Analysis of systematic errors in Mueller matrix ellipsometry as a function of the retardance of the dual rotating compensators

A dual rotating compensator ellipsometer based on the optical PC1SC2A configuration described by Collins [1, chap. 7.3] has been developed. The systematic errors for this configuration if the compensators are quarter-wave plates have been already studied [2, 3, 4]. Smith [5] has demonstrated that the optimum retardance of a dual-rotating-retarder (DRR) instrument must be equal to 127° compared to the quarter-wave (90°) retarders generally used. In this condition random errors are optimized. The aim of this work is to used such retarders and verify if the systematic errors due to uncertainties of the optical elements (i.e. analyzer, polarizer, first and second compensators) are improved too. For each optical element in different configurations like single or 4-zone average measurements, the systematic errors are given and compared according to the compensators. It is demonstrated that using a 127° instead of quarter-wave retarders coupled with 4-zone averaging measurement is the best configuration for this instrument. These results were confirmed by a statistical study.     

Determination of the refractive index of single crystal bulk samples and micro-structures

We present comparative studies for the exact determination of the refractive index of single crystals using spectroscopic ellipsometry and photonic-mode-structure investigations by means of spatially resolved photoluminescence spectroscopy, especially in the near band-gap spectral range. By applying such complementary methods we can overcome the uncertainties in the determination of the bulk refractive index introduced by surface properties. The physical effects used are the electromagnetic field reflection used by spectroscopic ellipsometry at large scale planar single crystals and the whispering-gallery-mode formation by total internal reflection in confined micro-structures. We demonstrate the applicability of such studies using the example of uniaxial ZnO bulk samples and micro-wires. By assuming a surface near region with electronic properties different from the bulk material, the method presented here gives the refractive index dispersion for both types of samples in an energy range from 1 to 3.4 eV.     

Rotating compensator sampling for spectroscopic imaging ellipsometry

In this work, a rotating compensator sampling for spectroscopic imaging ellipsometry (SIE) is presented and demonstrated by characterization of a SiO₂ nanofilm pattern on Si substrate. Experiment results within spectrum of 400-700 nm show that the rotating compensator sampling is valid for SIE to obtain the ellipsometric angle distributions ψ (x, y, λ) and Δ (x, y, λ) over the thin film pattern, the sampling times of ψ (x, y) and Δ (x, y) with 576 × 768 pixels under each wavelength is less than 8 s, the precision of fitting thickness of SiO₂ is about 0.2 nm and the lateral resolution is 60.9 μm × 24.6 μm in the parallel and perpendicular direction with respect to the incident plane.     

Optical Storage

Abstract

Digital and holographic optical storage systems are compared. Requirements for the improvement of current storage systems are defined. Techniques to study storage properties of polymer liquid crystals (PLCs) are described; they include diffraction grating, polarization holography, spectroscopic methods, refractive index determination (interferometry, birefringence), methods of surface characterization, and testing reversibility and the number of write-read cycles. Results are reported for several PLCs and interpreted in terms of the effects of the choice of the main chain, the spacer, the chromophore, the LC components, the molecular weight, photoorientation and the surface morphology.     

Optical and chemical characterization of thin TiNx films deposited by DC-magnetron sputtering

Thin titanium nitride (TiN_x) films were deposited on silicon substrates by means of a reactive DC-magnetron plasma. Layers were synthesized under various conditions of discharge power and nitrogen flows in two operation modes of the magnetron (the so-called “balanced” and “unbalanced” modes). The optical constants of the TiN_x films were investigated by spectroscopic ellipsometry (SE). X-ray photoelectron spectroscopy (XPS) was used to determine the relative atomic concentration and chemical states of the TiN_x films. The density and thickness of the films have been investigated by means of grazing incidence X-ray reflectometry (GIXR). The results of the layer analyses were combined with plasma investigations carried out by means of energy resolved mass spectrometry (ERMS) under the same conditions. It is shown that the magnetron mode has a clear influence on the titanium deposition rate and the incorporation of nitrogen into the layers.     

Spectroscopic ellipsometry analysis of GaAs1 − xNx layers grown by molecular beam epitaxy

In this work, we present the effect of nitrogen incorporation on the dielectric function of GaAsN samples, grown by molecular beam epitaxy (MBE) followed by a rapid thermal annealing (for 90 s at 680 °C). The GaAs_1 − xN_x samples with N content up to 1.5% (x = 0.0%, 0.1%, 0.5%, 1.5%), are investigated using room temperature spectroscopic ellipsometry (SE). The optical transitions in the spectral region around 3 eV are analyzed by fitting analytical critical point line shapes to the second derivative of the dielectric function. It was found that the features associated with E₁ and E₁ + Δ₁ transitions are blue-shifted and become less sharp with increasing nitrogen incorporation, in contrast to the case of E₀ transition energy in GaAs_1 − xN_x. An increase of the split-off Δ₁ energy with nitrogen content was also obtained, in agreement to results found with MOVPE GaAs_1 − xN_x grown samples.     

Formation of Pentacene wetting layer on the SiO2 surface and charge trap in the wetting layer

We studied the early-stage growth of vacuum-evaporated pentacene film on a native SiO₂ surface using atomic force microscopy and in-situ spectroscopic ellipsometry. Pentacene deposition prompted an immediate change in the ellipsometry spectra, but atomic force microscopy images of the early stage films did not show a pentacene-related morphology other than the decrease in the surface roughness. This suggested that a thin pentacene wetting layer was formed by pentacene molecules lying on the surface before the crystalline islands nucleated. Growth simulation based on the in situ spectroscopic ellipsometry spectra supported this conclusion. Scanning capacitance microscopy measurement indicated the existence of trapped charges in the SiO₂ and pentacene wetting layer.     

月球及火星探测任务中光谱技术研究与应用

光谱仪器获取目标光谱信息或光谱图像,具备物质成分无损识别和定量反演能力,已成为国内外月球和火星探测任务重点配置的科学载荷,为表面物质成分及矿产资源、形成与演化历史及资源利用等研究提供重要依据.本文简要介绍了近年来国内外月球及火星探测任务中光谱技术的研究进展与应用现状,概述了中国探月工程及天问一号探测任务中七台光谱仪器及...     

IPS液晶取向膜表面光学各向异性DΔ的研究

针对共面转换IPS(In-Plane-Switching)液晶显示模式取向膜,利用反射椭偏消光法测量了取向膜表面的光学各向异性DΔ值。研究了在不同摩擦条件和亚胺化温度条件下,取向膜表面光学各向异性值DΔ值的变化。研究结果表明,随着亚胺化温度升高,DΔ值呈现下降趋势。在摩擦强度各因子中,压入量和转速对于DΔ值影响较大。DΔ值可作为一种定量化评价取向膜取向状态的方法,并可作为生产过程中对于液晶稳定性取向的管控方法使用。     

利用15N(d,p)16N反应研究16F低能级质子宽度

¹⁶F是质子滴线附近的奇特原子核,它的所有态均不稳定,会发生质子衰变。目前¹⁶F前4个态的自旋宇称及激发能已通过实验精确测定,但能级宽度仍存在较大分歧。本工作通过¹⁵N(d,p)¹⁶N反应角分布的高精度测量,确定了¹⁶N基态和前3个激发态的谱因子;进而根据镜像核的电荷对称性,用¹⁶N的中子谱因子导出了¹⁶F基态和前3个激发态的质子宽度分别为（29.9±4.1） keV、（108±13） keV、（5.04±0.48） keV和（14.5±1.4） keV。本工作通过一个独立的实验方法为¹⁶F的质子宽度提供了一个重要的交叉检验。