Pb dopant induced changes in structural, optical and electrical properties of CdSe thin films

Abstract

Thin films of Pb doped CdSe at 1% and 5% dopant concentrations have been prepared by thermal evaporation technique using inert gas condensation method on glass substrates. The effect of Pb doping on structural, optical and electrical properties of CdSe thin films has been studied. Elemental composition of the thin films has been analyzed using Energy Dispersive X-ray analysis (EDX) spectra. Transmission electron microscope (TEM) images show the spherical nature of the nanoparticles. X-ray diffraction spectra indicate the presence of hexagonal phase of CdSe in undoped and Pb doped CdSe thin films, and formation of cubic phase of PbSe with the increase in amount of Pb dopant. A decrease in the band gap with increase in Pb doping in CdSe lattice has been observed due to the formation of band tails in the band gap and increase in crystallite size after doping. The photoluminescence (PL) spectra of thin films have been studied and enhancement in the PL intensity is observed after Pb doping. The dark conductivity of the prepared thin films has also been studied and two types of conduction mechanisms have been observed. Hall measurements indicate change in conduction mechanism from n-type to p-type after Pb doping in CdSe.