Microstructural and optical studies of CuO thin films prepared by chemical ageing of copper substrate in alkaline ammonia solution

In this paper, we report on the time-dependent development of cupric oxide films by chemical modification of copper substrates submerged horizontally in a room temperature 75 mmol/L ammonia solution at pH 11, over a period of nine days. Morphological and structural characterization of the oxide-substrate tandems were carried out by SEM-EDX and XRD, while the relative directional spectral absorptivity and reflectivity were determined by Vis-NIR spectrometry. The ageing process, controlling both the color and morphological structure of the predominately amorphous-CuO/Cu, has positively contributed to the enhancement of spectral absorptivity, while band gap values evolve from 1.29 to 1.39 eV for exposure times from 36 to 168 h. (C) 2014 Elsevier B.V. All rights reserved.