Mat. Res. Bull., Vol. 17, pp. 279-286, 1982. Printed in the USA. 0025-5408/82/03279-08503.00/0 CopyriKht (c) 1982 Pergamon Press Ltd. PREPT~-q±\TIOI~ OF LEAD IODIDE FILMS BY IODiNATION OF CHEMICALLY DEPOSITED LEAD SULPHIDE FILMS T. K. Chaudhuri and H. N. Acharya Department of Physics Indian Institute of Technology Kharagpur - 721 302 IND IA (Received March 9, 1981; Refreed) ABSTRACT A method of preparation of PbI 2 films by iodination of chemically deposited PbS films is described. The X-ray characterization of these films show that they are poly- crystalline in nature and the crystallites are preferen- tially oriented with c-axis perpendicular to the plane of the substrates. The analysis of the diffuse reflec- tance measurements performed on material scraped off the substrates yielded a forbidden energy gap of 2. 34 eV in conformation with the results of pure PbI 2 powder. The transmittance spectra of these films, in th~ wavelength range 400 to 600 nm, revealed a characteristic strong absorption edge at about 510 nm and a hump at about 490 nm. On the basis of the changes in conductance of PbS film during iodine treatment a mechanism of iodina- tion has been proposed. INTR 0DUCT ION Lead iodide is a prospective material for non-silver ~>hotography whose optical (I-4), photoconducting (5-8), photo- craphic (9-12) and other properties (13-16) have been studied ~×tensively. Thin films of lead iodide have the potentiality of being utilized in high resolution photography (9), holography (17), submicrosecond imagery (18) and metal micropattern genera- tion for production of integrated circuits (19). Add-on facility is considered to be a special feature of the lead iodide imaging systems. Sensitized lead iodide films are envisaged (II) to be a substitute for conventional silver halide photographic films. Thin films of lead iodide are generally made by the vacuum evaporation technique. An alternative method of preparing ]ead iodide films by a chemical process was briefly reported by Chaudhuri, Bose and ~charya (20). This method is amenable to 279