Characterisation of Secondary Phases in Cu Poor CuInSe2: Surface and in-depth resolved Raman scattering analysis of polycrystalline layers

Abstract

AbstractThis work reports the surface and in-depth resolved Raman scattering analysis of polycrystalline CuInSe2 layers grown with different chemical composition, as function of the Cu to In content ratio (0.48 ≤ × ≤ 1.14). Measurements performed at the surface of the Cu-poor layers corroborate the formation of both Cu-poor Ordered Vacancy Compound (OVC) and CuAu ordered CuInSe2 phases for compositions corresponding to x ≤ 0.82 (OCV) and x ≤ 0.66 (CuAu), respectively. In-depth resolved measurements performed on the layers with lower Cu content have allowed observing a strong decrease with the depth of the intensity of the Raman peak from the chalcopyrite ordered CuInSe2 phase. This suggests a preferential formation of both OVC and CuAu ordered phases at the region close to the interface with the back Mo layer. On the other hand, the comparison between the spectra directly measured on the front and back surfaces of the layers -after removal of the layers from the Mo coated glass substrates- suggests also a worsening of the crystalline quality at the back region of the layers in the whole range of compositions.