Growth of dendritic structures on the surface of copper selenide thin films

Abstract

Dendritic structures have been extensively studied in the fields of photovoltaics, metallurgy, lasers, welding, and a variety of other applications in recent years. This paper discusses the formation of dendritic structures on the surface of pristine copper selenide thin films. These films were prepared by the Chemical Bath Deposition technique on the ITO substrate. A systematic investigation was carried out to detect the factors which initiate the filamentary growth. The pristine thin films were subjected to various laboratory conditions and the samples were periodically monitored using an optical microscope and SEM imaging. It was noticed that presence of HCl vapour activated the dendritic growth on the surface of pristine Cu2Se thin films. The XRD spectra of the dendritic film identified the presence of CuCl2 and SeCl4 in addition to Cu2Se and this was also confirmed in the EDS analysis. The XPS results revealed that dendritic growth was CuCl2 while the residual base film was rich in elemental Se. Based on these results a reaction mechanism was proposed which involved the disproportionation and decomposition of copper selenide thin film under the influence of HCl vapour. In the present study, it was found that the highly mobile copper atoms diffused from the copper selenide matrix in the presence of HCl vapour, leading to the formation of CuCl2 dendritic structure leaving the residual base film rich in elemental Se along with traces of SeCl4.