Microstructural investigations on CdTe thin films electrodeposited using high current pulses

Abstract

CdTe thin films were electrochemically deposited over FTO-coated glass substrates by singular unipolar current pulses of high magnitude. A wide range of periodic current pulse parameters was investigated in CdTe thin film deposition and the growth properties of the deposited film were determined as a function of variables viz. applied current density, average current and ON/OFF pulse duration and the conditions were optimized for stoichiometric CdTe film growth. A detailed investigation has been carried out to understand the effect of pulse parameters on CdTe growth phases and film microstructure. As evidenced by the diffraction patterns of pulse electrodeposited CdTe films mean current density of 0.36 mA/cm 2 represents an upper limit to form crystalline—CdTe film without secondary phases. Increase in pulse current show inclusion of secondary growth phases. A highly oriented cubic phase was obtained at low current pulse, due to low nucleation rate and surface diffusion of adions on the substrate to growth sites. The crystalline structure and morphology of films were analyzed using powder X-ray diffraction and scanning electron microscopy suggest that OFF time contributes more on the grain size, whereas ON time affects the rate of deposition and grain morphology.