Deposition and characterization of Zn xCd 1− xS thin films prepared by the dip technique

Abstract

Zn x Cd 1− x S (0≤ x≤1) thin films have been deposited by the dip technique on glass substrates. In this method, a clean substrate was dipped into an alcoholic solution of the corresponding nitrates and thiourea and then withdrawn vertically at a controlled speed, and finally baked in a furnace. X-ray diffractometric study suggests that for zinc atomic fraction x≤0.6 films prepared at a baking temperature of 500°C are homogeneous with a hexagonal (wurtzite) structure. Increase in the proportion of zinc in the starting solution is found to produce a decrease in the lattice parameter. SEM studies reveal an increase in grain size with x up to a value of 0.6. For x>0.6, the films appear to have an amorphous character, as no distinguishable peaks can be seen in the X-ray diffractograms. The SEM micrographs also do not show any clearly defined grains over this range. Values of bandgap obtained from optical absorption measurements as well as from spectral response of photoconductivity are in good agreement with each other and vary monotonically from 2.30 eV (CdS) to 2.69 eV (Zn 0.6Cd 0.4S) over the range 0≤ x≤0.6.