Publication: Study of Surface Defects on Co-Doped TiO2 Thin Films Deposited by Spray Pyrolysis
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2016-07
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MDPI
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Abstract
Surface photovoltage (SPV) spectroscopy is a powerful tool for studying electronic defects
on semiconductor surfaces, at interfaces, and in bulk for a wide range of materials. Undoped and
Cobalt-doped TiO2 (CTO) thin films were deposited on Crystalline Silicon (c-Si) and Flourine doped
Tin oxide (SnO2:F) substrates by chemical spray pyrolysis at a substrate temperature of 400 ˝C.
The concentration of the Co dopant in the films was determined by Rutherford backscattering
spectrometry and ranged between 0 and 4.51 at %. The amplitude of the SPV signals increased
proportionately with the amount of Co in the films, which was a result of the enhancement of the
slow processes of charge separation and recombination. Photogenerated holes were trapped at the
surface, slowing down the time response and relaxation of the samples. The surface states were
effectively passivated by a thin In2S3 over-layer sprayed on top of the TiO2 and CTO films.
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Masinde Muliro University of Science and Technology