Optical refractive properties and phonon spectra of Na2SO4 single crystal

Na2SO4 crystal was grown by slow evaporation method from an aqueous solution. Using the PXRD method, the crystal structure of Na2SO4 was investigated at room temperature, and it was found that the crystal belongs to the orthorhombic symmetry of the space group Fddd no. 70 with the following unit cell parameters a 5.8568 4 , b 12.2957 7 , c 9.809 1 , and V 706.52 8 3. The dispersion of the refractive indices of Na2SO4 crystal in the visible and ultraviolet ranges was measured at room temperature and the principle refractive indices of optical indicatrix were determined to be nX 1.4703, nY 1.4847, and nZ 1.47669 for the wavelength amp; 955; 500 nm. The first principle calculations of the phonon properties of the crystal were performed using the lattice dynamics method and DFPT approach. The polarized normal incidence reflection spectra of Na2SO4 crystal were measured in the infrared range 50 1300 cm amp; 8722;1 by using FTIR spectrometer and synchrotron radiation. The calculated reflection spectra of Na2SO4 crystal are in very good agreement with the experimental ones. In Na2SO4 crystal, the Reststrahlen band in the spectral range of 1120 1200 cm amp; 8722;1 is confirmed experimentally and theoreticall

Investigations of free electrons in doped silicon crystals derived from Fourier transformed infrared measurements and ab initio calculations

The reflection spectra of n and p type silicon crystals doped with phosphorus and boron were measured for the free carrier concentrations of 1.1 1015 cm amp; 8722;3 amp; 8722; 1.2 1020 cm amp; 8722;3 in the far and mid infrared range between 20 3000 cm amp; 8722;1 using synchrotron radiation and Fourier transformed infrared technique. Transmittance spectra could be measured for lower sample carrier concentrations from the range studied. The measured reflection spectra were fitted by using the Drude relation and the parameters of free electron conductivity electron effective mass m and momentum scattering time amp; 61556; were obtained for the n and p type doped silicon. Additionally, the calculations of the band electronic structure and the electric conductivity amp; 61555; of the crystals were performed in the framework of the density functional theory for different carrier concentrations and temperatures. The study main findings are 1 the substantial decrease of the momentum scattering time amp; 61556; and 2 the clear increase of the electron effective mass m with an increase of the carrier concentrations Nc for both n and p type doped silicon crystal

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 light intensity on the lifetime of carriers in silicon investigated by a photoacoustic method

AbstractThe paper presents experimental results of the lifetime of light induced excess carriers in the n−type silicon. The lifetimes of carriers of silicon crystals were analysed as a function of the intensity of light illuminating the sample. As a measurement method of the lifetime of carriers, the photoacoustic method in a transmission configuration with different surfaces was used. The dependence character was next analysed in the frame of the Shockley Reed Hall statistics in approximation of the light low intensity.</jats:p

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