椭偏法测量表面微粗糙合金钢材料的光学常数研究

采用椭偏法测量入射光波长为0.632μm,入射角为50°～85°时合金钢的光学常数。考虑材料表面的粗糙度,用Ohlidal-Lukes理论对所测光学常数值进行了修正,发现椭偏参量的修正量随入射角增大而增大。结果表明,测量入射角在50°～70°范围内测量值与修正后计算结果基本一致,在70°～85°范围内测量值与修正后的计算结果差距较大。因此,用椭偏法测量合金钢光学常数时使入射角小于70°,测量结果会更加准确。     

合金钢材料光学常数的椭偏测量及其修正

用椭偏法测量了入射光波长0.632μm、入射角50°至85°时某合金钢的光学常数。考虑材料表面的粗糙度,用Ohlidal-Lukes理论对所测光学常数值进行修正,发现椭偏参量的修正量随入射角增大而增大。结果表明,用椭偏法测量合金钢光学常数时采用较小入射角能获得更精确的样片光学常数。     

椭圆偏振光谱中的主角测量条件分析

对椭圆偏振光谱中的主角测量条件进行了分析。当入射角等于主角 θp 时 ,椭偏参数的相位为 90°,据此给出了当材料的介电函数已知时对θp 进行数值和解析计算的公式和方法 ,并可相应地计算出椭偏参数的幅值 ρp0 。在θp 入射角下测量可获得较高的数据精度。主角条件下椭偏参数 ρp0 及其相位Δp 的实验测量结果与计算值符合得很好。本工作给出的计算公式和方法可在其他光谱实验中获得应用。     

正入射全自动扫描反射率绝对值光谱仪的研制

采用Ｍ型棱镜分光束法研制了一台全自动扫描绝对反射率光谱仪，测量光谱范围为３５０ｎｍ～８２０ｎｍ（１．５～３．５ｅＶ），样品入射角为５°，测量和数据采集处理全过程由计算机控制．测量绝对值精度优于±１％，测量重复性优于０．１％．采用本谱仪对热蒸发金膜和（１１１）锗本征体单晶进行测量，获得了与椭偏测量以及文献报道相一致的结果．     

双菱体λ/4消色差相位延迟器的设计

根据菲涅尔全内反射相变理论,给出了双菱体λ/4消色差器的结构设计、性能分析和测量方法.由有效通光孔径和光线追迹设计出BK7玻璃在波长532 nm时相位延迟λ/4的双菱体的结构,用作532 nm至1 064 nm波长范围的标准λ/4相位延迟器.理论分析了入射角变化和波长变化对双菱体相位延迟的影响,当入射角变化限制在±4.3°以内时,其影响得到补偿;波长从532 nm到1 064 nm产生的误差为－0.65°.采用椭偏法中的消光技术,分别实测了双菱体在532 nm和1 064 nm波长下的相位延迟为：90.08±0.14°和88.99±0.1°,可知两不同波长产生的相位延迟误差为－1.09°.     

一种同时测量平行偏差、倾斜偏差的方法

提出了一种仅由接收物镜和CCD构成的接收器,通过物镜位置的调整,可以同时完成平行偏差（平偏）和倾斜偏差（角偏）这两个参量的测量.通过对系统像差的分析,提出了可显著降低物镜像差对测量结果影响的算法.理论和实验数据表明,对于平偏测量范围为±10 mm、角偏测量范围为±2°、接收物镜焦距为50 mm、CCD尺寸为1/1.6 inch的系统,平偏测量准确度可达0.02 mm,角偏测量准确度可达9.5″.     

