER）中表现出优异的催化活性及稳定性,其在10 mA·cm^-2处的过电势仅为84 mV.通过X射线粉末衍射（XRD）、透射电子显微镜（TEM）、电子自旋共振（ESR）、拉曼光谱（Raman）、X射线光电子能谱（XPS）和同步辐射（XAFS）等表征,证明了CoS₂/MoS₂在H₂氛围下煅烧形成Co₉S₈/MoS₂的过程中,CoS₂中Co的配位模式从部分八面体向Co₉S₈中的四面体转变,这种转变可活化MoS₂的惰性平面,从而使其更有利于吸附H^*.除此之外,接触角数据表明：该催化剂具有良好的亲水性,有利于电解液渗透及气体分子的迅速扩散,从而促进HER反应速率.由于异质结构间具有强烈的相互作用,该催化剂可表现出良好的结构稳定性.本工作基于Co₉S₈/MoS₂异质结构的成功构筑及对其HER催化机理的充分探讨,为后续硫化物异质结及其在电催化中的应用提供了良好的思路和研究基础.     

Tuning the electronic properties of hydrogen passivated C3N nanoribbons through van der Waals stacking

The two-dimensional (2D) C₃N has emerged as a material with promising applications in high performance device owing to its intrinsic bandgap and tunable electronic properties. Although there are several reports about the bandgap tuning of C₃N via stacking or forming nanoribbon, bandgap modulation of bilayer C₃N nanoribbons (C₃NNRs) with various edge structures is still far from well understood. Here, based on extensive first-principles calculations, we demonstrated the effective bandgap engineering of C₃N by cutting it into hydrogen passivated C₃NNRs and stacking them into bilayer heterostructures. It was found that armchair (AC) C₃NNRs with three types of edge structures are all semiconductors, while only zigzag (ZZ) C₃NNRs with edges composed of both C and N atoms (ZZCN/ CN) are semiconductors. The bandgaps of all semiconducting C₃NNRs are larger than that of C₃N nanosheet. More interestingly, AC-C₃NNRs with CN/CN edges (AC-CN/CN) possess direct bandgap while ZZ-CN/CN have indirect bandgap. Compared with the monolayer C₃NNR, the bandgaps of bilayer C₃NNRs can be greatly modulated via different stacking orders and edge structures, varying from 0.43 eV for ZZ-CN/CN with AB′-stacking to 0.04 eV for AC-CN/CN with AA-stacking. Particularly, transition from direct to indirect bandgap was observed in the bilayer AC-CN/CN heterostructure with AA′-stacking, and the indirect-to-direct transition was found in the bilayer ZZ-CN/CN with ABstacking. This work provides insights into the effective bandgap engineering of C₃N and offers a new opportunity for its applications in nano-electronics and optoelectronic devices.     

Synthesis and Characterization of an α-Fe2O3-Decorated g-C3N4 Heterostructure for the Photocatalytic Removal of MO

This study describes the preparation of graphitic carbon nitride (g-C₃N₄), hematite (α-Fe₂O₃), and their g-C₃N₄/α-Fe₂O₃ heterostructure for the photocatalytic removal of methyl orange (MO) under visible light illumination. The facile hydrothermal approach was utilized for the preparation of the nanomaterials. Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) were carried out to study the physiochemical and optoelectronic properties of all the synthesized photocatalysts. Based on the X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance (DRS) results, an energy level diagram vs. SHE was established. The acquired results indicated that the nanocomposite exhibited a type-II heterojunction and degraded the MO dye by 97%. The degradation ability of the nanocomposite was higher than that of pristine g-C₃N₄ (41%) and α-Fe₂O₃ (30%) photocatalysts under 300 min of light irradiation. The formation of a type-II heterostructure with desirable band alignment and band edge positions for efficient interfacial charge carrier separation along with a larger specific surface area was collectively responsible for the higher photocatalytic efficiency of the g-C₃N₄/α-Fe₂O₃ nanocomposite. The mechanism of the nanocomposite was also studied through results obtained from UV-vis and XPS analyses. A reactive species trapping experiment confirmed the involvement of the superoxide radical anion (O₂^•−) as the key reactive oxygen species for MO removal. The degradation kinetics were also monitored, and the reaction was observed to be pseudo-first order. Moreover, the sustainability of the photocatalyst was also investigated.     

三氧化钨/氧化银复合材料的水热法合成及其光催化降解性能研究

染料污染是水污染中最严重的问题之一,吸引了很多科学家的关注.人们尝试了很多方法去解决该问题,如化学氧化法、物理吸附法、光催化降解法和生物降解法等.与其他几种方法相比,光催化法有着低能耗、环保以及高效等优势.三氧化钨是常见的半导体材料,具有独特的光学性能,近年来受到了广泛的研究.本文以钨酸钠和硫脲为前驱体,通过水热法制备了三氧化钨/氧化银(WO_3/Ag_2O)复合材料,并用光催化降解亚甲基蓝来分析其光催化性能.通过X射线光电子能谱、X射线衍射、透射电子显微镜、扫描电子显微镜、紫外可见吸收光谱等表征手段对样品的形貌、晶格结构和光催化的性能进行表征.氧化银的带宽为1.2 e V,对可见光很敏感,三氧化钨和氧化银的复合使材料在可见光下的光催化活性显著增强,在可见光下对亚甲基蓝染料的光降解率可以达到98%.实验结果表明,复合材料中的三氧化钨纳米棒为六方相,其平均直径约为200 nm,平均长度约为4μm.而复合材料中的氧化银纳米颗粒为六方相,附着在氧化钨纳米棒的表面,平均晶粒尺寸为20 nm.氧化银的存在为复合材料提供了更多的反应活性位点.相较于单一组分,复合材料在可见光下的光吸收度更高,这说明三氧化钨和氧化银的复合改变了材料的能带结构.研究发现,三氧化钨和氧化银之间形成的异质结构是其优良光催化性能的来源.此外,三氧化钨和氧化银复合材料还具有良好的催化稳定性和化学稳定性.本文结果表明,可以通过给宽带隙的半导体材料复合一些带隙合适的金属氧化物以提升其光催化活性.