The dependence of ellipsometric parameters Δ and Ψ on refractive index of superficial film (original) (raw)
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American Journal of Optics and Photonics, 2015
The ellipsometrical analysis of the external specular reflection of light on nonabsorbing superficial films allows us to know factors which influence the ellipsometric measurement of the analyzed system. For optical nonabsorbing superficial films the curves ∆=f(d f ) and Ψ=f(d f ) are periodical, while the curves ∆=f(Ψ) are closed. The paper presents observations on the dependence of the ellipsometric parameters ∆ and Ψ on d f . The analysis of the periodicity of these curves allows us to correctly determine the film thickness for thicknesses greater than d min . The value of d min depends on the refractive index n f of the surface film, the incidence angle φ 0 and the wavelength λ of the incident radiation. The dependence of d min on n f , φ 0 and λ is analyzed. From the curve shape we can draw conclusions with respect to the domain of small errors, allowing us to correctly determine the thickness and refraction index of superficial films.
Journal of physics, 2020
Ellipsometry is an optical method that allows very accurate determination of the optical constants of surfaces or determination of the thickness and optical constants of superficial films on solid substrates. If the determination of the optical characteristics of transparent superficial films is relatively simple, at least two ellipsometric measurements are required for optically absorbent films: at two different angles of incidence or using two different incidence media. This involves additional problems with errors related to the realignment of the ellipsometer. Ways to obtain the thicknesses and optical constants for thin or thick transparent or non-transparent superficial films are presented. A simple graphical method is presented to determine the thicknesses and optical constants of thin absorbent films with non-uniform thickness.
Thin Solid Films, 2013
Standard variable-angle spectroscopic ellipsometry, mapping spectroscopic ellipsometry with microspot and imaging spectroscopic reflectometry are applied to optical characterisation of a thin SiO x C y H z film considerably non-uniform in thickness and which is also suspected of non-uniformity also in the optical constants. It is shown that using the combination of these three optical methods, enables us to determine the spectral dependencies of the optical constants of the film together with parameters characterising the shape of thickness non-uniformity and fine map of local thickness. The mapping spectroscopic ellipsometry with microspot enables deciding whether the film is non-uniform in optical constants. For the thin film studied it is found that the non-uniformity in optical constants is under experimental accuracy. The consistency of results obtained using individual techniques is checked and the advantages and disadvantages of the techniques are discussed.
Monolayer film analysis by total internal reflection ellipsometry
Lithuanian Journal of Physics, 2007
The surface plasmon resonance (SPR) method combined with spectral ellipsometry was used to study the chemically formed octadecanthiol (ODT) monolayer on a gold film in Kretchmann configuration. Measurements were made with a commercial spectral ellipsometer GES-5 (SOPRA). The optical constants of an Au film and ODT at 1000 nm wavelength were determined by the best fit procedure from experimental data (Au: n = 0.202, k = 5.970 and ODT: n = 1.4, k = 0). Combination of the SPR method with advantages of phase measurements of ellipsometry demonstrated a substantial increase in sensitivity (more than one order of magnitude) compared with conventional ellipsometry.
Numerical Algorithm for Spectroscopic Ellipsometry of Thick Transparent Films
Applied Optics, 1998
We present a numerical method for spectroscopic ellipsometry of thick transparent films. When an analytical expression for the dispersion of the refractive index ͑which contains several unknown coeffi-cients͒ is assumed, the procedure is based on fitting the coefficients at a fixed thickness. Then the thickness is varied within a range ͑according to its approximate value͒. The final result given by our method is as follows: The sample thickness is considered to be the one that gives the best fitting. The refractive index is defined by the coefficients obtained for this thickness.
