Pressure reduction of parasitic parallel conduction in InGaAs/InP heterostructures containing LT-InP layers

Abstract

We have measured classical and quantum (Shubnikov-de Haas effect) magnetotrans-port properties of InGaAs/InP heterostructures in which phosphorus antisite defects incorporated in low temperature MBE-grown InP (LT-InP) layers are the main source of electrons. The heterostructures show strong parasitic parallel conduction, which is reduced under hydrostatic pressure. The comparison of the experimental results with the calculations of the potential profile and the charge distribution in the heterostructures enables to identify all the conduction channels in the structures and unambiguously proves that the parasitic parallel conduction is due to spontaneous formation of the quantum well in the LT-InP buffer.     

Magnetic proximity effect induced spin splitting in two-dimensional antimonene/Fe3GeTe2 van der Waals heterostructures

Recently, two-dimensional van der Waals (vdW) magnetic heterostructures have attracted intensive attention since they can show remarkable properties due to the magnetic proximity effect. In this work, the spin-polarized electronic structures of antimonene/Fe₃GeTe₂ vdW heterostructures were investigated through the first-principles calculations. Owing to the magnetic proximity effect, the spin splitting appears at the conduction-band minimum (CBM) and the valence-band maximum (VBM) of the antimonene. A low-energy effective Hamiltonian was proposed to depict the spin splitting. It was found that the spin splitting can be modulated by means of applying an external electric field, changing interlayer distance or changing stacking configuration. The spin splitting energy at the CBM monotonously increases as the external electric field changes from -5 V/nm to 5 V/nm, while the spin splitting energy at the VBM almost remains the same. Meanwhile, as the interlayer distance increases, the spin splitting energies at the CBM and VBM both decrease. The different stacking configurations can also induce different spin splitting energies at the CBM and VBM. Our work demonstrates that the spin splitting of antimonene in this heterostructure is not singly dependent on the nearest Sb—Fe distance, which indicates that magnetic proximity effect in heterostructures may be modulated by multiple factors, such as hybridization of electronic states and the local electronic environment. The results enrich the fundamental understanding of the magnetic proximity effect in two-dimensional vdW heterostructures.     

Construction of Hierarchical Hollow Co9S8/ZnIn2S4 Tubular Heterostructures for Highly Efficient Solar Energy Conversion and Environmental Remediation

Visible‐light‐responsive hierarchical Co₉S₈/ZnIn₂S₄ tubular heterostructures are fabricated by growing 2D ZnIn₂S₄ nanosheets on 1D hollow Co₉S₈ nanotubes. This design combines two photoresponsive sulfide semiconductors in a stable heterojunction with a hierarchical hollow tubular structure, improving visible‐light absorption, yielding a large surface area, exposing sufficient catalytically active sites, and promoting the separation and migration of photogenerated charges. The hierarchical nanotubes exhibit excellent photocatalytic H₂ evolution and Cr^VI reduction efficiency. Under visible‐light illumination, the optimized Co₉S₈/ZnIn₂S₄ heterostructure provides a remarkable H₂ generation rate of 9039 μmol h^?1 g^?1 without the use of any co‐catalysts and Cr^VI is completely reduced in 45 min. The Co₉S₈/ZnIn₂S₄ heterostructure is stable after multiple photocatalytic cycles.     

Ag2O/TiO2异质结的光催化活性及耐光腐蚀性研究

以钛酸丁酯、硝酸铋和硝酸银为原料,FTO为基底,采用水热法结合超声沉积法合成了Ag2 O/TiO2异质结光催化剂.采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)、紫外-可见吸收光谱(UV-Vis)分析测试手段对样品的形貌和结构进行了表征.结果表明,Ag2O/TiO2异质结是由直径约200 ～ 300 nm的TiO2纳米棒镶嵌着Ag2O纳米颗粒组成,与TiO2纳米棒阵列相比,Ag2O/TiO2异质结在可见光区有明显的光吸收.Ag2O/TiO2异质结的光催化效率明显提高.尤为重要的是,经光处理后,最终得到稳定的Ag-Ag2O/TiO2三元体系,并对Ag-Ag2 O/TiO2三元体系提高光催化稳定性和活性的机理进行了分析.     

Efficient Visible‐Light‐Driven Z‐Scheme Overall Water Splitting Using a MgTa2O6−xNy /TaON Heterostructure Photocatalyst for H2 Evolution

An (oxy)nitride‐based heterostructure for powdered Z‐scheme overall water splitting is presented. Compared with the single MgTa₂O_6?xN_y or TaON photocatalyst, a MgTa₂O_6?xN_y /TaON heterostructure fabricated by a simple one‐pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt‐loaded MgTa₂O_6?xN_y /TaON as a H₂‐evolving photocatalyst, a Z‐scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8 % at 420 nm was constructed (PtO_x‐WO₃ and IO₃^?/I^? pairs were used as an O₂‐evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt‐TaON or Pt‐MgTa₂O_6?xN_y as a H₂‐evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z‐scheme overall water splitting systems ever reported.     

离子导体载流子输运与存储的界面调控

离子导电材料既可以是载流子主要为离子的纯离子导体,也可以是载流子同时包括离子和电子的混合离子导体.这两类材料是电化学能量转换与储存、化学传感以及选择性透过膜等器件的关键材料.在这些器件中,均存在电极与电解质、颗粒与颗粒、不同晶粒之间的二维或三维的异质结界面.因此,离子与电子在异质结中的输运性质对器件性能有重要的影响.但异质结的组成与结构如何影响载流子输运与存储的科学机理还远未得到澄清.与不规则的实际应用的粉体材料相比,二维离子导电异质结对于揭示界面作用机制具有显著的优势,这方面的研究刚刚起步.文章将着重介绍二维离子导电异质结的研究背景与研究进展、已经观察到的典型界面效应、载流子输运与存储特性,并对利用界面效应对材料的离子输运与存储的调控作简要评述.     

Ultrathin ZnIn2S4 Nanosheets Anchored on Ti3C2TX MXene for Photocatalytic H2 Evolution

Photocatalysts derived from semiconductor heterojunctions that harvest solar energy and catalyze reactions still suffer from low solar‐to‐hydrogen conversion efficiency. Now, MXene (Ti₃C₂T_X) nanosheets (MNs) are used to support the in situ growth of ultrathin ZnIn₂S₄ nanosheets (UZNs), producing sandwich‐like hierarchical heterostructures (UZNs‐MNs‐UZNs) for efficient photocatalytic H₂ evolution. Opportune lateral epitaxy of UZNs on the surface of MNs improves specific surface area, pore diameter, and hydrophilicity of the resulting materials, all of which could be beneficial to the photocatalytic activity. Owing to the Schottky junction and ultrathin 2D structures of UZNs and MNs, the heterostructures could effectively suppress photoexcited electron–hole recombination and boost photoexcited charge transfer and separation. The heterostructure photocatalyst exhibits improved photocatalytic H₂ evolution performance (6.6 times higher than pristine ZnIn₂S₄) and excellent stability.     

Spatial structures of islands of electron-hole liquid in semiconductor quantum wells

The formation of the different structures of islands of electron-hole liquid in the quantum well is studied in a statistical model. The interaction between the islands of electron-hole liquid is considered by influencing of neighboring islands through exciton gas around the considered island. Two restricted regions were studied: an infinite strip and a disk. The theory gives the possibility to determine the probability of different states realization and to find the most probable state. The dependence of the radius, mutual positions of the electron-hole liquid islands, the number of the islands in the disk on the pumping, temperature and parameters of the system (the size and the shape) are calculated.