纳米厚度薄膜外差椭偏测量技术的研究

结合激光外差干涉法和透射式椭偏测量原理,研究了一种快速、高精度测量纳米厚度薄膜光学参数的方法。计算并分析了复灵敏度因子随薄膜参数和入射角度的变化规律、椭偏参数的选择及容许测量误差。两个声光调制器产生20kHz的拍频,采用简单的直接比相方法即可获得优于0.1°的相位分辨率,而且测量系统中没有使用任何波片和运动部件,抗干扰能力强且测量过程完全自动化,适用于工业现场在线连续测量。实验数据和理论分析表明,此方法可以达到亚纳米级测量精度。     

椭偏光谱测量中椭偏参数的灵敏度分析

在对椭圆偏振测量的基本原理进行了简单介绍和推导后,讨论了椭圆偏振测量中椭偏参数关于薄膜参数的灵敏度以及入射角对椭偏参数的影响,并进行了具体的仿真分析,得到如下结论：椭偏参数Delta对薄膜光学常数和薄膜厚度变化的灵敏度明显高于椭偏参数Psi。在椭偏数据处理中,椭偏参数Delta的测量精度直接影响薄膜光学常数和薄膜厚度的拟合精度。为了提高椭偏参数Delta的测量精度,可以选择入射角在膺布儒斯特角附近。所得结论对高精度椭偏测量具有指导意义。     

二维定心激光扫描器及其摆角测量系统的研制

简要介绍了一种二维定心偏转激光扫描器的工作原理和结构设计。对二维摆角的两种不同测量方式的优劣进行了比较,并详细介绍了采用光电位置传感器(PSD)实现摆角测量的系统,包括它的测量原理、光学系统构造和PSD后续信号处理电路。结果表明,所研制的二维定心激光扫描器摆角测量系统可以实现±7.5°的二维摆角和30°圆锥角的大范围扫描,其重复精度为0 05°,分辨率为0 01°。具有快速灵巧、实时性强、工作稳定、抗环境干扰能力强等优点。     

90°反射式相位延迟器的设计

铜蒸气激光反射镜在非正入射的时候 ,两个不同的偏振态之间会产生不同的相移。通过优化设计 ,在4 90～ 5 30nm之间p、s波获得了 90°的相移 ,同时也使反射率在 99 998%以上。Ag层的厚度对于相移不敏感 ,并且当其厚度大于一定值的时候 ,对反射率没有影响。根据误差分析 ,制备薄膜时其沉积速率精度控制在± 1%以下 ,在光谱范围内能达到± 15 2 8°的相移误差 ,相移均在 5 0 4nm处附近存在有一个收敛值。折射率的变化控制在± 1%以下 ,在光谱范围内能达到± 12 77°的相移误差。最外一层厚度变化± 1% ,其相移变化达到± 5 5°,2～ 5层和 9～ 16层对相移的影响也在 0 .5°之上 ,其余各层对相移影响非常的小。使用时的入射角控制在± 1°时 ,在光谱范围内能达到± 2 .86°的相移误差。在 5 30nm附近的波段对入射角不敏感。     

Phase-based method in heterodyne-modulated ellipsometer

A new common-path heterodyne-modulated ellipsometer with two-phase detection to measure the ellipsometric parameters of amplitude ratio (Ψ) and phase difference (Δ) between p- and s-polarizations of the thin film isotropic materials is proposed. Uniquely, the new scheme distinct from the other previous studies is only by taking two phases from heterodyne signals. Thus, the proposed system is a phase-sensitive modulated ellipsometer that can have the ability to measure the full range of the ellipsometric parameters with high sensitivity and eliminate the intensity fluctuation in system. The ability and performance of modulated ellipsometer on measurement of thin film thickness and ellipsometric parameters are verified by experiments. The errors regarding the ellipsometric parameter measurements are also discussed. The experimental results show that the average standard variation of measured ellipsometric parameters (Ψ and Δ) and the thickness measurement of silica thin film deposited on silicon substrate are 0.13°, 0.94°, and 0.55 nm, respectively. Accordingly, this new idea can be applied to measure isotropic thin film with extremely high absorbance that results in the poor signal/noise ratio in contrast extraction from heterodyne signals.     

