纳米二氧化钒薄膜的制备及红外光学性能

采用双离子束溅射方法在Si_3N_4/SiO_2/Si基底表面沉积氧化钒薄膜,在氮气气氛下热处理获得二氧化钒薄膜.利用x射线衍射(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了热处理温度对氧化钒薄膜晶体结构、表面形貌和组分的影响,利用傅里叶变换红外光谱(FT-IR)对二氧化钒薄膜的红外透射性能进行了测试分析.结果表明,所制备的氧化钒薄膜以非晶态V_2O_5;和四方金红石结构VO_2为主,经400℃、2 h热处理后获得了(011)择优取向的单斜金红石结构纳米VO_2薄膜,提高热处理温度至450℃,纳米结构VO_2薄膜的晶粒尺寸减小.FT-IR结果显示,纳米VO_2薄膜透射率对比因子超过0.99,高温关闭状态下透射率接近0.小晶粒尺寸纳米VO_2:薄膜更适合在热光开关器件领域应用.

基于仿生模式识别的DOA估计方法

该文就仿生模式识别(拓扑模式识别)在非感性抽象对象的信息处理方面的应用作了一些探索,提出了一种基于仿生模式识别的DOA估计方法.这种方法的建模过程是用在实际环境下采集的训练样本构造人工神经网络模型,对环境的适应能力较强,且这种方法的计算量较小,可以实现系统实时处理.实验结果表明:在信噪比为20 dB和0 dB时,该方法的正确估计率可达100%;在信噪比降为-20 dB时,该方法仍有83%的可识别率.

Si被注入Gd后的磁性及其整流特性的研究

采用离子束技术,在n型硅基片中注入稀土元素钆,制备了磁性-非磁性p-n结.磁性层Gd_xSi_(1-x)表现出优良的磁学性能,高居里温度,高原子磁矩(利用RKKY模型可以得到解释),低矫顽力,并保持着半导体的属性,磁性-非磁性p-n结具有整流特性,但没有观察到明显的磁电阻效应.

Study of He-induced nano-cavities as sinks of oxygen for forming silicon-on-insulator

In the present work, a Cz-Silicon wafer is implanted with helium ions to produce a buried porous layer, and then thermally annealed in a dry oxygen atmosphere to make oxygen transport into the cavities. The formation of the buried oxide layer in the case of internal oxidation (ITOX) of the buried porous layer of cavities in the silicon sample is studied by positron beam annihilation (PBA). The cavities are formed by 15 keV He implantation at a fluence of 2 x 10(16) cm(-2) and followed by thermal annealing at 673 K for 30 min in vacuum. The internal oxidation is carried out at temperatures ranging from 1073 to 1473 K for 2 h in a dry oxygen atmosphere. The layered structures evolved in the silicon are detected by using the PBA and the thicknesses of their layers and nature are also investigated. It is found that rather high temperatures must be chosen to establish a sufficient flux of oxygen into the cavity layer. On the other hand high temperatures lead to coarsening the cavities and removing the cavity layer finally.

Structural and optical properties of 6H-SiC helium-implanted at 600 K

Single crystals of 6H-SiC were implanted at 600 K with 100 key He ions to three successively fluences and subsequently annealed at different temperatures ranging from 873 to 1473 K in vacuum. The recovery of lattice damage was investigated by different techniques including Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy and Fourier transform infrared spectroscopy. All three techniques showed that the damage induced by helium ion implantation in the lattice is closely related to the fluence. Rutherford backscattering spectrometry/channeling data on high temperature implantations suggest that for a fluence of 3 x 10(16) He+/cm(2), extended defects are created by thermal annealing to 1473 K. Apart from a well-known intensity decrease of scattering peaks in Raman spectroscopy it was found that the absorbance peak in Fourier transform infrared spectroscopy due to the stretching vibration of Si-C bond shifted to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with increasing annealing temperature. These phenomena are attributed to different lattice damage behavior induced by the hot implantation process, in which simultaneous recovery was prevailing. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis of carbon nanotube bundles with mesoporous structure by a self-assembly solvothermal route

A kind of carbon nanotube bundle has been synthesized by a simple one-step solvothermal reaction between Na and hexachlorobenzene (HCB) using NiCl2 as catalyst precursor. Before the reaction, NiCl2 was initially dispersed ultrasonically in cyclohexane then prereduced by Na at 230degreesC to produce small Ni particles in reduced state. The tubes thus-produced have a uniform outer diameter of about 20 nm, an inner diameter of 4 nm, and are highly ordered assembled as bundles which have a 2D hexagonal arrangement as proven by SAXS and TEM experiments.