Optical absorption spectra in the far infrared range and phonons of CdSe1 xTex thin films

Optical reflection spectra of CdSe1 xTex thin films deposited on quartz substrates are measured using the synchrotron radiation in the spectral range of 20 500 cm amp; 8722;1. The absorption bands of CdSe, CdTe, CdSe0.75Te0.25, CdSe0.5Te0.5, and CdSe0.25Te0.75 films are localized in the range of 20 220 cm amp; 8722;1. The imaginary parts of the dielectric function amp; 949;2 amp; 955; amp; 8722;1 of CdTe1 xSex crystals calculated in the framework of the density functional theory are in good agreement with the experimental reflection spectra of CdTe1 xSex films. The eigenvectors of the dynamical matrix CdTe1 xSex crystals are analyzed for several phonon modes to understand the difference between the frequency dependences of the calculated vibration density of states and the imaginary part of dielectric function amp; 949;2 amp; 955; amp; 8722;1 . Small features of the experimental reflective spectra of CdSe1 xTex films in the ranges 50 70 cm amp; 8722;1 and 80 120 cm amp; 8722;1 are explained using the analysis of results of the molecular dynamics. During comparative molecular dynamics calculations, it was found that the vibration density of states of a thin CdTe slab with a surface to volume number of atoms relation of NS NV 0.2, experienced a redshift of approximately 30 cm amp; 8722;1. This shift was observed in comparison with the CdTe single crysta

The optical properties of In2S3 films in the far infrared spectral range

Optical reflection spectra of In2S3 thin films 180 730 nm deposited on glass substrates are measured by infrared spectroscopy using the synchrotron radiation of BESSY II storage ring in the spectral range of 30 8000 cm amp; 8722;1. The aim of the study is to find the influence of different substrate and post annealing temperatures on the electron and phonon systems of In2S3 films deposited on glass. Clear features in the reflectance spectra for the studied films have been found mainly in the phonon excitation range 100 400 cm amp; 8722;1. The experimental dielectric functions amp; 949; amp; 969; of In2S3 films are found to be in good agreement with the calculated ones obtained for In2S3 crystals within the density functional theory. The dielectric functions amp; 949; amp; 969; of the films in the range of 100 400 cm amp; 8722;1 depend substantially on the post annealing temperature. This indicates a transition of the film from the amorphous to the crystalline state. The thorough analysis of the frequency dependence of the reflection coefficient R amp; 969; and optical conductivity amp; 963; amp; 969; in the wavenumber range of 30 130 cm amp; 8722;1 allowed us to reveal the distributed electron states in In2S3 film

Dielectric dispersion of SBN crystals in the spectral range of the visible light and ultraviolet

Dyspersja przenikalności dielektrycznej (funkcje pseudo-dielektryczne) (E) = (E) + i(E) kryształów SrxBa1-xNb2O6 (SBN) została zmierzona w temperaturze pokojowej dla pięciu współczynników zawartości atomów Sr (x = 0,40; 0,55; 0,61; 0,65; 0,75) oraz Ba (1-x) przy pomocy spektroskopii elipsometrycznej z wykorzystaniem promieniowania synchrotronowego w zakresie energii fotonów E = 1,3 – 10 eV. Uzyskane widma (E) dla SBN są bardzo zbliżone do analogicznego widma kryształu LiNbO3, w którym oktaedryczne grupy NbO6 są odpowiedzialne za osobliwości zależności (E). Przeanalizowano zmiany charakterystyk dyspersyjnych SBN wraz ze zmianą współczynnika x. Ustalono, że zależność części urojonej przenikalności SBN od współczynnika x jest o charakterze ekstremalnym, nieliniowym