Chemical elaboration of well defined Cu(In,Ga)Se2 surfaces after aqueous oxidation etching Original Research Article

The present work is an attempt to prepare well defined surfaces of Cu(In,Ga)Se2 (CIGS) thin films in order to answer to basic questions about the relationship between bulk and surface composition. The approach is to use an oxidative etch with an aqueous bromine solution, known to lead to specular surfaces. The CIGS surface is then analyzed by mechanical profilometry, SEM and XPS, allowing for determination of the surface roughness and the nature of surface species. After short time bromine etch, a Se0 film is formed on the CIGS surface which can be completely removed by KCN treatment, leaving a CIGS specular surface. An highlight result is that under specific conditions, the surface composition is close to the stoichiometry of the Cu(In,Ga)3Se5 copper deficient phase. This is the first time that such a study is conducted on technology relevant thin polycrystalline CIGS film. It is expected that the method described will help conducting experiments (e.g. Angle resolved XPS, SIMS, etc.) with an improved resolution.