Determination of the optical constants and thickness of a thin slightly absorbing film by ellipsometric measurement

On the basis of an analysis of the properties of space constructed in coordinates of the ellipsometric angles and and the thicknessd ₁ of a thin slightly absorbing film, a graphical method of determining its index of refraction, index of absorption and thickness is proposed and discussed. From the two ellipsometric measurements, either for two different angles of incidence or for two different surrounding media, it is in principle possible to determine the chosen parameters characterizing the thin slightly absorbing film. The graphical method, however, seems to be less accurate and very laborious. The calculation is therefore proposed for an automatic computer. The ellipsometric measurements were carried out on a SAAB computer, according to a program elaborated in Algol. The results obtained and the values computed for the optical constants and the thickness of the thin slightly absorbing film are in good agreement with those found independently.     

A method for determining the optical constants of an absorbing film entering into the composition of a layered system

A matrix method of calculating the refractive index and the absorption factor of an absorbing film entering into the composition of a multilayer thin-film system (for example, of the dielectric-metal-dielectric type) from the measured transmission and reflection spectra of the system is proposed. The method is based on solution of the matrix equation for the layered system by the iterative method of continuous differential descent. The method developed was applied to determine the optical constants of a real silver film in the composition of a three-layer energetically efficient titanium dioxide-silver-titanium dioxide coating.     

Ellipsometric analyses for an absorbing surface film on an absorbing substrate with or without an intermediate surface layer

Various ellipsometric analyses have been derived to characterize the optical properties of a single-layer or a double-layer surface film overlaid on a substrate material. The general numerical technique is independent of the method (or methods) used in the series of ellipsometric measurements which provide the raw data. The convergence to unambiguously determined values of the unknown parameters is systematically carried out in the numerical search procedure. Selected examples are presented to illustrate the validity of various analyses and the possible usage of these analyses to optimize the experimental conditions and measurement methods.     

Generalized ellipsometry for biaxial absorbing materials: determination of crystal orientation and optical constants of Sb(2)S(3)

We demonstrate generalized ellipsometry for precise measurement of the principal indices of refraction, the extinction coefficients, and the orientations of the crystal a, b, and c axes of orthorhombic absorbing materials. Stibnite (Sb(2)S(3)) single crystals cut approximately parallel to (100), (010), (001), and (313) are studied at a representative wavelength of 589 nm. The (313) surface is sufficient for retrieval of all optical constants. The expected effects of surface over-layer formation are removed numerically. We propose generalized ellipsometry as a powerful tool for measurement of anisotropic optical function spectra of biaxial materials.     

Convenient and inexpensive determination of optical constants and film thickness of blended organic thin film

This work presents the study of optical constants and film thickness of blended organic thin films, emphasizing on the modeling procedure with modified genetic algorithm aided by absorption or transmittance spectra of both pure materials and the blends. Taking the blending of copper phthalocyanine(Cu Pc) and fullerene(C60) as an example, a simple, convenient and low-cost method for the determination of the optical constants and film thickness of blended organic thin films was demonstrated. New scheme for optical modeling of blended organic thin film was proposed by introducing peak energies of Cody-Lorentz oscillators of the pure materials, which were determined by fitting the film absorption of pure materials. These oscillators of pure materials could be recognized in the transmittance spectrum of their blends, and were further used as the initial searching ranges in the simulation of blended films. As a result, the constraint bounds of the unknown parameters were significantly reduced and modeling efficiency as well as fitting accuracy was improved. For instance, the fitting of the transmittance curves of blended films with different blending ratios reached reliable results in comparison with extinction coefficients obtained from experiment.     

A new spectroscopic method to get the optical constants of an absorbing material: The case of SrTiO3

To illustrate a previous paper (1) we compute the complex refractive index = n -jk of a SrTiO₃ single crystal plate cut persendicular to the axis, at =270 cm^–1 with a new spectroscopic method where the SrTiO₃ plate is covered with a thin Ge film. Irregular spaced interferences fringes lead to a direct determination of n and k at the minima and maxima. In the case of SrTiO₃ the results are in good agreement with Kramers-Kronid determinations made by Barker and Tinkham (2).     

IR spectra of the optical constants of an industrial high-pressure polyethylene film

The IR spectra of the real n(ν) and imaginary κ(ν) parts of the complex refractive index of an industrial high-pressure polyethylene film are measured by the methods of transmission and attenuated total reflectance spectroscopy in the range 700–750 cm^?1 taking into account the anisotropy and the structural inhomogeneity of the film over its thickness. It is proposed to use these spectra as the reference spectra for polyethylene films in the range around 720 cm^?1.     

The accuracies of photometric, polarimetric and ellipsometric methods for the optical constants of thin films

The inherent accuracies of various techniques for determining the optical constants of thin films have been assessed by computing the errors produced in n and k by known experimental errors in the optical functions being measured. The results are presented as arrays of error parallelograms in the n–k plane covering d/λ from 0.001 to 0.20 and θ from 5° to 85°.The largest regions of accuracy, in the form of annular quadrants, were obtained using the mixed photometric and polarimetric functions at small angles of incidence. Ellipsometry gives similar results at large angles of incidence but for photometry and for polarimetry the accurate regions were in the form of two lobes.The effects of errors in x and θ were also considered.     

