Investigations on chemically deposited Cd_(1-x)Zn_xS thin films with low Zn content

摘要

Thin films of Cd_(1-x)Zn_xS (0<=x<=0.8) were deposited on glass substrates by the chemical bath deposition technique. The as-deposited films were exposed to a stream of slowly flowing nitrogen at annealing temperature ranging 100-500 deg C. XRD patterns of as-deposited Cd_(1-x)Zn_xS over all mixture ratio values showed the cubic zincblende structure of which reflection peaks associated to (111), (220) and (311) planes were clearly identified. However, XRD characteristics of hexagonal wurtzite structure appeared at annealing temperature beyond 400 deg C. From scanning electron microscope, the as-deposited films were formed by different sizes of clusters of grains of which average grain size smaller than 50 nm was observed. The increase in mixture ratio value in the starting solution was found to produce a decrease in the grain size. Energy gap value of annealed films, which is obtained from optical transmission measurements, seems to shift to lower energy as the annealing temperature increases. Electrical sheet resistance of the films, performed in the darkness and under illumination conditions by using a halogen lamp, as a function of annealing temperature was also investigated. The variation of energy gap of thin films with annealing temperature was discussed by employing quantum size effect phenomena.