银纳米颗粒/聚(乙撑二氧噻吩)修饰的硅纳米线阵列的合成及可见光催化性能研究

硅纳米线阵列由于其较强的光吸收能力及硅材料的丰富储量,被认为是最具大规模应用潜力的可见光光催化剂.针对硅材料在水相环境中不稳定这一瓶颈问题,本文提出了对硅纳米线阵列"先稳定、再活化"的修饰策略.通过在硅纳米线表面修饰聚(乙撑二氧噻吩)使其稳定,之后再修饰银纳米颗粒以提高光催化效率,得到了高效、稳定的可见光光催化剂.并通过研究聚(乙撑二氧噻吩)的厚度及银纳米颗粒的担载量对光催化剂性能的影响,得到了最佳的修饰条件.     

Fabrication and tribological properties of super-hydrophobic surfaces based on porous silicon

In the present work, super-hydrophobic surfaces based on porous silicon (PS) were constructed by the self-assembled molecular films and their tribological properties were investigated. A simple chemical etching approach was developed to fabricate PS with the certain rough microstructure surface, which can be observed by the environmental scanning electron microscopy (ESEM). The hydrocarbon and fluorocarbon alkylsilane molecular films were self-assembled on PS, which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. In contrast to PS, the alkylsilane molecular films modified PS (mPS) were super-hydrophobic since the apparent water contact angle (CA) exceeded 160°. The tribological properties of PS and the mPS were investigated by a ball-on-disk tribometer during the processes of different sliding velocities and normal loads. The experimental results showed that the alkylsilane molecular films could decrease the friction coefficient. Due to the difference of chain structure and functional groups, the fluorinated alkylsilane films are better candidates for improving the hydrophobicity and lubricating characteristics of PS comparing to the non-fluorinated ones. The carbon chain length of alkylsilane molecules self-assembling on the Si or PS substrates could have little effects on the hydrophobic properties and the tribology performances.     

一种实现光子晶体波导定向耦合型多路光均分的新方法

将多光子晶体单模波导平行、邻近放置构成定向耦合器. 依据自映像原理,数值分析了输入光场对称入射时,该系统中光的传播行为. 基于此结构,以三、四通道为例,设计了超微多路光分束器,并仅通过对称地改变耦合区中两个介质柱的有效折射率,使光场在横向发生重新分布,实现了输出能量的均分或自由分配. 和已报道结果相比,此调制方法更为简单易行而且效率更高,并可以推广到具有更多输出通道的光分束器中,在未来的集成光回路中具有广泛的应用价值. 关键词： 光子晶体波导 定向耦合器 分束器 能量均分     

A comparison of silicon oxide and nitride as host matrices on the photoluminescence from Er+ ions

This paper compares the properties of silicon oxide and nitride as host matrices for Er ions.Erbium-doped silicon nitride films were deposited by a plasma-enhanced chemical-vapour deposition system.After deposition,the films were implanted with Er3+ at different doses.Er-doped thermal grown silicon oxide films were prepared at the same time as references.Photoluminescence features of Er3+ were inspected systematically.It is found that silicon nitride films are suitable for high concentration doping and the thermal quenching effect is not severe.However,a very high annealing temperature up to 1200° C is needed to optically activate Er3+,which may be the main obstacle to impede the application of Er-doped silicon nitride.     

Passivation of defect states in surface and edge regions on pn-junction Si solar cells by use of hydrogen cyanide solutions

The local photovoltage of the pn-junction single-crystalline silicon solar cells observed by spot light scanning gradually decreases in the vicinity of edges. The energy conversion efficiency is increased by shadowing the edge regions where the local photovoltage is lower, showing that the defect density is high in the edge regions. From the analysis of the local photovoltage, the spacial distribution of defect states is obtained. The cyanide method, i. e., immersion of solar cells in HCN solutions at room temperature, increases the local photovoltage and increases the energy conversion efficiency.      

β-FeSi2薄膜制备与发光研究的进展

过渡金属硅化物β-FeSi₂因其原料价格低廉且利于环保而成为理想的硅基发光材料之一。探讨了β-FeSi₂的发光机理,介绍了几种β-FeSi₂薄膜制备方法并比较了不同制备方法的特点,总结了最近几年来β-FeSi₂的研究进展和主要研究结果。结合作者已经取得的结果和积累的经验,提出了提高材料发光性能方法,认为良好的结晶质量和尽可能减少缺陷是β-FeSi₂高效发光的基础,因此有必要探索新的制备方法并改善已有的制备工艺。另外,尝试在β-FeSi₂薄膜中应用其它元素,也有可能增大发光效率;而有效激发β-FeSi₂的p-i-n结构也是提高发光效率的方法之一。最后,讨论了β-FeSi₂的发展趋势,展望了该种材料的发展前景。     

Acoustic spectroscopy and electrical characterization of SiO2/Si structures with ultrathin SiO2 layers formed by nitric acid oxidation

Ultrathin silicon dioxide (SiO₂) layers formed on Si substrate with nitric acid have been investigated using both acoustic deep-level transient spectroscopy (A-DLTS) and electrical methods to characterize the interface states. The set of SiO₂/Si structures formed in different conditions (reaction time, concentrations of nitric acid (HNO₃), and SiO₂ thickness [3–9 nm]) was prepared. The leakage current density was decreased by post-oxidation annealing (POA) treatment at 250°C in pure nitrogen for 1 h and/or post-metallization annealing (PMA) treatment at 250°C in a hydrogen atmosphere for 1 h. All structures of the set, except electrical investigation, current-voltage (I - V), and capacitance — voltage (C - V) measurements, were investigated using A-DLTS to find both the interface states distribution and the role of POA and/or PMA treatment on the interface-state occurrence and distribution. The evident decreases of interface states and shift of their activation energies in the structures with PMA treatment in comparison with POA treatment were observed in most of the investigated structures. The results are analyzed and discussed.      

Ultrafast laser written active devices

Direct‐write optical waveguide device fabrication is probably the most widely studied application of femtosecond laser micromachining in transparent dielectrics at the present time. Devices such as buried waveguides, power splitters, couplers, gratings, optical amplifiers and laser oscillators have all been demonstrated. This paper reviews the application of the femtosecond laser direct‐write technique to the fabrication of active waveguide devices in bulk glass materials.     

Wet-chemical treatment and electronic interface properties of silicon solar cell substrates

On textured n-type silicon substrates for solar cell manufacturing, the relation between light trapping behavior, structural imperfections, energetic distribution of interface state densities and interface recombination losses were investigated by applying surface sensitive techniques. The field-modulated surface photovoltage (SPV), in-situ photoluminescence (PL) measurements, total hemispherical UV-NIR-reflectance measurements and electron microscopy (SEM) were employed to yield detailed information on the influence of wet-chemical treatments on preparation induced micro-roughness and electronic properties of polished and textured silicon substrates. It was shown that isotropic as well as anisotropic etching of light trapping structures result in high surface micro-roughness and density of interface states. Removing damaged surface layers in the nm range by wet-chemical treatments, the density of these states and the related interface recombination loss can be reduced. In-situ PL measurements were applied to optimise HF-treatment times aimed at undamaged, oxide-free and hydrogen-terminated substrate surfaces as starting material for subsequent solar cell preparations.      

Optical design of bent rib waveguide with MOS cross-section

We provided a single-mode bent MOS-cross-section rib waveguide design with 0.9 dB/cm bending loss at 25 μm bending radius. The peak position for the TE-like mode was tuned to the gate oxide around which the maximum amount of free carriers are accumulated to optimize the free carrier dispersion effect.