Measurements of optical absorption and photoconductivity (steady state, frequency dependent, time dependent) were made on an n-type CdTe single crystal and on an evaporated CdTe thin film. For the single crystal the standard steady state photoconductivity showed an intrinsic peak at 1.4 eV. The lifetime calculated from ac photoconductivity measurements was in the range (1.1 - 5) s. The lifetime showed a minimum at exactly the same photon energy at which the photocurrent was maximum. The decay time was always longer than the lifetime. Optical absorption measurements revealed a direct transition and an optical gap of 1.47 eV at 80 K. Polycrystalline thin films of CdTe were grown by vacuum evaporation on glass substrates held at . The films showed a peak in the spectral distribution () curve at 1.65 eV. Direct and indirect transitions were again observed and found to be temperature dependent.
The problem of structure investigation of thin films using laboratory XRD diffraction intensities was discussed as a matter of debate. Is the variation in relative intensities of the diffraction patterns due to crystallographic preferred orientation, lattice defects or both? The answer to this question shows a discrepancy in the literatures. The present work is an attempt to propose a possible approach to judge the most probable answer. Thin films of SnO 2 were prepared by spray pyrolysis technique using solution of different SnCl 2 concentrations (molarity); at fixed substrate temperature and deposition time. The theoretically calculated integrated intensities together with the experimentally obtained and calculated XRD data (relative intensities, texture coefficients and profile analysis) were considered together in order to get the proper picture of the structure characteristics of the prepared films. The complete picture can be assembled by integration and correlation of all the crystallographic information that are extracted from the diffraction pattern including not only the observed intensities but also the size/strain analysis and lattice parameters.
The density of states (DOS) near the Fermi level is studied for hydrogenated amorphous silicon (a‐Si: H) thin films using the space charge limited current technique (SCLC). Experiments using films of different thicknesses show that surface states significantly contribute to the DOS. Investigations of both front and back contacts indicate that the first deposited layers imply DOS higher than the rest of the film. The study also shows that the film characteristics are dominated by the top electrode.
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