Real-Time monitoring of III-V molecular beam epitaxial growth using spectroscopic ellipsometry

We report the real-time monitoring of monolayer thickness changes in AlAs and GaAs layer growth on rotating GaAs substrates using spectroscopic ellipsometry (SE). A phase-modulated spectroscopic ellipsometer was integrated with a III-V MBE system by triggering spectral acquisition synchronously with substrate rotation. Absolute thickness accuracy was verified using ex situ SE measurement. Reasonable agreement was also obtained between in situ growth rate measurements by SE and reflection high energy electron diffraction. The precision and speed of this method appears suitable for real-time control of quantum devices, such as resonant-tunneling diodes.     

A study of Si-L and O-K ELNES in plant material: SiO2, Ca- and Zn-silicate in Minuartia

The formation of vacuolar precipitates containing silicon and calcium, as well as the accumulation of metal-silicates in cell walls of Minuartia has been investigated by electron microscopy, energy-dispersive X-ray analysis and electron spectroscopic imaging. The bond state of the elements concerned is examined by analysing energy-loss near-edge structures (ELNES), particularly the Si-L_2,3 and the O-K ELNES. Experimental ELNES results are compared with local densities of unoccupied states calculated by molecular orbital methods and results of XANES calculations.     

可调谐激光晶体的成分,结构和激光性质

本文分析可调谐激光晶体的激光性质同基质成分和晶体结构的关系。晶体内过渡金属离子的吸收和辐射光谱特性主要由离子的价态、基质格位多面体类型和晶场强度决定。晶场强度受基质成分和结构的强烈影响,如氟化物与氧化物差别大;被置换离子的半径,其它离子等均有影响。本文还讨论离子变价、杂质、格位对称性对激光性能的影响。     

Ellipsometry of Liquid Helium Films on Gold, Cesium, and Graphite

We have developed a modulated null ellipsometer with sub-monolayer resolution to measure adsorbed liquid helium thin films at temperatures below 4 K. Adsorption isotherms of ⁴He on gold, cesium, and graphite are presented. For Au and Cs substrates, the reflecting surface for our ellipsometric measurements is the metallic electrode of a quartz crystal microbalance(QCM). Performing both types of measurements simultaneously on the same substrate provides a direct method of converting the ellipsometric signal into an absolute film thickness without constructing a detailed model of the refractive index of the substrate. Isotherms on gold above and below T¸ show that the ellipsometric signal is unaffected by the superfluid transition; the ellipsometer measures the total film thickness independent of the superfluid fraction. Isotherms on cesium above the wetting temperature show a prewetting step. Isotherms on clean graphite show steps due to layering.     

生物芯片测试方法进展

生物芯片技术近年迅速发展 ,其中信号检测是生物芯片一个重要的相关技术。分别简要地介绍了集成半导体荧光测试 ,基于二元光学的荧光测试 ,利用椭圆偏振测量仪原理测试等生物芯片的检测方法 ,对测试技术进行了评述     

碱土金属氧化物对掺铒磷酸盐玻璃光谱性质的影响

以摩尔组成为72P2O5-8Al2O3-20RO(R=Mg,Ca,Sr,Ba)和(77-x)P2O5-8Al2O3-(15 x)BaO(x=0,5,10,15,20)掺铒磷酸盐玻璃系统为研究对象,测量和计算了掺铒磷酸盐玻璃的各种光谱参数,探讨了不同网络修饰体及其含量对掺铒磷酸盐玻璃光谱性质的影响。结果表明：玻璃折射率nd、积分吸收截面∑sbs发射截面σemi,J-O强度参量Ωt以及自发辐射几率AR都有较强的成分依赖性,主要决定于Er^3 离子周围结构和Er-O键共价性的变化;减小Er-O键的共价性可得到较高的∑abs,σemi以及AR。     

掺铒钨碲酸盐玻璃光谱性质的研究

研究了掺铒钨碲酸盐玻璃的吸收光谱和荧光光谱。应用JuddOfelt理论计算了Er3+的光谱强度参数Ωt(t=2,4,6)、自发辐射跃迁几率、荧光分支比和辐射寿命。从光谱强度参数的计算说明掺铒钨碲酸盐玻璃中Er—O键的共价性强于碲酸盐玻璃中Er—O键的共价性。玻璃的荧光半高宽为52nm,大于Er3+在磷酸盐和硅酸盐玻璃中的荧光半高宽。应用McCumber理论,计算了钨碲酸盐玻璃中Er3+离子在峰值波长1532nm的受激发射截面,为0.91×10-20cm2,大于Er3+在碲酸盐玻璃中的受激发射截面0.75×10-20cm2。由于掺铒钨碲酸盐玻璃的玻璃转变温度高、有较大的声子能量、较宽的荧光半高宽和较大的受激发射截面,是制作高增益的光波导放大器的理想材料。     

真假百元人民币的拉曼光谱研究

采用拉曼光谱作为分析手段,以近红外激光785 nm波长激发,获得了真、假一百元人民币在固定人像水印、全息开窗安伞线、隐形面额数字和光变油墨数字等处的谱图.发现真币与假币的谱图有明显差别,而且不同来源的假币的拉曼光谱也存在着可分辨的差异.研究表明,利用拉曼光谱的分子指纹和微区分析能力,不仅对伪造、变造人民币的识别有重要价值,而且可以分辨不同来源的假币.     

ZrO2/SiO2双层膜膜间渗透行为初步研究

用溶胶-凝胶技术,采用提拉镀膜法在K9玻璃基片上镀制了ZrO2/SiO2双层膜和SiO2/ZrO2双层膜,研究了这两种膜层之间的渗透问题。用X射线光电子能谱仪(XPS)测量了薄膜的成分随深度方向的变化,用反射式椭偏仪对X射线光电子能谱仪测得的实验结果进行模拟与验证。结果表明,用X射线光电子能谱仪测得的实验结果建立的椭偏模型,模拟出来的椭偏曲线和用椭偏仪测量出来的椭偏曲线十分吻合;对于ZrO2/SiO2双层薄膜,膜层间的渗透情况不是很严重,在薄膜界面处薄膜的成分比变化非常明显,到达一定深度后薄膜的成分不再随深度的变化而变化;SiO2/ZrO2双层膜膜层界面间的渗透十分严重,渗透层的深度比较大,底层几乎发生了完全渗透。     

直流磁控溅射制备a-Si:H膜工艺及其在激光器腔面膜上的应用

利用直流(DC)磁控溅射方法制备氢化非晶硅(a-Si∶H)薄膜。研究了氢气流量、溅射源功率对膜的沉积速率、氢含量(CH)以及光学性能的影响。通过傅里叶变换红外(FTIR)吸收光谱计算氢含量,其最大原子数分数为11%。用椭偏仪测量了膜的折射率n和消光系数k,发现a-Si∶H薄膜的k值和n值都随CH的增加而减小。将优化的实验结果用于半导体激光器腔面高反镜的镀制,a-Si∶H薄膜在808 nm波长处的n和k分别为3.2和8×10-3,获得了良好的激光输出特性。