SmS光学薄膜研究新进展

SmS光学薄膜是一种可用于全息记录的薄膜材料,由于其特殊的结构特点,在全息记录、光学开关、压敏元件等领域具有广阔的应用前景.通过对SmS薄膜的结构特点、制备方法、相变原理和应用领域等方面的综述,提出并设计了水热法、仿生法、溶胶-凝胶法及电沉积法等制备SmS薄膜的几种湿化学方法,展望了SmS薄膜今后的研究和发展趋势.     

不透明薄膜厚度的光干涉法测量以及台阶的影响

提出使用数字CCD拍摄光干涉条纹,使用图像处理软件进行灰度值扫描分析光干涉条纹的方法,对不透明薄膜进行光干涉法测厚.数字CCD和图像处理软件的结合使用能够最大限度的降低目测带来的误差,并且也避免了使用复杂的干涉条纹提取算法,可以方便、准确地对不透明薄膜进行光干涉法测厚.同时我们使用光干涉法和轮廓仪法对不同高度遮挡物形成的台阶进行了对比测量,分析了不同台阶边缘斜坡对于光干涉法测量结果的影响,指出在制备台阶时遮挡物的高度必须满足一定的条件,并且根据这个条件推导出在我们的磁控溅射设备中,遮挡物高度小于50 μm可以得到满足光干涉法测厚条件的台阶.     

硅在红外光学薄膜中的应用研究

介绍了硅的理化特性以及在光学薄膜设计中的应用特点.对电子束沉积硅薄膜时的温度、真空度进行了确定,并对其沉积速率的稳定性以及石墨坩埚的使用方法进行了研究.利用分光光度法测定了硅膜在0.5μm～5 μm波段范围内的折射率分布曲线.     

实时测量器件中光学薄膜厚度的新方法研究

从薄膜光学理论出发，阐述了利用光学反射比实时测量特种器件中光学薄膜厚度的原理，介绍了测试仪器，分析了测试结果。在已知基底的折射率、光学薄膜的折射率、消光系数及入射光波长的情况下，可计算出光学薄膜的反射比随厚度变化的理论曲线，实验曲线与理论曲线相比较，可实时获得薄膜的厚度信息，这对控制薄膜工艺很有益处。     

多层薄膜光学常数的椭偏法研究

研究了椭偏测量中多层薄膜拟和模型建立的过程,并对一未知多层光学薄膜进行了椭偏分析,建立了substrate/film1/EMA/film2/srough的物理结构模型.采用椭偏法,在首先确定出基底光学常数的基础上,提出了从单层、双层、三层逐次建模拟和的分析方法.研究结果表明:对于透明或弱吸收光学薄膜,采用柯西公式可以较好表征材料的色散关系.椭偏分析最终得到的未知薄膜基本结构为G(1.52)/2.0312(203.0 nm)1.4636(170.1 nm)2.079 1(170.4 nm)/A,膜系设计及分光光度计测量的透射光谱证实了这一结果.对多层膜厚度和光学常数的分析表明,椭偏法仍然是一种行之有效的薄膜光学常数测量方法.     

光学多层膜减小电场强度的一种新设计方法

制作 损伤阈值光学薄膜不仅需要沉积工艺有所突破,而且需要膜系设计也有所改进,用于减少强激光对薄膜的损伤因素。本文提出了一种计算机算法用于改善光学多层膜内驻波场分布,肖弱电场强度对薄膜的损伤。其物理概念清清晰,理论推导,算法编程实用简单。     

锗(Ge)光学薄膜在不同沉积温度下的聚集密度研究

锗(Ge)薄膜是中长波红外区最常用的光学薄膜之一,高的聚集密度对于提升光谱稳定性和光学薄膜元件的品质非常重要.选用纯度为99.99％的Ge材料,在5× 10-4 Pa左右的真空压力下用电子束蒸发沉积,石英晶振仪将沉积速率控制在0.8～1.0 nm/s范围,宝石片基片上的膜层厚度约为0.8～1.0μm,在不同沉积温度下制...     

