Zinc sulphide (ZnS) thin films with both n- and p-type electrical conductivity
were grown on glass/fluorine-doped tin oxide-conducting substrates from
acidic and aqueous solution containing ZnSO4 and (NH4)2S2O3 by simply
changing the deposition potential in a two-electrode cell configuration. After
deposition, the films were characterised using various analytical techniques.
X-ray diffraction analysis reveals that the materials are amorphous even after
heat treatment. Optical properties (transmittance, absorbance and optical
bandgap) of the films were studied. The bandgaps of the films were found to be
in the range (3.68–3.86) eV depending on the growth voltage. Photoelectrochemical
cell measurements show both n- and p-type electrical conductivity
for the films depending on the growth voltage. Scanning electron microscopy
shows material clusters on the surface with no significant change after heat
treatment at different temperatures. Atomic force microscopy shows that the
surface roughness of these materials remain fairly constant reducing only
from 18 nm to 17 nm after heat treatment. Thickness estimation of the films
was also carried out using theoretical and experimental methods. Direct
current conductivity measurements on both as-deposited and annealed films
show that resistivity increased after heat treatment.