PREPARATION AND PROPERTIES OF CDS-BI MIXED THIN-FILMS

The preparation details and a few of the properties of the CdS:Bi mixe d thin films dependent on Bi/Cd molar ratio (r = 0 to 0.7) have been e xplored. A chemical deposition process set for its various deposition conditions is employed for this purpose and the deposition was carried out in an alkaline medium (pH = 9.5 +/- 0.2) at 85 +/- 2 degrees C. T he deposits appear smooth, tightly adherent, uniform and diffusely ref lecting. The colour of the deposit changes from an orange red to yello wish brown and the terminal thickness decreases continuously as r is c hanged from 0 to 0.7. The samples are polycrystals (up to r = 0.3) of cubic and hexagonal cadmium sulphide and an orthorhombic bismuth trisu lphide. The lattice spacing d values and lattice constants of bath the phases are in good consonance with their literature values. The depos its tend towards amorphous as r is increased beyond 0.3. The scanning electron micrographs also support these observations. The optical stud ies show decrease in the band gap with increase in r. The absorption c oefficient is high (similar or equal to 10(4) cm(-1)) and mode of tran sition is direct. The absorption edge is found to be broader and the b roadening increases further with increasing value of the parameter r.