EFFECT OF DOPING CONCENTRATION ON THE OPTICAL PROPERTIES OF NANOCRYSTALLINE Zn DOPED PbS THIN FILMS DEPOSITED BY CBD METHOD

Abstract

Nanocrystalline PbS and Zn doped PbS thin films have been deposited on glass substrates by chemical bath deposition (CBD) method. The as deposited thin films were found to be crystalline having cubic phase structure. The optical properties of the undoped and Zn doped PbS thin film have been studied. The chemically prepared Zn doped and undoped nanocrystalline PbS films have high absorbance in the UV-visible region. The linear nature of (αhν)2 vs (hν) plots of PbS thin films confirmed that the transition is direct and the optical band gap energy of PbS films is found to increase from 1.90 eV to 2.28 eV with decreasing crystallite size from 29 nm to 15 nm and these obtained band gap values are higher than the bulk value (0.40 eV). The increase in optical band gap supports the quantum confinement effect in the PbS thin films prepared by CBD technique. The optical band gap of Zn doped PbS films are found to increase with increase in dopant concentrations.

Optical and photoconductivity properties of Mn doped nanocrystalline PbS thin films deposited by chemical bath deposition method

“…Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. [1] The study of optical properties of nanocrystalline solids have become the topic of great interest from the theoretical and experimental research point of view [2]. As a consequence of quantum confinement, the continuum of states in the conduction and valance band are broken down into discrete states with an energy spacing relative to the band edge, which is approximately inversely proportional to the square of the particle radius [3], resulting in widening of the band gap as compared to the bulk.…”