A Study of The Electrical And Optical Properties of Zno Thin Films Spray Pyrol Ysed From Zn(C2H302)2 2H20

Abstract

Investigations have been carried out on spray pyrolysed undoped and indium doped ZnO thin films for the thickness range 700-4000 A. The undoped ZnO thin films were found to be nonstoichiometric but homogeneous and polycrystaline in structure as confirmed by the structural studies. The virgin films were highly resistive whereas vacuum annealed films are. good transparent conductors. Aging effect has been observed within the first 15 days of the film fabrication. Size effect has been observed below 1500 A. The doped film (ZnO: In) showed higher carrier concentration and Hall mobility. The effect of successive post-deposition ~eat treatments in air and vacuum has been studied. It has been observed that the heat treatment in different ambients have remarkab 1 e effects on the electrical transport properties. Due to the successive heat treatment operation, the carrier concentratio~ - changes from 1015 - 1018 cm-3 and mobility changes from 4 - 16 cm2/vs·. Oxygen chemisorption-desorption mechanism were found to play an important roie to control the electronic properties. Various grain boundary and energy band parameters have been calculated by using conventional extrinsic semi conductor theory and grain boundary trapping models. The samples were non-degerate at room temperature, and the Ha 11 mobility was found to be modu I ated by the grain boundary potential barrier height via the samples temperature. For ZnO thin films two distinct scattering process viz the grain boundary scattering and the piezoelectric scattering are found to play a predominant role in limiting the Hall mobility.------