Photoeffects during cathodic electrodeposition of CdTe

Abstract The influence of illumination on the room-temperature cathodic electrodeposition of CdTe on n-Si was investigated using constant and pulsed illumination at 633 nm. The layers of CdTe were sufficiently thick that the observed cathodic photocurrent transients could be attributed to the deposit. The cathodic photocurrents exhibited a square root dependence on light intensity which is attributed to the amorphous nature of the CdTe deposit. Scanning electron microscopy and energy-dispersive X-ray analysis of the deposits showed that illumination during deposition at pH 0.5 produced a tellurium overlayer with a flower-like morphology. Illumination during deposition at pH 1.5, on the other hand, led to the formation of a nodular CdTe deposit on the smooth CdTe layer. These observations are rationalised by a reaction scheme for the cathodic photodecomposition of CdTe and subsequent chemical and electrochemical reactions.