Crystal Research and Technology
Cryst. Res. Technol. 38, 83 (2003) - Abstract -

Electron irradiation-induced effects on optical spectra of (NH4)2ZnCl4: x Sr2+ single crystals

M. A. Gaffar, A. Abu El-Fadl*, and S. Bin Anooz*

Physics Department, School of Science and Engineering, The American University in Cairo, Cairo 11511, Egypt
*Physics Department, Faculty of Science, Assiut University, Assiut 71516, Egypt

Keywords    electron irradiation, ferroelectrics, ammonium zinc chloride, optical properties

The effect of electron-beam irradiation with different doses on optical constants of (NH4)2ZnCl4: x Sr2+ crystals with x=0.000, 0.020, 0.039, 0.087 or 0.144 wt% has been studied. The optical transmission in the energy range 3.4-6.4 eV was measured hence the absorption coefficient was computed as a frequency function. The absorption coefficient was also calculated as a function of electron-beam dose. Irradiation with e-beam did not affect the allowed indirect type of transition responsible for interband transitions of (NH4)2ZnCl4: x Sr2+ crystals. Values of the optical energy gap Eg and optical moment Ep for electronic interband transition of unexposed and (NH4)2ZnCl4: x Sr2+ crystals after e-beam exposure were deduced. The area under the absorption band at 5.30 eV was used to evaluate the effect of e-irradiation on optical parameters of samples with x=0.00, 0.020 or 0.039. A shift in the position and a nonmonotonic change in the intensity of this band with increasing e-beam dose was observed. Changes in the Eg value were used to evaluate the effect of e-beam exposure dose on (NH4)2ZnCl4: x Sr2+ samples with x=0.087 or 0.144. The obtained results were compared with those obtained for the same crystals after irradiation with different γ-doses.



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