Thickness dependent optical properties of titanium oxide thin films

TiO₂ thin films of different thickness were prepared by the Electron Beam Evaporation (EBE) method on crystal silicon. A variable angle spectroscopic ellipsometer (VASE) was used to determine the optical constants and thickness of the investigated films in the spectral range from 300 to 800 nm at incident angles of 60°, 70°, and 75°, respectively. The whole spectra have been fitted by Forouhi–Bloomer (FB) model, whose best-fit parameters reveal that both electron lifetime and band gap of TiO₂ thin film have positive correlation to the film thickness. The refractive indices of TiO₂ thin film increase monotonically with an increase in film thickness in the investigated spectral range. The refractive index spectra of TiO₂ thin films have maxima at around 320 nm and the maxima exhibit a marginally blue-shift from 327.9 to 310.0 nm with an increase in film thickness. The evolution of structural disorder in the TiO₂ thin film growth can be used to explain these phenomena.     

A high precision,polychromatic, automatic ellipsometer

The design and performance of a versatile, high precision, automatic ellipsometer, which follows rapid changes in surface properties, scans through the entire visible spectrum and through angles of incidence between 50° and 89°, is described. The state of polarization of the light beam is phase and amplitude modulated by means of two Faraday modulators working at a single frequency but in quadrature. Out-of-balance error signals are electronically processed and applied to a servodrive system which rotates the polarizing elements to the null positions. The angular positions of the prisms are measured by means of moiré fringe-counting systems which have digital displays reading to 0.001° over a range of 360°. The absolute accuracy of measurement of Δ and ψ, once all effects of intrinsic component imperfections and misalignments have been minimised, is better than ±0.013° in ψ and ±0.014° in Δ. The ellipsometer has been shown to work satisfactorily for a wide range of surface problems and in particular for surfaces with reflectivities as low as 0.001. The mechanical construction of the ellipsometer allows simultaneous movement of the two optical arms in opposite directions hence allowing a change in angle of incidence to be effected without any sample realignment. The ellipsometer has been designed with a sufficiently large sample space to allow the inclusion of bulky environmental chambers such as cryostats or vacuum systems and may be used to examine either vertical or horizontal surfaces.     

不同后处理方法对溶胶-凝胶SiO2膜层抗污染能力的影响

 以正硅酸乙酯作为前驱体,利用碱催化方式制备了SiO₂溶胶,采用提拉法在K9基片上镀制SiO₂单层薄膜,分别用热处理、紫外辐射处理、氨水加六甲基二硅胺烷气氛处理和酸碱复合膜4种后处理法对膜层进行处理,采用分光光度计、红外光谱、扫描探针显微镜、静滴接触角测量仪、椭偏仪等分析了薄膜的特性,通过真空环境加速污染实验对处理前后的膜层进行抗污染能力对比,结果表明：在碱性SiO₂膜层上加镀一层酸性SiO₂膜的复合膜层整体透过率仍保持在99%以上,疏水角达到128°,膜层真空抗污染能力大大加强。     

基于激光外差干涉术的薄膜厚度测量方法

针对光学薄膜厚度测量困难问题，提出了一种基于激光外差干涉术的薄膜厚度测量方法。采用经典迈克尔逊干涉光路，利用外差干涉原理将薄膜厚度差转换为光程差，以精密位移平台为扫描机构实现薄膜厚度的逐行扫描测量。测量系统在恒温实验条件下20 min内的漂移不超过8 nm，测量结果平均差小于1 nm，通过与椭圆偏振仪的测量结果比较，测量差值为12.97 nm，表明了该方法的可行性。     

Glass transition of poly(ethylene terephthalate)

It has been found that commercial poly(ethylene terephthalate) film exhibits current glow curves which have maxima at 73.5 ± 3.4°C and at 105.3 ± 3.4°C. These current glow curves were obtained by measuring the current flowing under zero bias as the temperature was raised 1°C/min. A typical curve, for untreated 1-mil du Pont Mylar A, is seen in Fig. 1. Although a paper on this study will shortly be submitted for publication, some conclusions of that paper may be stated here.     

