Structural and optical properties of Cu2O crystalline electrodeposited films

• DOI: 10.1016/j.tsf.2014.04.013
• Publication Date: 2014-04-13T09:33:18Z
• Authors: Iuri S. Brandt; Cesar A. Martins; Vinicius C. Zoldan; Alexandre D.C. Vi...; José H. Dias da S...; André A. Pasa
• Keywords: Electrodeposition; Optical properties; Thin films; Point defects; Texture; 02 engineering and technology; 0210 nano-technology; 530; Cuprous oxide

Abstract Cuprous oxide (Cu 2 O) films were electrodeposited on Ni/Si(100), Au/Si(100), and Si(100) substrates from aqueous solution at room temperature. The thicknesses of the films were varied in the range of 250 to 1250 nm. It was shown that at pH 10.00, an increase of just 1% can change the Cu 2 O texture from [100] to [111]. Atomic force microscopy reveals that Cu 2 O(100) and Cu 2 O(111) films present rounded and faceted grains, respectively. For the thinner films, it was also observed that the substrate has a strong influence on the Cu 2 O orientation. The Cu 2 O refraction index ( n ) and band gap energy ( E g ) were obtained from reflectance measurements. The Wemple and DiDomenico single oscillator model was applied to n data, and the dispersion energy E d of this model was addressed to describe the density of Cu vacancies in the Cu 2 O lattice. It was found out that the density of this kind of defect is higher for [111] oriented Cu 2 O films and decreases as a function of the film thickness. This analysis also indicated that the dynamics of formation of the Cu vacancy depends on the Cu 2 O lattice parameter. This parameter showed that Cu 2 O films are initially under compressive misfit stress, but at a critical thickness, the lattice parameter abruptly increases in order to relax the Cu 2 O lattice structure. This sudden transition is also observed in the E g data and is attributed to the enhancement of Cu–Cu internetwork interaction that is inversely proportional to E g .