About the optical properties of oxidized black silicon structures

Abstract The paper deals with the optical and morphological properties of thermally oxidized black silicon (OBSi) nano-crystalline specimens produced by the surface structure chemical transfer method (SSCT). This method can produce a nano-crystalline Si black color layer on c-Si with a range of thickness of ∼50 nm to ∼300 nm by the contact of c-Si immersed in chemical solutions HF + H2O2 with a catalytic mesh. We present and discuss mainly the photoluminescence properties of both polished c-Si and OBSi structures, respectively. The similar photoluminescence (PL) behaviors recorded at liquid helium (6 K) and room temperatures on both polished crystalline Si and OBSi samples, respectively, indicate the similar origin of recorded luminescence light. As the positions of PL maxima of OBSi structures are mainly related to the size of Si nanocrystallites and SiO(x), we therefore suppose that the size of the dominant parts of the luminated OBSi nanostructure is pre-determined by the used polishing Si procedure, and/or the distribution function of the number of formed crystallites on their size is very similar. The blue shift of both PL spectra reaching almost value of 0.40 eV observed after the decrease of the sample temperature to 6 K we relate also with the change of the semiconductor band gap width.