膜层的光学薄膜参数测量方法研究

简述了研究膜层光学薄膜参数测量方法的必要性。详细介绍了各种测量方法的理论思想、测量准确度、测量范围。综合比较了各种测量方法的优缺点和适用性,研究了测量不同类型薄膜系统膜层光学薄膜参数的最佳测量方法。最后总结了膜层光学薄膜参数测量方法的发展,并提出了建议。     

激光器全反射介质膜的制作原理与光学厚度测定

阐述了光学薄膜的镀制原理、反射率推算,阐述了镀制全反射介质薄膜过程中光学厚度的测定方法-极值法测量的原理和所用光线的波长,阐述了得到高反射率的条件,给出了测量膜厚的实验系统装置,并叙述了镀制17层全反射介质薄膜的过程和测量的方法,最后给出了17层全反射介质薄膜的反射率测量结果。     

阴极恒电流法制备SmS光学薄膜

以SmCl3·6H2O和Na2S2O3·5H2O为原料,采用电沉积法在单晶硅(100)和玻璃基板制备了SmS光学薄膜.采用XRD、AFM和紫外可见光分光光度计对薄膜进行了表征.研究了[Sm3 ]/[S2O32-]、溶液的pH值对于薄膜的物相的影响.结果表明:在[Sm3 ]/[S2O32-]=1:2,控制溶液pH值为4.50以及沉积1h的条件下,可制备出70nm厚单一晶相且表面比较平整的SmS薄膜,薄膜具有(331)方向的取向性.紫外光谱测试表明所制备的SmS薄膜具有290～300nm的紫外吸收特性,薄膜的禁带宽度约为3.6eV.     

Modified channeled spectrum for fast measurement of thin films

A simple and effective technique for the simultaneous measurement of the refractive index and the thickness of thin films is proposed. The method is based on the spectral dependence of the visibility of interference fringes that result from thin-film interference when the film is illuminated with a white light. The film is on the special substrate, and an optical contact is provided between them. The measurement consists of finding the local change of the fringes' visibility in the observed channeled spectrum expressed as the seaming change of the fringes' periodicity. The method can be applied for real time optical inspection during the manufacturing of thin polymer films.     

Effects of buffer layer thickness on properties of ZnO thin films grown on porous silicon by plasma-assisted molecular beam epitaxy

ZnO thin films with different buffer layer thicknesses were grown on Si and porous silicon (PS) by plasma-assisted molecular beam epitaxy (PA-MBE). The effects of PS and buffer layer thickness on the structural and optical properties of ZnO thin films were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The ZnO buffer layers, the intensity of the (002) diffraction peak for the ZnO thin films and its full width at half maximum (FWHM) decreased with an increase in the thickness of the ZnO buffer layers, indicating an improvement in the crystal quality of the films. On introducing PS as a substrate, the grain sizes of the ZnO thin films became larger and their residual stress could be relaxed compared with the ZnO thin films grown on Si. The intensity ratio of the ultraviolet (UV) to visible emission peak in the PL spectra of the ZnO thin films increased with an increase in buffer layer thickness. Stronger and narrower UV emission peaks were observed for ZnO thin films grown on PS. Their structural and optical properties were enhanced by increasing the buffer layer thickness. In addition, introduction of PS as a substrate enhanced the structural and optical properties of the ZnO thin films and also suppressed Fabry-Perot interference.     

Characterization of thin TiO2 films prepared by plasma enhanced chemical vapour deposition for optical and photocatalytic applications

Thin titanium oxide films were deposited using a radio frequency (RF) plasma enhanced chemical vapour deposition method. Their optical properties and thickness were determined by means of ultraviolet-visible absorption spectrophotometry. Films of the optical parameters very close to those of titanium dioxide have been obtained at the high RF power input. Their optical quality is high enough to allow for their use in a construction of stack interference optical filters. At the same time, these materials exhibit strong photocatalytic effects. The results of structural analysis, carried out by Raman Shift Spectroscopy, show that the coatings posses amorphous structure. However, Raman spectra of the same films subjected to thermal annealing at 450 °C disclose an appearance of a crystalline form, namely that of anatase. Surface morphology of the films has also been characterized by Atomic Force Microscopy revealing granular, broccoli-like topography of the films.     

