Investigation of the structural and electro-optical properties of chemically deposited ZnS and CdS thin films and the thermoluminecence properties..

ABSTRACT INVESTIGATION OF THE STRUCTURAL AND ELECTRO-OPTICAL PROPERTIES OF CHEMICALLY DEPOSITED ZnS AND CdS THIN FILMS AND THE THERMOLUMINESCENCE PROPERTIES OF ZnS THIN FILMS OZTAS, MUSTAFA Ph. D. in P.E., University of Gaziantep Supervisor:Assoc.Prof.Dr.Refik KAYALI Co-adviser: Assoc.Prof.Dr.Ramazan ESEN December 1996, 140 Pages In this work, ZnS and CdS thin films have been developed onto glass substrates with different concentrations and at different substrate temperatures using the spraying pyrolysis method and electric, electronic, optic, structural, and thermoluminescence properties of these films have been investigated. The resistivities and Hall mobilities of the CdS and ZnS thin film samples were obtained using Van der Pauw method in the dark and under the illumination. The transit time of the CdS thin films was measured using the Haynes-Shockley experiment and the drift mobility of these films was calculated using these results. The carrier lifetimes of the CdS thin films was determined using photoconductive decay method. The trap density in CdS mthin films was calculated using the space-charge limited current method. The optical absorption coefficients of both the CdS and ZnS films were found from optical measurements and using these results the energy bandgap of these films was calculated. It was shown that both of these films have a wurtzite crystal structure by employing the X-ray diffraction powder method. Finally, the thermoluminescence property of ZnS thin films was examined. The trap density, activation energy and frequency factor values of these thin films were found from their glow curves. Then, the lifetime of the electrons trapped, using the values of activation energy and frequency factor, has been calculated. Keywords: Spray pyrolysis, thin film, ZnS and CdS IV