Karel Navrátil

IV: Scattering of Light from Multilayer Systems With Rough Boundaries

Publisher Summary This chapter discusses the scattering of light from multilayer systems with rough boundaries. Multilayer systems are employed in various branches of applied optics and the optics industry. The chapter reviews the important theoretical and experimental results concerning the optics of rough multilayer systems. The physical models of rough boundaries (surfaces) play an important role in the optics of rough multilayer systems. The theoretical approaches enable us to calculate optical quantities corresponding to the rough boundaries and rough thin film systems. The interpretation of experimental data using the theoretical results introduced has been described. Relevant methods for the optical characterization of rough surfaces, rough single layers and rough multilayer systems have been outlined. The chapter also focuses on the scattering of X-rays from rough surfaces and thin film systems with rough boundaries.

Optical properties of thin films of poly(methyl–phenylsilylene)

We report the results of optical studies of thin films of poly(methyl-phenylsilylene) prepared on single-crystalline silicon and fused quartz substrates using the casting and spin coating technology. From near-normal incidence reflectance, we have determined the spectral dependence of the complex dielectric function and the complex refractive index in the energy interval from 1 to 7 eV. This optical database is listed in tabular form. Four absorption bands are clearly observable in the range below 7 eV. We have also performed a comparison with the transmission data from solutions.

INTERPRETATION OF INFRARED TRANSMITTANCE SPECTRA OF SIO2 THIN FILMS

We have investigated optical properties of thermally grown SiO2 layers within the thickness range 150 to 500 nm. The complex dielectric constant ε(ν˜) can be represented by six Lorentz-Gauss oscillators, which allow us to determine the optical constants of SiO2 films by fitting IR transmittance spectra. The spectra of ε(ν˜), unlike transmittance, are not affected by the multiple reflections at the film/air and film/substrate interfaces. Changes of optical constants for different thicknesses can be attributed to changes of physical properties of the film. We compare dielectric functions of samples oxidized at different conditions and discuss the influence of thickness and surface preparation of the substrate. We also compare our results with the dielectric function of bulk vitreous silica.

Influence of oxygen concentration on optical properties of semi-insulating polycrystalline silicon films

Optical properties of semi-insulating polycrystalline silicon (SIPOS) films were investigated over the wide region of wavelengths. The vibrational modes of Si-O-Si and Si-Si bonds were studied by IR and Raman spectroscopy. A pronounced effect of oxygen content on the measured spectra was observed. Optical constants of SIPOS films have been compared with those of amorphous silicon and glassy silicon dioxide and their values have been successfully interpreted in terms of the theory of effective medium. The results have shown that the amorphous character prevails in the as-deposited SIPOS films.

Analysis of the basic statistical properties of randomly rough curved surfaces by shearing interferometry

Shearing interferometry is employed for the analysis of basic statistical properties of rough curved surfaces. Using this method the root-mean-square values (standard deviations) of heights and slopes of the surface irregularities are determined. Moreover, autocorrelation lengths and functions of the surfaces mentioned are evaluated. A statistical analysis of randomly rough parabolic mirror collimators is performed by the method presented.

Deposition of metal nitrides by IBAD

Abstract Nitrides of metallic elements like Ti, Mo and Al were synthesized by ion beam-assisted deposition (IBAD). This technique was provided via dual ion beam deposition method in an apparatus based on two Kaufman ion beam sources. In our study an influence of the energy of assisting nitrogen ions (50–400 eV) and of the substrate temperature (up to 400°C) on the characteristics and properties of deposited thin films (roughness, thickness, chemical composition, structure, electrical and optical properties, etc.) was investigated. Different ex situ analytical techniques and measurements such as XPS, RBA, XRD, STM, profilometry, ellipsometry and other methods were applied. The composition of thin films prepared by the sputtering of Ti, Mo and Al targets was close to oxinitrides for all ion energies (fluxes). The nitrogen content in all films was increased by assisting ion bombardment; however, it sustained under their stoichiometric values. Structure of all thin films was generally dependent on ion beam energy and substrate temperature. The roughness and thickness (50–400 nm) of the films increased, respectively, decreased with ion energy (flux). Higher substrate temperature (400°C) substantially improved the adhesion of MoN films to silicon substrates. A significant influence of the assisting ion beam on electrical resistivity and index of refraction of Ti–N and Al–N films was observed.

Polarization anisotropy of photoluminescence from multilayer InAs/GaAs quantum dots

We present results of our study of photoluminescence (PL) from multilayer InAs/GaAs quantum dot structures grown by metal organic vapor-phase epitaxy and discuss them in terms of the envelope function approximation. The intensity of the component of the PL signal polarized in the plane parallel to the substrate is substantially higher than that corresponding to the perpendicular polarization. In addition, the former depends on the angle between the electric vector and the direction of elongation of the dots.

Optical characterization of nonabsorbing and weakly absorbing thin films with the wavelengths related to extrema in spectral reflectances.

In this contribution a new efficient modification of a method that enables us to perform the optical characterization of nonabsorbing and weakly absorbing thin films without using the absolute values of the reflectances measured is presented. Namely, this modification is based on determining the values of the wavelengths corresponding to touching the spectral dependences of the reflectances of the studied films measured for several angles of incidence with the envelopes of maxima and minima of these spectral dependences. By means of combining the explicit formulas containing the wavelengths mentioned and the suitable iteration procedure one can evaluate the values of the thicknesses and spectral dependences of the refractive indices of the films analyzed in reliable and precise ways.

Complete optical characterization of imperfect hydrogenated amorphous silicon layers by spectroscopic ellipsometry and spectroscopic reflectometry

In this paper the method based on interpreting the data measured within variable angle of incidence spectroscopic ellipsometry and spectroscopic reflectometry is used for the complete optical analysis of hydrogenated amorphous silicon layers deposited on silicon single crystal wafers. This method enables us to perform the analysis of these layers in a relatively wide spectral region because a new model of dispersion of the optical constants of the hydrogenated amorphous silicon layers was constructed. Moreover, the influences of both roughness and native oxide layer existing on the upper boundary of every silicon layer studied is respected at its analysis. The results obtained for a chosen sample of the hydrogenated amorphous silicon layer are presented.

Effect of composition changes on properties and defect structure of crystalline Sm-doped ZrO2

Polymorphous structure, electrical conductivity, absorption coefficient, refractive index, and mechanical characteristics of crystalline system ZrO2 + x Sm2O3 (x = 4–43 mol %) is investigated. Vickers microhardness is investigated by the well-known quasi-static indentation method. Plastic microhardness and the effective elastic modulus are studied by the depth-sensing indentation technique. Special attention is devoted to the ordered defect fluorite structure, pyrochlore phase Sm2Zr2O7, observed for x = 43 mol %. Potential applications of the investigated system are discussed.