Growth and characterization of spray deposited lead zinc sulphide thin films

Abstract

Ternary thin films are attractive for many applications due to their band gap tunability. In the present study, the stoichiometric n-PbxZn1-xS (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) were deposited on glass substrates using spray pyrolysis technique. The structural, optical and electrical studies have been made in order to understand the band gap tunability of prepared films. The optical band gap energy of PbxZn1-xS thin films varied from 0.40 eV to 3.54 eV and the transition has been changed from indirect to direct with different Pb: Zn mole fractions. It has been observed that the complete indirect to the direct transition of energy band gap occurred in PbxZn1-xS (x≤0.5) thin films. The resistivity and activation energy of the films were increased with an increase in the band gap indicating the formation of a mixed films of PbS and ZnS in the ternary phase. Photoconductivity of the films was thoroughly studied and the possibility of using the lead zinc sulphide thin films as UV-IR photo detectors was investigated. Heterojunctions p-Si/n-PbS, p-Si/n-ZnS and p-Si/n-PbxZn1-xS were fabricated considering their usefulness in the fabrication of optoelectronic devices. A detailed electrical characterization of these heterojunctions was performed to understand the conduction mechanism in operation and also to determine various technically important parameters. The results confirmed the formation of a continues solid solution of PbS and ZnS in the ternary phase which can be a suitable candidate for optoelectronic applications.