Continuous in situ growth rate extraction using pyrometric interferometry and laser reflectance measurement during molecular beam epitaxy

We describe a new, universal, and easy-to-use method for real-time thickness and growth rate extraction based on in situ optical monitoring during molecular beam epitaxy of GaAs/AlAs layered structures. The method is based on a novel least-square phase extraction algorithm and a model-reference comparison scheme. The new method demonstrates a significantly reduced growth rate estimation error (<2%) on both pyrometric interferometry (PI) and laser reflectance (LR) monitored data over conventional methods. Based on preliminary studies, the new method also shows excellent dynamic tracking of growth rate with a thickness resolution of only 30 nm when the growth rate is intentionally changed.     

Implementation of a closed-loop growth scheme for AlAs-GaAs distributed Bragg reflector (DBR) structures using in situ pyrometric interferometry monitoring

We have investigated a closed-loop control system for molecular beam epitaxial growth of quarter-wavelength AlAs-GaAs distributed Bragg reflector (DBR) structures using in situ pyrometric interferometry. The quasi-sinusoidal PI data was being treated as an amplitude and phase modulated signal for control of layer thickness. Highly reproducible PI signals were obtained without the need of careful growth rate calibration. This technique can be useful in achieving reproducible growth of DBR structures, including vertical cavity surface emitting lasers.     

用激光干涉法实时监控同轴磁控溅射ZnO薄膜的厚度

本文介绍了一种在我所生产的TCJ-300型同轴磁控溅射设备上采用激光实时监控ZnO薄膜厚度的方法.实验结果表明,该方法与其它膜厚监控方法相比较具有多种优点:它可以在溅射过程中实时显示薄膜的厚度、均匀性和溅射速率等;本实验装置简单;操作方便;其监控精度优于1.5%.     

Measurement of thin liquid film thickness in pipes based on optical interferometry

Accurate measurement of the thin liquid film thickness in pipes is the foundation for studying the characteristics of the film. In this paper, an interferometry-based measurement of liquid film thickness in transparent pipes is developed, which can greatly improve the accuracy, extend the lower limit of measurement and provide a new technical approach for the calibration and traceability. The light intensity distribution is established based on the optical path analysis and a mathematical model....     

High-capacity optical storage using multiple wavelengths, multiplelayers and volume holograms

A system is proposed that combines both the multilayer storage and the wavelength multiplexing afforded by using volume holograms to enhance by several fold the optical data storage capacity of compact discs. The storage capacity and interchannel crosstalk are analysed as functions of data-channel wavelength separation and reading beam spot size. A storage capacity of 9.7 Gbyte per disc is provided when six layers and six wavelengths are used     

紧凑型光谱薄膜测厚仪的研制

为了开发一种用于测量各向同性均匀薄膜介质厚度的紧凑型薄膜测厚仪,采用了共光路垂直入射设计,利用薄膜干涉原理,通过非线性优化算法对反射光谱进行了拟合,反演计算出了薄膜样品的厚度。采用该仪器测量部分SiO2/Si薄膜样件,测量结果与商业椭偏仪测量结果之间的相对偏差小于0.5%,而单次测量时间仅为70ms。结果表明,该薄膜测厚仪具有对测量距离不敏感、光路简洁、结构紧凑及重复性精度良好等优点,对实现在线实时测量功能具有积极意义。     

Fixed-angle, energy-dispersive x-ray reflectivity measurement of thin tantalum film thickness

In this work, we employed a fixed-angle, energy-dispersive x-ray reflectivity technique to obtain the thickness of thin tantalum films (examples <9 nm) within seconds using a conventional, low-energy x-ray copper or chromium source (20 kV/20 mA/400 W). We compared this fixed-angle, energy-dispersive result with more conventional fixed-energy (monochromatic source), angular-dispersive x-ray reflectivity to establish the validity of the energy-dispersive method. This x-ray technique may be particularly useful for the metrology of growing thin-barrier layers, atomic-layer passivation, and seed-layer measurements in future microelectronics applications. Currently, thickness precision is limited by modeling assumptions and the energy discrimination available from x-ray detectors.     

In vitro simultaneous measurement of refractive index and thickness of biological tissue by the low coherence interferometry

We proposed and demonstrated in vitro simultaneous measurement of refractive index and thickness of biological tissue. The technique is based on the low coherence interferometry combined with precise translation stages. Refractive indices were determined with the accuracy of less than 1% for tissue samples of a few hundred micron thickness, including chicken tissue, human tooth and nail. Simultaneous measurement of refractive index and thickness of multilayer tissue are also demonstrated.     

温度应变双参量同时测量的光纤传感技术研究

光纤光栅用于传感领域存在应变和温度的交叉敏感问题。从温度与应变的分离方法方面主要分双波长矩阵法和双参量矩阵法两类,综述了用于温度和应变同时测量的光纤光栅传感器的最新研究成果,对一些基于其他理论的新方法也做了简要的介绍。概括了各方法的基本原理,并对这些方案的优点和不足进行了分析。     

电子散斑相位检测的滤波方法研究

本文提出空域中值迭代滤波方法和频域离散余弦变换滤波方法,利用三步相移技术成功实现相位检测.对两种方法所得结果进行了比较.实验结果表明这两种方法对ESPI条纹图像进行处理是有效的.     

