DEPOSITION AND CHARACTERIZATION OF ZNXCD1-XS THIN-FILMS PREPARED BY THE DIP TECHNIQUE

ZnxCd1-xS (0 less than or equal to x less than or equal to 1) thin fil ms have been deposited by the dip technique on glass substrates. In th is method, a clean substrate was dipped into an alcoholic solution of the corresponding nitrates and thiourea and then withdrawn vertically at a controlled speed, and finally baked in a furnace.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 diffracto metric study suggests that for zinc atomic fraction x less than or equ al to 0.6 films prepared at a baking temperature of 500 degrees C are homogeneous with a hexagonal (wurtzite) structure. Increase in the pro portion of zinc in the starting solution is found to produce a decreas e in the lattice parameter. SEM studies reveal an increase in grain si ze 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 clearl y defined grains over this range. Values of bandgap obtained from opti cal absorption measurements as well as from spectral response of photo conductivity are in good agreement with each other and vary monotonica lly from 2.30 eV (CdS) to 2.69 eV (Zn0.6Cd0.4S) over the range 0 less than or equal to x less than or equal to 0.6. (C) 1998 Elsevier Scienc e S.A. All rights reserved.