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

The monitoring circuit of photovoltaic system

W pracy przedstawiono budowę systemu fotowoltaicznego znajdującego się Laboratorium Optoelektroniki Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej. System służy celom dydaktycznym i rozwojowym z zakresu fotowoltaiki. System wzbogacono w układ monitorowania stanu pracy oraz oprogramowanie do gromadzenia danych pomiarowych. W pracy zaprezentowano również przykładowe aplikacje wykorzystane do analizy danych eksperymentalnych. Rzeczywisty zysk energetyczny porównano z zyskiem energetycznym otrzymanym w wyniku symulacji za pomocą programu ‘Polysun’.The paper presents the photovoltaic system placed in The Laboratory of Optoelectronic, Division of Electronics and Computer Sciences, Technical University of Koszalin. The system is used for didactics and research tasks on the field of photovoltaics. The monitoring circuit and the application for collecting data have been added to the system. The examples of the applications used for analysis of the experimental data are also presented. The real energetic yield was compared with energetic yield obtained from simulation by ‘PolySun’ application

Influence of plasma waves on the photoacoustic and piezoelectric spectra of semiconductors

This paper presents results of numerical studies of the influence of plasma waves in semiconductor samples on their photoacoustic and piezoelectric photothermal spectra. This influence was examined theoretically with the newly derived compact model describing the spatial distribution of the instantaneous temperature field in the semiconductor samples in the presence of plasma waves. This model enabled computations of the photoacoustic and piezoelectric spectra in the front and rear experimental configurations and determination of the influence of plasma waves on them

1D or 3D spatial temperature distribution- comparison

This paper shows the comparison of the results of computations of the spatial distribution of the temperature in the sample and the spectra of the piezoelectric signals in 1D and 3D thermal models. The considerably different temperature distributions in the sample observed for short thermal waves, when the sample is thermally thick, and a narrow beam of the exciting light did not cause considerable changes of the spectra of the piezoelectric signal. These results are the evidence that 1D approach can be successfully applied for the interpretation of the piezoelectric spectra obtained in the piezoelectric spectroscopy method

Comparison of plasma wave models in photoacoustics

Plasma wave effect describes the influence of diffusion and irradiative recombination processes of excess carriers on the instantaneous temperature distribution in the sample. This temperature field is responsible for a series of effects observed experimentally. The most important element for the computations of the plasma wave effect is the formula for the spatial temperature distribution in the sample. The aim of this paper was: to investigate and compare different temperature distribution formulae, derive another temperature distribution formula with the thermal wave interference method of Benett and Patty and simplify the notations to make the formula more convenient and practical

Determination of a quantum efficiency of AII^{\rm II}–BVI^{\rm VI} compounds on the basis of photoacoustic spectra

The method of determination of the quantum efficiency $\eta$ of irradiative relaxation processes in semiconductors is introduced and discussed. The correlation of the amplitude photoacoustic spectra in the high absorption region with the annealing process is used to estimate the values of $\eta$. The values of $\eta$, both for as grown and annealed crystals were determined and have been discussed. The results are presented for microphone and piezoelectric detection methods