Electrochemical growth and characterization of size-quantized CdTe thin films grown by underpotential deposition

Size-quantized thin films of CdTe were electrosynthesized onto Au(1 1 1) substrates by underpotential deposition (UPD) from an acidic aqueous solution of CdSO₄, and TeO₂. The electrodeposited thin films were characterized by scanning tunneling microscopy (STM), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and UV–vis absorption spectroscopy. The electrodeposition mechanism and the codeposition potential of CdTe were explored by cyclic voltammetry. The voltammetric analysis indicates that the electrodeposition of CdTe is a two-step codeposition process under the conditions of UPD. Morphological investigations demonstrate that the film growth proceeds via the formation of a few layers, growth of spherical nanoparticles on the overlayer and then continues by growth to form smooth spherical crystallites of CdTe. XRD results show that the growth of films are highly preferential with (1 1 1) orientation. Optical studies revealed blue shift in band gap energy due to quantum confinement.