Micro-Raman study on hydrogenated protocrystalline silicon films

Good quality hydrogenated protocrystalline silicon films were successfully prepared by radio frequency plasma enhanced chemical vapor deposition (PECVD) with various hydrogen dilution ratios (R = ([H-2]/[SiH4]) from 10 to 100). The photosensitivity of the films is up to 10(6) under the light intensity of 50mW.cm(-2). The microstructure of the films was studied by micro-region Raman scattering spectra at room temperature. The deconvolution of the Raman spectra by Gaussion functions shows that the films deposited under low hydrogen dilution ratios (R < 33) exhibit typical amorphous properties, while the films deposited under high hydrogen dilution ratios (R > 50) possess a diphasic structure, with increasing crystalline volume fraction with R. The size of the crystallites in the diphasic films is about 2.4 mm, which was deduced from the phonon confinement model. The intermediate range order of the silicon film increases with increasing hydrogen dilution ratio.

A silicon capacitive microphone based on oxidized porous silicon sacrificial technology

In this paper, a new capacitive microphone fabrication technology is proposed. It describes using the oxidized porous silicon sacrificial technology to make air gap and using KOH etching technique to make the backplate containing acoustic holes based on the principle that the heavy p(+)-doping silicon can be nearly etched in KOH solution. The innovation of the method is using oxidized porous silicon technology. The sensitivity of the fabricated microphone is from -55dB ( 1.78mV/Pa) to -45dB (5.6mV/Pa) in the frequency range of 500Hz to 25kHz. Its cut-off frequency is higher than 20kHz.

基于代码覆盖的恶意代码多路径分析方法

传统的恶意代码动态分析每次分析的对象只是恶意代码的某一个执行路径,难以保证分析的全面性.恶意代码多路径分析是解决该问题的思路之一.本文提出一种基于代码覆盖的多路径分析方法,通过标识判断条件节点,减少局部路径被重复遍历的次数,在保证分析效果的同时,提高分析系统的分析效率以及代码覆盖率.通过对大量典型恶意代码的分析验证表明,本方法可明显缩短分析时间,提高分析效率和分析的全面性.

基于进程行为的异常检测模型

利用系统漏洞实施攻击是目前计算机安全面临的主要威胁.本文提出了一种基于进程行为的异常检测模型.该模型引入了基于向量空间的相似度计算算法和反向进程频率等概念,区分了不同系统调用对定义正常行为的不同作用,提高了正常行为定义的准确性;该模型的检测算法针对入侵造成异常的局部性特点,采用了局部分析算法,降低了误报率.

面向无线射频识别应用的复合订阅匹配

传统的发布/订阅系统不支持具有丰富时序关系的复合事件,不能很好地满足无线射频识别应用的需要。针对无线射频识别应用的特点,设计了面向无线射频识别应用的复合订阅语言,研究了订阅语言的组成和使用,基于时间事件、复合订阅的匹配图表示、事件检测的消费语义,给出了相应的复合订阅匹配算法。该算法已在OncePubSub系统中实现,并与Siena改造版J、ESS改造版进行了性能比较。

非线性放大环形镜“8”字腔光纤激光器实验研究

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注入噪声对光纤激光器锁模启动的影响

国家自然科学基金资助课题(60537060)

Exact description of a cylindrically symmetrical complex-argument Laguerre-Gauss beam

Based on the perturbative series representation of a complex-source-point spherical wave an expression for cylindrically symmetrical complex-argument Laguerre-Gauss beams of radial order n is derived. This description acquires the accuracy up to any order of diffraction angle, and its first three corrected terms are in accordance with those given by Seshadri [Opt. Lett. 27, 1872 (2002)] based on the virtual source method. Numerical results show that on the beam axis the number of orders of nonvanishing nonparaxial corrections is equal to n. Meanwhile a higher radial mode number n leads to a smaller convergent domain of radius. (C) 2008 Optical Society of America.

表面处理对p-GaN欧姆接触的影响

分别用稀盐酸、王水以及(NH_4)_2S溶液处理p-GaN表面,通过测试样品表面Ols的X射线光电子能谱(XPS),比较了这些溶液去除p-GaN表面氧化层的能力;在经不同溶液处理后的样品表面,以相同的条件制作Ni/Au电极,并测试其与p-GaN的比接触电阻,结果表明经稀盐酸处理后的样品表面,由于其氧含量较高,不能与Ni/Au形成良好的欧姆接触,而经王水和(NH_4)_2S溶液处理后的p-GaN表面,能与Ni/Au形成良好的欧姆接触;最后,通过比较样品表面的Ga/N原子浓度比,探讨了王水处理p-GaN表面能够形成良好欧姆接触的原因.

非晶/微晶过渡区域硅薄膜的微区喇曼散射研究

通过改变氢气对硅烷气体的稀释程度，并保持其他的沉积参量不变，用等离子体增强化学气相沉积（PECVD）方法成功地制备出非晶/微晶相变过渡区域的硅薄膜样品。测量了样品的室温光电导和暗电导，样品的光电性能优越，在50 mW·cm~（-2）的白光照射下，光电导和暗电导的比值达到10~6。在室温下用微区喇曼谱研究了薄膜的微结构特性，用高斯函数对喇曼谱进行了拟合分析。结果表明，在我们的样品制备条件下，当H_2和SiH_4的流量比R较小时，样品表现出典型的非晶硅薄膜 的结构特性；随流量比R的增大，薄膜表现出两相结构，其中的微晶成分随氢稀释比的增大逐渐增多；用量子尺寸效应估算了两个高氢稀释样品（R > 50）中微晶粒子的平均尺寸大小为2.4 nm左右；样品的中程有序度随氢稀释程度的增加而增大。