X-ray photoelectron spectroscopic studies of oxygen chemisorption on thick films of photoconducting cadmium sulfide

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Abstract
X‐ray photoelectron spectroscopic studies of highly photosensitive thick films of cadmium sulphide have been carried out which reveal the appearance of a complex triplet structure (S2p) spread over about 20 eV with peaks centered at binding energy values of 162.6, 172.8, and 179.7 eV. Using the available literature data, the S2p peak at 162.6 eV is interpreted to originate from S−− ions, the one at 172.8 eV from the SO−−4‐ like species and that at 179.7 eV from SO2‐like species, the latter two being formed on the surface due to the preferential bonding of chemisorbed oxygen with sulphur. After thermal desorption, the films exhibit no photosensitivity and there is a substantial reduction in the intensities of 172.8‐ and 179.7‐eV peaks. A close link between the existence of SO−−4 and SO2 (adsorbed) species and photoconductivity is clearly manifested.