Thin films of ZnSe have been deposited onto glass substrates at 373 K by thermal evaporation technique. The X-ray diffractogram confirmed that ZnSe has cubic type crystal structure. The lattice parameters of thin films are almost matching with the JCPDS 5 - 552 data for Zinc Selenide. The transmittance and reflectance have been measured at normal and near normal incidence, respectively, in the spectral range 200 - 2500 nm. The dependence of absorption coefficient, α in the photon energy have been determined. Analysis of the result showed that films of different thicknesses, direct transition occurs with band gap energies ranges from 2.2 to 2.6 eV. Refractive indices and extinction coefficients have been evaluated in the above spectral range
Thin films of lead telluride (PbTe) of thicknesses ranging from 1000 Å to 2500 Å have been prepared by co-evaporation (three temperature) technique, onto precleaned amorphous glass substrates at various temperatures. The deposited samples were annealed and annealed samples were used for characterization. Resistivity of these samples was measured by four-probe technique as a function of thickness and temperature. Activation energy for charge transport have been evaluated and found in the range of 0.09 to 0.106 eV. Thermoelectric power has been measured and found to be positive indicating that the samples are p-type semiconducting material. Mobility variation with temperature has been estimated (evaluated) and correlated with scattering mechanism in the entire range of temperature studied. The X-ray diffraction analysis confirmed that films are polycrystalline having cubic structure cell and lattice parameters are reported.
Polycrystalline Lead Selenide Sulphide thin films have been deposited on glass substrate at 300 K by thermal evaporation technique. The different sets of samples of varying composition 'x' from 0.1 to 0.9 were deposited and annealed at reduced pressure of 0.1 micron for duration of 4 hours at temp (373) K. The material parameters determined are bulk resistivity 1.450 (Ohm-cm), mean free path 2820Å and carrier concentration 5.5 x 1012 per cm3. The estimated activation energy for heating cycles is larger as compare to cooling cycles. Fermi-energy determine from TEP study are within ranges between band gap energy and activation energy values.
Also the XRD study reveals that all the samples were polycrystalline having cubic FCC, cubic and tetragonal structure. The dependence of absorption coefficient ‘α’ on photon energy has been determined. The analysis of result so that for Lead Selenide Sulphide films of different composition, direct transition occurs with band gap energy in the range of 1.0 eV to 1.4 eV. Refractive indices and extinction coefficient have been evaluated and are in the range 1.20 to 4.80 and 0.005 to 0.0245 respectively. The compositions of films were analyzed using Energy Dispersive X-ray Analysis (EDAX). Also the grain size is determined from X-ray diffraction study. Most of the grain sizes are below 300 Å indicates that the film material exhibits nano structure. The SEM analysis indicates that the film is covered with large number of star shaped microgranuals. The size of the microgranuals increases with increasing ‘x’.
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