Review MXenes as a new type of nanomaterial for environmental applications in the photocatalytic degradation of water pollutants

Two-dimensional titanium carbide (MXene) with an adjustable bandgap (0.92–1.75eV), excellent structural stability, high conductivity and hydrophilicity has always been a hotspot in the field of environmental photocatalysis. However, the rapid recombination of light-excited carriers of a single photocatalytic material decreases quantum efficiency and photocatalytic performance. The modification of MXene could overcome these problems to improve photocatalytic properties. Among various improvement strategies, the composition of MXene heterostructure and Schottky junction is an effective and straightforward strategy for adjusting electronic structure and accelerating photocatalytic performance. This review aims to design typical, cost-effective heterojunctions and Schottky junctions and their progress, mechanisms, and trends in environmental organic pollutants' degradation. This review detailed the heterogeneous catalytic mechanism of MXene-based photocatalysts for the degradation of organic pollutants. It is discussed the way to improve the photocatalytic performance of MXene by constructing heterojunction and Schottky junction. The surface properties, catalyst performance and pollution management of various MXene-based catalysts were compared, and then some dilemmas and application strategies of MXene development were analyzed in depth. This review can open up ideas for new approaches and provide valuable clues for designing MXene as a cocatalyst to develop more effective photocatalysts for practical application in environmental pollution management.     

Non-equilibrium charge carriers generation — recombination mechanisms at the interface of the SnO2/GaSe heterojunction

The interface of the SnO₂/GaSe heterojunctions, having SnO₂ layer obtained by different deposition methods have been studied using the photoluminescence and photocurrent spectral distribution. The SnO₂/GaSe structures are photosensitive in the 1.7 ÷ 3.6 eV spectral range and reveal its maximum value for the heterojunctions with magnetron sputtered SnO₂ layer.     

Evaluation of InP-to-silicon heterobonding

In this paper, we evaluate hydrophilic (HP) and hydrophobic (HB) surface pre-treatments in InP-to-Si direct wafer bonding. Surface roughness and surface chemistry was examined using atomic force microscopy and X-ray photoelectron spectroscopy, respectively. After bonding, the bonded interfaces were evaluated using infrared transmission imaging, bond-strength and current–voltage (I–V) measurements. It was found that HP surface treatment using oxygen plasma makes room temperature bonding of InP and Si very spontaneous, and results in high bond-strengths already after low-temperature annealing. This was not observed when using standard oxidising acids as HP surface treatment before bonding. HB InP and Si surfaces, also, did not prove to bond spontaneously at room temperature and the bond-strength started to increase only after annealing at about 400°C. HB bonding and annealing at 400°C was though the best choice regarding the electrical characteristics of the bonded InP/Si heterojunction.     

A面和C面AlGaN/GaN异质结的比较研究

采用MOCVD技术在R面和C面蓝宝石上生长非极性A面和极性C面AlGaN/GaN异质结。分别用X射线衍射仪和原子力显微镜比较了两种材料的结构特性及表面形貌,通过电容-电压测试比较了两种材料的电学特性。研究结果表明,较高浓度的二维电子气的存在使得极性材料在微波功率器件方面更有优势,而非极性材料可以消除与极化相关的电场,更适合应用于光电器件领域。     

Fly ash cenospheres as multifunctional supports of g-C3N4/N-TiO2 with enhanced visible-light photocatalytic activity and adsorption

The ternary composites of g-C₃N₄/N-TiO₂/FACs (FAC: Fly Ash Cenospheres) were synthesized by an in-situ hydrolysis method to improve the photocatalytic activity and their stability. When TiO₂ was anchored on FAC, it was easily to be separated from the aqueous solution and could be repeatedly utilized. In the present experiments, the degradation rate remained for more than 68% even after the composite reused for seven times. The band gap of g-C₃N₄/N-TiO₂/FAC was 2.75?eV, which might be owing to the synergistic effect between N-TiO₂ and g-C₃N₄. The composite of g-C₃N₄/N-TiO₂/FAC had an ideal activity of 72.2% under visible light illumination for 180?min. It was about 1.3 times of N-TiO₂/FAC and 3.5 times of g-C₃N₄. The synergistic effect of SiO₂, Fe₂O₃ and TiO₂ components resulted to the improvement of photocatalytic performance.     

Double-polysilicon SiGe HBT architecture with lateral base link

We present an analysis of a modified double-polysilicon SiGe:C HBT module showing a CML ring oscillator gate delay τ_D of 2.5 ps, and f_T/f_max/BV_CEo values of 300 GHz/350 GHz/1.85 V (Fox et al., 2008) [1]. A key feature of the HBT module is a connection of the extrinsic and intrinsic base regions by lateral epitaxial overgrowth, which aims to overcome the limits of the conventional double-polysilicon architecture in simultaneously reducing R_B and C_BC. Potential benefits and barriers of the proposed device structure on the way to higher performance are reviewed with regard to the recently demonstrated performance gain of the classical double-polysilicon approach. The paper addresses technological challenges one is faced when the here presented device structure is scaled to minimum device dimensions.