Metal-particle-induced, highly localized site-specific etching of Si and formation of single-crystalline Si nanowires in aqueous fluoride solution

A straightforward metal-particle-induced, highly localized site-specific corrosion-like mechanism was proposed for the formation of aligned silicon-nanowire arrays on silicon in aqueous HF/AgNO3 solution on the basis of convincing experimental results. The etching process features weak dependence on the doping of the silicon wafers and, thus, provides an efficient method to prepare silicon nanowires with desirable doping characteristics. The novel electrochemical properties between silicon and active noble metals should be useful for preparing novel silicon nanostructures and also new optoelectronic devices.     

电沉积种子层化学控制生长氧化锌纳米棒和纳米管

采用水溶液法在电沉积的ZnO种子层上制备了高度取向的ZnO纳米棒阵列,并通过碱溶液化学腐蚀法获得了ZnO纳米管。对ZnO纳米棒和纳米管的溶液生长和腐蚀过程进行了分析。结果表明,种子层的结构和性能对ZnO纳米棒有着重要的影响,在-700 mV电位下沉积的种子层薄膜均匀性好,生长的纳米棒密度大、与基底垂直性好;碱溶液对纳米棒的腐蚀具有选择性,通过控制腐蚀液的浓度和时间,可获得中空的ZnO纳米管。     

非晶熔石英表面等离子体刻蚀过程 中的表面晶化研究

本工作采用电子回旋共振(ECR)低压等离子体刻蚀技术, 刻蚀非晶熔石英表面. Ar/CF₄为反应气体刻蚀后再经O等离子体钝化, 非晶熔石英表面出现晶化现象. 晶化层约几百纳米厚. Ar/CF₄在ECR的电磁场作用下产生F离子与C离子, F离子使熔石英表面的Si-O共价键断裂, 并释放出O离子. C离子与O离子迅速键合生成CO₂, 而被断键的Si原子与四个F原子键合生成气态SiF₄. 熔石英原始表面被去除的同时, 在新的表面留下大量不饱和Si原子. 不饱和Si原子在高温条件下被O等离子钝化, 形成结晶态α 方石英.     

随机稀释基底上刻蚀模型动力学标度行为的数值模拟研究

表面界面动力学粗化过程是凝聚态物理领域重要的研究内容,为研究基底不完整性对刻蚀模型动力学 标度行为的影响,本文采用Kinetic Monte Carlo(KMC)方法,分析研究了在随机稀释基底上刻蚀模型(Etching model)生长表面的动力学标度行为.研究发现:尽管随机稀释基底的不完整性会对刻蚀表面的动力学 行为产生显著的影响,导致刻蚀表面粗糙度指数和生长指数有明显的增加, 但其仍基本满足原有的动力学标度规律.此外,本文还对刻蚀表面动力学标度指数的有限尺寸效应进行了 分析讨论.     

Enhanced physical properties of porous silicon for improved hydrogen gas sensing

In the current communication, porous silicon samples were prepared by pulsed photoelectrochemical etching using a hydrofluoric acid-based solution. The structural and gas-sensing properties of the samples were studied. Apart from the cycle time T and pause time T_off of the pulsed current, a novel parameter, in the shape of the current named ‘delay time T_d’ was introduced. Our results showed that by optimization of delay time, the porosity of samples can be controlled due to the chemical preparation of silicon surface prior to electrochemical anodization. The fourier-transform infrared measurements of porous silicon (PS) layers on Si substrate showed that the typical PS surface was characterized by chemical species like Si–H and Si–O–Si terminations. The two-minute delay before applying electrical current was considered sufficient for the fabrication of higher porosity (83%), more uniform, and more stable structures. The photoluminescence (PL) peak of the optimized sample showed higher intensity than the other samples. An obvious PL blue shift also revealed a change in the crystallographic characteristics of silicon due to quantum confinement effects. Metal–semiconductor–metal diodes with Schottky contacts of nickel were fabricated on PS samples and the potential application of optimized substrates for the improved sensitivity, stability, response time and recovery time of hydrogen gas sensors was subsequently studied.     

树形结构Si/ZnO纳米线阵列的制备及光学性能

用一种低成本的方法制备出了树形结构Si/ZnO纳米线阵列。首先在室温条件下用金属辅助化学腐蚀法在Si(100)衬底上制备了Si纳米线阵列,Si纳米线的直径尺寸及分布都很均匀,通过改变腐蚀时间,能够得到高度不同的Si纳米线阵列。利用磁控溅射在Si纳米线表面制备一层ZnO薄膜,然后利用水热法在Si纳米线阵列上生长了ZnO纳米线。通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和光致发光(PL)测试对样品进行了表征。通过这种方法制备的Si/ZnO复合结构在太阳能电池、光催化等领域有潜在应用价值。     

湿法和溶脱法的亚微米ZnO:Al光栅制备

以激光干涉法得到的光刻胶图案为掩模,采用湿法刻蚀和溶脱-剥离法制备了具有良好减反射特性的亚微米掺铝氧化锌（ZnO:Al, AZO）光栅。表面形貌特征和反射光谱测试结果表明,湿法刻蚀较溶脱-剥离法得到的AZO光栅表面更为粗糙,两者均方根粗糙度分别为25.4,7.6 nm。在400～900 nm波段,两种方法制备的周期和高度相同的光栅,平均总反射率分别由AZO薄膜的12.5%下降到8.3%和10.2%。两者的平均镜面反射率分别为6.2%和6.6%,平均漫反射率分别为2.1%和3.6%。湿法刻蚀得到的表面较为粗糙AZO光栅的漫反射明显减弱,从而导致总的减反特性优于溶脱-剥离法得到的表面起伏相对较小的AZO光栅。     

Investigations of impurity striations in potassium bichromate crystals

Impurity striations in potassium bichromate crystals (KBC, lopezite) formed during crystal growth from aqueous solution were revealed by chemical etching and analyzed. Striations were revealed as etch grooves, as rows of dislocation etch pits and as rows of flat‐bottomed etch pits. Various types and groups of striations have been visualized. Some striations were due to lateral segregation of impurities caused by convection flow of the mother solution, other were formed during growth stoppages whereas induced striations were generated by changes in hydrodynamical conditions. Growth rates changes resulted in zonal distribution of impurities, formation of planar lattice strain, rows of clusters of point defects and rows of dislocations. Generation of striations with different intensities in various sectors is a proof of the selective capture of impurities. Ratios of growth rates of various faces of KBC crystals growing in forced and free convection regimes were determined by induced striations. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一类特殊的对称的块循环矩阵的特征值

In this paper, the spectrum and characteristic polynomial for a special kind of symmetric block circulant matrices are given.     

Microwave-assisted acid-induced formation of linker vacancies within Zr-based metal organic frameworks with enhanced heterogeneous catalysis

Herein,we report a microwave-assisted acid-induced post-treatment method for the formation of linker vacancies within Zr-based metal organic frameworks(Zr-MOFs).The number of linker vacancies can be easily regulated with this method by changing the concentration of the HCl solution and the duration of microwave irradiation.The optimized defective UiO-66 showed higher linker defects with a higher specific surface area and thermal stability.The results of the catalytic cyclization of citronella showed that the Zr-MOFs with more defects exhibited enhanced catalytic performance.This work may provide a new method for the creation of defective MOFs with high activity and stability.