Optical and transport properties of CdS1-xTex alloyed thin films

A good deal of information regarding synthesis, optical and electrical tran sport properties of the chemically grown CdS1-xTex thin film structures is presented. Growth of these films depend upon various preparative parameters and deposition conditions such as temperature, pH, time, concentration, sp eed of the mechanical churning etc and the reaction kinetics suggests that the films grow in two different phases; an initial quasi-linear and second a saturation. The as-deposited films are crystalline over the whole range o f the composition parameter and both CdS and CdTe are deposited as a mixtur e of the hexagonal wurtzite and cubic zinc blende structures (hexagonal bei ng dominant. The solid solution is observed for hexagonal phase in the 0 le ss than or equal to x less than or equal to 0.1 and 0.9 less than or equal to x less than or equal to 1 regions. In the middle range (0.1 less than or equal to x less than or equal to 0.9), separate phases of both CdS and CdT e have been detected. Optical absorption studies revealed a high absorption coefficient (10(4) - 10(5) cm(-1)) with direct type of transition. The est imated bandgap decreased almost linearly with the high composition paramete r of ,x. The room temperature electrical conductivity is found to be increa sed initially with the composition parameter (0 less than or equal to x les s than or equal to 0.1) decreased for a further increase in x (0.1 less tha n or equal to x less than or equal to 0.8) and again increased for higher T e content in CdS. The material exhibits both grain boundary scattering limi ted and a variable range hopping conduction mechanisms. The thermoelectric power is negative showing n-type behaviour of the samples. Both carrier con centration (n) and mobility (mu) were computed and found to be sensitive fu nctions of temperature.