Oxidation of titanium between 25°C and 400°C

The oxidation of Ti between 25°C and 400°C has been studied in an ultra high vacuum system with ellipsometry, Auger spectroscopy and surface potential difference. The surface potential difference is primarily sensitive to the adsorbed layer of oxygen, the Auger spectrometer is sensitive to the oxygen and Ti concentration at the oxide-gas interface and the ellipsometer is sensitive to the film thickness. Consequently, it was possible to follow the various processes separately during oxidation and oxide dissolution. Oxygen adsorbs in a percusor state as a molecule which dissociates and adsorbs in the atomic state. Reaction of atomic oxygen with Ti at the oxide-gas interface causes the stoichiometry to vary with the temperature, oxygen pressure and film thickness. At low temperatures and oxygen pressure the initial film growth follows a logarithmic time law. The predominant transport species is cationic. After initial oxidation, at higher temperatures and oxygen pressure, the predominant transport species is anionic. At constant temperature and oxygen pressure the oxide grows until the rate of growth is equal to the rate of dissolution into the metal. At this point the film thickness remains constant with time. Doping the Ti surface with Au results in a decrease in the oxide dissolution process due to blocking of interstitial diffusion paths by Au atoms.     

Polarization modulation imaging ellipsometry for thin film thickness measurement

A polarization modulation (PM) imaging ellipsometer is proposed and setup in order to measure precisely the thickness of thin film. Five images are collected sequentially by CCD camera with respect to five pre-determined azimuth angles of a quarter wave plate (QWP) during measurement. Then two-dimensional (2-D) distributions of the ellipsometric parameters ψ and Δ over the full dynamic range are obtained. Conceptually, PM imaging ellipsometer integrates the features of phase shift interferometry with conventional photometric ellipsometry by rotating the QWP sequentially to produce polarization modulation that is able to measure the thickness of a thin film in two dimensions precisely and quickly. The basic principle of PM imaging ellipsometer is derived wherein features such as common path configuration, full dynamic range of measurement, and insensitive to non-uniform response of the CCD are analyzed. The experimental results verify the ability and performance of PM imaging ellipsometer on 2-D thin film thickness, while the errors regarding the ellipsometric parameters measurements are discussed.     

In situ study of the Si-H bond in a-Si:H ultrathin films

A preliminary in situ analysis of the growth mechanisms and vibrational properties of plasma deposited amorphous silicon (a-Si:H) ultrathin films (d_f<200 Å) is presented. The hydrogen incorporation, as a function of the film thickness and the influence of the nature of the substrate on the early stage of the growth are studied by a new infrared phase modulated ellipsometer (IRPME). The Si-H bond (near 1990 cm^-1) is evidenced for the first time on films as thin as 5 Å. This new ellipsometer offers extremely high resolution thanks to a very small noise (0.02° in ψ and Δ).     

Effects of oxygen content on the microstructures and optical properties of thermochromic vanadium oxide thin films

Reactive direct current magnetron sputtering and in situ thermal oxidation were used to prepare vanadium oxide (VO _X ) thin films with different oxygen contents. X-ray diffraction, Fourier transform infrared spectroscopy and a field emission scanning electron microscope were employed to characterize the films. The optical properties of the VO _X films at room temperature and 90 °C were investigated by applying an spectroscopic ellipsometer with a three-layer model of BEMA/Brendel–Bormann oscillator/substrate. It was demonstrated that the vanadium–oxygen bonds were strengthened, the film thickness and roughness decreased, while the grain size increased with increasing oxygen content. The increase in oxygen content had the effect of decreasing the near-infrared reflectance and free-electron concentration of the film at 90°C due to the decrease in the amount of VO₂.