STUDIES ON CHEMICALLY DEPOSITED CDS1-XSEX MIXED THIN-FILMS

A solution growth process is employed for the deposition of CdS1-xSex thin film composites with 0 less than or equal to x less than or equal to 1. Cadmium acetate, thiourea and sodium selenosulphate were used a s the basic source materials. The samples were obtained at 55 degrees C in an alkaline medium and were characterised by optical and electric al characterisation techniques. The layer thickness is found to be dec reased as x is varied from 0 to 1. The optical absorption studies show ed a high coefficient of absorption (alpha = 10(4) cm(-1)) with an all owed direct type of transition. The optical energy gap decreases conti nuously (typically from 2.42 eV to 1.74 eV) as x is increased from 0 t o 1. For values of x between 0.5 and 0.8, two absorption edges have be en observed; one at approximately 2.40 eV corresponding to the fundame ntal optical transitions in CdS and the other decreasing continuously, which corresponds to the fundamental transitions in CdS1-xSex solid s olution. The electrical conductivity is found to decrease up to x = 0. 5 and to increase thereafter for further increase in x. The activation energy is more or less the same for all compositions and has no syste matic dependence on the composition parameter x.