Results on the thermal decomposition of chemically deposited SnS thin
films to sub-stoichiometric and near-stoichiometric SnO2 thin films on
glass substrates are presented. The SnS-to-SnO2 conversion is illustr
ated using X-ray diffraction spectra, X-ray photoelectron spectroscopy
(XPS), optical transmittance spectra and electrical characteristics.
SnS thin films of approximately 0.7 mu m thickness and appearing deep
red in transmission could be converted to transparent SnO2-x films at
temperatures above 325 degrees C. It requires about 20 h at 350 degree
s C, 2 h 45 min at 400 degrees C, 30 min at 450 degrees C or 10 min at
500 degrees C for the near-complete conversion, but a relatively thin
ner film (of 0.25 mu m) requires only about 30 min for the conversion
at 400 degrees C. At the threshold of the transformation, the films sh
ow sheet resistance of about 10(4) Omega/square, which increases upon
prolonged annealing to about 10(9) Omega/square for 18 h annealing at
500 degrees C. The ratio of dark sheet resistance to photo sheet resis
tance is about ten for SnS films under 600 W m(-2) tungsten-halogen li
ght and is about 10(3) for SnO2 films.