Photoelectrochemical properties of size-quantized CdS thin films prepared by an electrochemical method

Size-quantized CdS thin films were prepared by sequential underpotential de position of S and Cd on Au(lll). The prepared films in an aqueous solution containing triethanolamine as a sacrificial electron donor showed n-type ph otoelectrode behaviors. Action spectra of anodic photocurrents were red-shi fted with an increase of the film thickness toward characteristic values of those of bulk materials. The energy gap of the film determined from the ac tion spectra showed a remarkable tendency of decrease with an increase of t he film thickness up to 3.5 nm. Beyond 3.5 nm the rate of decrease with inc rease in the film thickness declined. An energy gap value characteristic of bulk materials was obtained with CdS films greater than 6.8 nm.