Hg1-xCdxTe/CdTe/Si薄膜厚度测试方法的研究

在分子束外延生长高质量的CdTe/Si复合衬底上,分别通过MBE和LPE技术成功地研制出Hg1-xCdxTe/CdTe/Si红外探测器所需的重要红外半导体材料。利用傅里叶变换红外光谱仪对Hg1-xCdxTe/CdTe/Si红外半导体材料的红外透射光谱进行测试分析且计算薄膜厚度,并配合扫描电子显微镜对其厚度计算分析进行校正,最终获得一种无破坏、无污染、快捷方便的多层膜厚度测试方法。     

热镀锌带钢湿膜厚度在线测量系统的研究

钝化膜厚度的在线测量可为热镀锌带钢生产过程中的涂膜厚度控制提供客观指导.介绍了热镀锌带钢钝化膜厚度在线测量的重要意义,描述了近红外测厚仪的工作原理,并重点研究了一种由近红外测厚仪、接口单元和PC机组成的热镀锌带钢钝化膜湿膜厚度在线测量系统,包括该系统各组成部分的功能和应用效果.     

基于PVDF压电薄膜的超声波测厚技术探究

开展了基于PVDF压电薄膜的超声波测厚技术研究,通过分析超声波是弹性机械波的一种,在同种均匀介质中,其传播声速一定,当从一种介质进入另一种介质时,在结构表面会发生反射作用。因此,我们可以认为超声波从被测试件的表面发出到接收到另一底面反射波信号的传播间隔时间与被测厚度值成正比关系,从而测量厚度的问题转化成测量超声波在试件中传播时间的问题。基于PVDF压电薄膜的超声波测厚技术将为快速便捷的测量厚度问题提供一种新的手段,并为将来测厚技术系统的开发奠定技术基础,具有工程应用价值。     

光热辐射技术测量钴涂层热学参数及厚度

为获得涂层材料特性,使用光热辐射(PTR)技术进行无损检测,并提出一种基于一维 三层PTR 理论模型的标定方法,完成了对Al基体钴涂层热学参数、厚度及分布的检测。三层PTR 理论模型,由涂层、 空气缺陷层和基体组成。搭建了实验平台,对两种不同厚度的钴(Co)涂层Al基体样品、无涂 层Al基体参考样品 进行了多点PTR测量。利用参考样品对带涂层样品PTR相位信号进行规格化,以消除检 测系统的影响。 通过多参数优化算法,对规格化后相位信号进行拟合,完成三层理论模型公式热参数的标定 ,求出了涂层 材料的热传导率和热扩散系数,进而计算得到各检测点涂层厚度及分布。实 验结果验证了理论 模型的正确性,以及材料作为基体和涂层时其热学性能的值会发生改变。     

Optical measurement of silicon membrane and beam thickness using areflectance spectrometer

An optical technique for measuring the thickness of silicon membranes and beams such as those used in micromechanical devices is presented. The measurement, based on reflectance spectrometry, is rapid and nondestructive. The reflectance-spectrometry technique can be used to measure silicon membrane thickness in the range from 0.1 to 5 μm     

Anisotropic magnetoresistance of the epitaxial single-crystal Fe(001) film of nanoscale thickness

The dependence of the anisotropic magnetoresistance (AMS) of the single-crystal Fe(001) film grown with the aid of the pulsed laser evaporation on the direction and magnitude of the external magnetic field is analyzed. Three ranges of magnetic fields with different types of variation in AMS with the direction of magnetic field are revealed. The discontinuities of resistance and the hysteresis are demonstrated in a certain range of magnetic fields. The anisotropy field is estimated using the experimental results.     

Simultaneous displacement measurement method of multiple targets based on laser self-mixing interference

In order to simultaneously measure the displacements of multiple targets, the laser self-mixing interference(SMI) measurement method based on variational mode decomposition(VMD) is proposed. The SMI signal containing the motion information of the external targets is detected by a photodiode. The VMD can non-recursively decompose the mixed SMI signal into SMI signals corresponding to different external targets. The displacement signals can be reconstructed by fringe counting method and interpolation method. The experimental results show that the displacement signals of different external targets can be reconstructed with half wavelength accuracy, which verifies the correctness and feasibility of this method. This method can improve the measurement efficiency, which offers an effective method for the multi-channel displacement measurement.     

基于LPFG和HBF环镜的温度和应变同时测量

利用长周期光纤光栅（LPFG）和高双折射光纤（HBF）环镜的谐振波长对温度和应变的灵敏度差异,设计了温度和应变同时区分测量系统。在理论分析的基础上,分别测定了LPFG以及HBF环镜谐振波长对温度和应变的灵敏度系数,构建相关系数矩阵方程,实现温度和应变区分测量。实验测得该系统的温度和应变测量精度分别为±0.36℃和±13...