Evolution of Structural, Optical and Electrical Characteristics of Spin-Coated CdO Thin Films with the Gelation State of the Sol-Gel

摘要

The present work is intended to investigate the influence of the gelation state of the sol-gel on the properties of spin-coated cadmium oxide (CdO) thin films. The viscosity of the sol-gel increases at a slow uniform rate up to 5 days (break-off point) after which the rise becomes progressively more rapid and it attains saturation after 10 days of gelation. Films have been grown with gelation times of 2 days, 4 days, 6 days, 8 days, 9 days and 10 days. The visual characteristics of the films have been discussed in terms of the centrifugal force acting on the sol-gel. The sol-gel viscosity seems to be better suited to represent the gelation state of the sol-gel rather than the gelation time. The x-ray diffraction studies show that lower gelation times and lower sol-gel viscosities give rise to single crystalline CdO thin films while gelation times of 6 days and above (i.e. sol-gel viscosities of 2.92 x 10(-3) N s m(-2) and more) yield polycrystalline CdO thin films. The gelation state of the sol-gel has been found to have a strong bearing on the properties of CdO thin films, and highly conducting and transparent CdO thin films can be achieved by controlling the gelation state of the sol-gel and the results obtained have been reported.