Influence of indium doping on the properties of spray deposited CdS0.2Se0.8 thin films

Polycrystalline indium doped CdS0.2Se0.8 thin films with varying concentrations of indium have been prepared by spray pyrolysis at 300 °C. The as deposited films have been characterized by XRD, AFM, EDAX, optical and electrical resistivity measurement techniques. The XRD patterns show that the films are polycrystalline with hexagonal crystal structure irrespective of indium doping concentration. AFM studies reveal that the RMS surface roughness of film decreases from 34.68 to 17.76 with increase in indium doping concentration up to 0.15 mol% in CdS0.2Se0.8 thin films and further it increases for higher indium doping concentrations. Traces of indium in CdS0.2Se0.8 thin films have been observed from EDAX studies. The optical band gap energy of CdS0.2Se0.8 thin film is found to decrease from 1.91 eV to 1.67 eV with indium doping up to 0.15 mol% and increase after 0.15 mol%. The electrical resistivity measurement shows that the films are semiconducting with minimum resistivity of 3.71 × 104 Ω cm observed at 0.15 mol% indium doping. Thermoelectric power measurements show that films exhibit n-type conductivity.

Research highlights▶ Polycrystalline indium doped CdS0.2Se0.8 thin films with varying concentrations of indium have been prepared by spray pyrolysis at substrate temperature of 300 °C. ▶ Hexagonal crystal structure irrespective of indium doping concentration has been observed from XRD studies. RMS surface roughness of film is found to decrease with indium doping in CdS0.2Se0.8 thin films. ▶ The optical band gap energy and electrical conductivity are found to depend on the doping concentration of indium.