弱吸收基底上弱吸收薄膜的光学常数计算方法

采用一种相对简单而又精确的光度法来计算弱吸收基底上弱吸收薄膜的光学常数,为低损耗紫外薄膜的设计与实现提供了理论基础。采用JGS1型熔融石英基底,制备了MgF2与LaF3材料的单层膜,获得了JGS1型熔融石英基底及MgF2与LaF3薄膜的光学常数色散曲线。结果显示:在200 nm左右处,JGS1型熔融石英基底的吸收已经比较明显,消光系数在10-8量级,因此,应考虑基底的弱吸收,以提高薄膜光学常数的计算精度。     

The influence of the substrate on the optical constants of Al films

Attenuated total reflection (ATR) spectroscopy employing a prism and a dielectric spacer layer is used to determine the optical constants of vacuum deposited aluminium films. In the energy range of the 1.5 eV interband transition, a strong dependence of the optical constants on the material of the underlying layer is found. This dependence is attributed to structural effects in the Al film.     

A contribution to the determination of optical constants

A method is described for determining optical constants by means of a computer on the basis of intensity measurements and the computed results for a weakly absorbing substance in the form of a thin film are used to demonstrate the multiplevaluedness of the transmission-reflection measuring method.     

Proton radiation effects on optical constants of Al film reflector

The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charged particles in the Earth radiation belt, the reflectors could be deteriorated. In order to reveal the deterioration mechanism, the change in optical constants of Al film reflector induced by proton radiation with 60\,keV was studied in an environment of vacuum with heat sink. Experimental results showed that when the radiation damage primarily occurs in the Al reflecting film, the extinction coefficient k will gradually decrease with increasing radiation fluence, which results in the decrease of the energies of reflective light. Therefore, the proton radiation induced an obvious degradation of spectral reflectance in the wavelength region from 200 to 800\,nm on the Al film reflector.     

基片光学特性对薄膜光强透过谱的影响

在考虑基片与空气界面反射率以及基片吸收不能忽略的情况下，对常见的基片上薄膜的光强透过率公式进行了修正，导出了该情况下的透过率公式．以非晶硅薄膜为研究对象，采用模拟计算说明基片光学特性对薄膜光强透过谱的影响．     

A method for determining optical constants, dimensions, and concentrations of “soft” absorbing particles in the brightening band region

We investigate the possibilities of creating a method for estimating the optical constants, dimensions, and concentrations of “soft” absorbing particles by applying a theoretical analysis of the angular dependence of the intergrated indicatrix, overall characteristics of light scattering, and absorption on the phase shift and diffraction parameter of particles in the brightening band region. We show that using the investigated optical characteristics, it is possible to determine the unknown parameters of a suspension from experimental data. Institute of Biophysics, Siberian Branch of the Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 807–812, November–December, 1997.     

Colored LiF: an optical material for all seasons

Colored LiF salt has been always considered a singular optical material among alkali halides and other dielectric crystals for its peculiar characteristics, which in due time have been applied with success in thermoluminescence and laser technology. Lately, while the two previous topics have been revived, new relevant results have been obtained in the optoelectronic field by using both bulk crystals and newly characterized thin films. In practice, miniaturized photoluminescent patterns can be produced rather easily by using low-energy electron beams and soft X-rays. So, LiF salt is becoming a new interesting photonic material with promising developments in basic reasearch and applications as well.     

A method of precise determination of the optical constants of uniaxial crystals from the compensator parameters

A method of determination of the refractive indices of uniaxial crystals from the compensator parameters is proposed. In this case, the accuracy is limited by the temperature fluctuations inside a crystal. The orientation of the optical axis with respect to the surface and the thickness and the thermal expansion coefficient of the crystal can be determined additionally. This method can be used for precise determination of the refractive indices and absorption coefficients of biaxial crystals. Experimental results of determination of the temperature coefficients of the refractive indices and of linear expansion for a plane-parallel plate cut from artificial crystalline quartz parallel to the optical axis are presented.     

Evaluation of the substrate effect on indentation behavior of film/substrate system

A method to evaluate the substrate effect quantitatively in film indentation is proposed. For the thin film deposited on the substrate, the power function relationship is used to describe the loading curve of the film indentation behavior. The loading curve exponent of the power function which is the fitting parameter can reflect the substrate effect quantitatively. The finite element method is used to simulate the nanoindentation process of the film/substrate system. The loading curve exponent can be obtained from the simulation results. A substrate effect factor based on the loading curve exponent is defined to characterize the effect of the substrate on film indentation. Meanwhile, the dimensionless function of the loading curve exponent related with the material properties and indentation depth is obtained. The results can be helpful to the measurement of the mechanical properties of thin films by means of nanoindentation.