ITO透明导电薄膜厚度与光电性能的关系

透明导电薄膜的厚度制约其光电性质。本研究利用磁控溅射技术制备了厚度变化范围为200-1500nm的ITO薄膜,探索了薄膜颜色、可见光透过率、面电阻与膜厚的关系。薄膜颜色随着膜厚的增加呈现有规律的变化,可见光透过率随薄膜厚度的增加而呈现振荡下降趋势,并出现了极大值(紫红色),振荡趋势可用多光束干涉解释;薄膜面电阻随膜厚的增加呈减小趋势,薄膜厚度为1387nm时,面电阻为1.3Ω/□,薄膜最小电阻率为1.8×10-4Ω.cm。文章给出了可以通过选择恰当的薄膜厚度,以尽可能满足透明导电薄膜面电阻、透过率两个相互矛盾的指标。     

WO3电致变色薄膜制备过程中光学膜厚测量监控技术的研究

采用真空电子束蒸发方法制备WO3电致变色薄膜过程中，利用极值法光学膜厚测量技术监控薄膜的光学特性，对不同光学膜厚的WO3薄膜的原始态、着色态和退色态的光谱特性进行了对比分析。测试采用二电极恒电压方法，用分光光度计实时测量透过率的变化。结果证明以ITO玻璃作为比较片，极值法监控薄膜光学膜厚，当反射率达到第一极小值，即透过率达到第一极大值时，WO3薄膜得到最好的综合电致变色特性。     

Refractive index and thickness determination of transparent films: An interference method

A method is developed for determining the refractive index of transparent films of medium thickness over a spectral region in which the dispersion cannot be neglected. The advantage of the method is that it does not require any information about the thickness or the interference order. The method is tested numerically and applied to a CdS film in the region below the fundamental absorption.     

Optical characterization of dielectric and semiconductor thin films by use of transmission data

A method to calculate the optical functions n(lambda) and k(lambda) by use of the transmission spectrum of a dielectric or semiconducting thin film measured at normal incidence is described. The spectrum should include the low-absorption region and the absorption edge to yield the relevant optical characteristics of the material. The formulas are derived from electromagnetic theory with no simplifying assumptions. Transparent films are considered as a particular case for which a simple method of calculation is proposed. In the general case of absorbing films the method takes advantage of some properties of the transmittance T(lambda) to permit the parameters in the two regions mentioned above to be calculated separately. The interference fringes and the optical path at the extrema of T(lambda) are exploited for determining with precision the refractive index and the film thickness. The absorption coefficient is computed at the absorption edge by an efficient iterative method. At the transition zone between the interference region and the absorption edge artifacts in the absorption curve are avoided. A small amount of absorption of the substrate is allowed for in the theory by means of a factor determined from an independent measurement, thus improving the quality of the results. Application of the method to a transmission spectrum of an a:Si(x)N(1-x):H film is illustrated in detail. Refractive index, dispersion parameters, film thickness, absorption coefficient, and optical gap are given with the help of tables and graphs.     

Refractive index, extinction coefficient and DC conductivity of amorphous arsenic triselenide thin film doped with silver

Thin films of arsenic triselenide doped with silver were prepared by thermal evaporation of the bulk-quenched materials. Structural investigations have been carried out by using X-ray diffraction and X-ray fluorescence. The differential scanning calorimetry is used to measure the glass transition temperature of the samples under investigation. The Swanepoel method based on the use of the maxima and minima in the interference fringes has been successfully utilized for accurate determination of the film thickness and optical parameters. The technique used took into consideration the non-uniform nature in the film thickness. Using the exact calculation of the film thickness the real refractive index, the extinction coefficient, the optical bandgap energy and the oscillator and dispersion energies were obtained as a function of the silver contents. The DC conductivity was found to depend on the silver content.     

Optical characterization of sputtered semitransparent zirconium nitride films

Thin semi-transparent ZrN films have been prepared using reactive dc magnetron sputtering. The films had thickness from 11 to 43 nm and were grown on heated and room temperature glass substrates. The optical constants, N=n+ik, of the thin films have been determined with an RT inversion method in the wavelength interval 0.40 to 2.0 μm. The thickness of the films was determined from the photometric measurements. The optical properties of the thin films on glass were compared to opaque and thin ZrN films grown on single crystalline Si. The Drude parameters were calculated from the measured optical constants in the relaxation region of the thin films. The relaxation time, τ, of the thin films was found to increase with film thickness, substrate temperature and substrate crystallinity. The relaxation time is the mean free time for the electrons between collisions and a long relaxation time corresponds to a film with high optical quality. The observed decrease of τ with decreasing film thickness can be explained by the higher statistical probability of the electrons in a thin film to collide with the two surfaces of the film. Another explanation to the decrease of τ with film thickness is scattering from grain boundaries and lattice impurities. The higher optical quality of films grown on heated substrates is probably due to an increased grain size. The measured optical constants were compared with calculated optical constants, using the Drude model, and the optical behaviour of thin ZrN films was found to be well described by the screened free-electron model.