Multiple sample analysis of spectroscopic ellipsometry data of semi-transparent films
Thin solid films, 1998
When analyzing spectroscopic ellipsometry data it can be difficult to find unique solutions if, for instance, the dielectric function of a film must be found together with the film thickness. One method to find the solutions is 'multiple sample analysis'. The basic assumption for this method is that the optical properties of the unknown layers are identical in all samples. In the analysis procedure a set of samples with different film thicknesses are prepared and measured, preferably at multiple Ž . angles of incidence. Several one for each sample identical optical models are then defined with coupled optical properties of the unknown layers and all data are fitted simultaneously. This will give solutions for the dielectric function of the films and the film thicknesses due to parameter decoupling. The analysis can also be extended to more complex samples including more than one film thickness, surface and interface roughness, and porosity. In this study we have applied the multiple sample analysis method to find dielectric functions, film thicknesses and surface roughnesses of thin films of Ta 2 O, ScN and CeO 2 .
Transmission and Reflection Ellipsometry of Thin Films and Multilayer Systems
Applied Optics, 1998
Ellipsometric studies are generally carried out in the reflection mode rather than in the transmission mode, requiring invariably opaque substrates or substrates in which the backreflection is minimized or suppressed by different methods. In the present research we used a transmission and reflection photoellipsometry method to study electrochromic materials and their multilayer systems deposited on thick substrates. The role of the substrate is examined carefully, and the contributions from multiple reflections in the substrate are taken into account in the theoretical treatment. This procedure not only allows the study of thin films deposited on quasi-transparent substrates, but when carried out in conjunction with reflection measurements it greatly improves the accuracy in the determination of the optical constants. Optical measurements are carried out on an automatic reflection transmission spectroscopic ellipsometer. Solid-state ionic materials used in electrochromic systems such as indium tin oxide, tungsten oxide, and their multilayer structures deposited on glass substrates are used as examples. A software based on the above theory, OPTIKAN, was developed to model and analyze such systems. It is demonstrated that the photoellipsometry method proposed is especially suited to analyzing electrochromic materials and transmitting devices in a nondestructive way.
Vacuum, 2005
In this paper, results concerning the optical characterization of TiO 2 thin films prepared by magnetron sputtering onto K64 glass plane-parallel plates are presented. The spectral dependences of the refractive index and extinction coefficient of these TiO 2 thin films are introduced within the spectral region 230-1000 nm. For determining the values of these optical constants the method based on a combination of variable angle spectroscopic ellipsometry and spectroscopic photometry employing experimental data, of the transmittance and reflectances measured from both the sides of the films is used. For treatment of all the experimental data, the method utilizing Cauchy and Urbach formulae together with the single-wavelength method is employed. It is shown that the TiO 2 films studied are homogeneous in refractive index and uniform in thickness. Moreover, the values of roughness parameters of the upper boundaries of the TiO 2 films are determined. Furthermore, it is shown that the band gap value of the films corresponds to 400 nm, i.e. 3.1 eV.
Ellipsometric characterisation of thin films non-uniform in thickness
Thin Solid Films, 2011
Ellipsometric formulae for thin films non-uniform in thickness are presented. A general type of thickness nonuniformity is considered and the influence of the varying angle of incidence is taken into account. The presented formulae are applied to the optical characterisation of polymer SiO 2 -like thin films exhibiting a relatively strong thickness non-uniformity. It is shown that the complete optical characterisation of these polymer thin films can be performed. Thus, the spectral dependences of the optical constants, mean thickness and parameters related to the shape of thickness non-uniformity can be determined.
Thin Solid Films, 1997
Ellipsometry is known to be a powerful and convenient tool for investigations of the optical properties of thin films. However, in investigations of thin anisotropic films its usage is not as wide as it could be, due to a limitation in resolving the components of the dielectric tensor in the case of the transverse optical anisotropy of thin films. This problem may be solved by the immersion technique, but immersion in its standard variant of changing the ambient medium may add new uncertainties to the system under investigation. The changing of reflecting properties of a substrate is proposed in this work for the investigation of such anisotropy. To avoid the ambiguity connected to different chemical properties of different substrates, it is convenient to use the substrates from the same material, but with different thicknesses of an oxide film. Such systems have different optical properties, at the same time possessing identical chemical ones. It is shown here that the usage of such structure gives sensitivity to the transverse optical anisotropy. Calculations of the sensitivity and precision of the determination of film parameters by means of the proposed method, as well as the modeling determination of anisotropic optical parameters of a thin film, are presented. © 1997 Elsevier Science S.A.