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Information × Registration Number 0206U002383, 0103U001932 , R & D reports Title Defektive states interaction and photochromism of wide-gap materials popup.stage_title Head Dovhyi Yaroslav, Registration Date 15-05-2006 Organization Ivan Franko Lviv National University popup.description2 The nature and the energy structure of impurity and intrinsic defects including the formation of anisotropic impurity centres are determined in V-doped semi-insulating Cd1-xHgxTe (x=0,037) crystals which were grown by the Bridgman technique for the first time. From detailed analysis of the spectral dependence of the photodiffusion current data obtained for the different directions of light propagation in crystals as well as the impurity absorption spectra, we established that for the investigated crystals the anisotropic V2+ and V3+ centres are formed. Two mechanisms of the electron photogeneration from the ground impurity state to the conduction band (direct photoionization and auto-ionization from the excited state V2+ ions) are established. It is shown that the efficacy of the auto-ionization of electrons depends on the position of the excited state relative to the conduction band bottom. The photoinduced impurity centres are formed as a result of the illumination of the crystals with the light withenergy about 1.50 eV. The nature and photoionization energy of these photoinduced centres are determined. The scheme of the impurity and intrinsic defects energy levels in the energy gap of the investigated crystals is presented. Optical and photoelectric properties of CdTe:Ti crystals are studied. Structure of the impurity energetic levels and the intrinsic structural defects is elucidated. Nonstationary photo-induced current for the two crystallographic directions <100> and <110> and the case of two-wave interaction of IR radiation is studied for the above crystals. The nature of this current, which involves electronic transitions among the levels of real defects and the energy bands in crystal, is discussed. Anisotropy of the current is revealed to originate from anisotropy of the capturing centres for the charge carriers. The study of thermo-activation processes has enabled us to re-construct the structure of energy levels for the capturing centers in the PbWO4 crystal. At room temperature photoconductivity measurements were performed for PbWO4 crystals grown in different technology conditions. In the near band-edge region three bands of photo-ionization absorption (310 nm, 330 nm and 338 nm) are detected. Intensity of these bands depends on a crystal perfection and quality. The value of a photocurrent under the excitation within the 330 nm band depends on preceding irradiation of a PbWO4 crystal by a laser beam (lex=337 nm). The nature of defect centers related to the photo-ionization absorption bands is discussed. Product Description popup.authors popup.nrat_date 2020-04-02 Close