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.------
Description:
This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD)
