PREPARATION AND PROPERTIES OF (CDS)(X)-(PBS)(1-X) THIN-FILM COMPOSITES

A modified chemical deposition process is employed for the preparation of thin-film (CdS)(x)-(PbS)(1-X) composites with 0.2 less than or equ al to x less than or equal to 0.8. Cadmium sulphate, lead acetate and thiourea are used as the basic source materials. The electrical conduc tivity is found to decrease with increasing composition parameter x up to 0.5 and increase for further increase in x. The composites are pol ycrystalline as is revealed from XRD and microscopic observations and show phases of both cubic and hexagonal CdS, cubic CdO and PbS, and te tragonal PbO and PbO2. Additional peaks of free elemental Cd and S hav e also been observed. For all the phases no significant variation in l attice parameters with x has been observed. The optical absorption stu dies show the presence of four well-defined absorption edges at approx imately 0.45 eV, 1.05 eV, 1.80 eV and 2.35 eV, at the same energies fo r all x values. The absorption coefficient is of the order of 10(4) cm (-1) and mode of band-to-band transition is of the direct type.