Probing diffusion of In and Ga in CuInSe2/CuGaSe2 bilayer thin films by x-ray diffraction

Abstract The bilayer thin films of CuInSe 2 (CIS) and CuGaSe 2 (CGS) are fabricated by a molecular beam deposition (MBD) technique by sequential depositions of CGS followed by CIS and vise versa on Mo-coated soda-lime glass (SLG) and Mo/Al 2 O 3 -coated (Na blocking) SLG substrates. The thicknesses of CIS/CGS layers are adjusted to have the overall x =[Ga]/([In]+[Ga]) at approximately 0.4 similar to what is generally used in CIGS thin film solar cells. The growth temperature and the Cu-ratio y =[Cu]/([In]+[Ga]) of the CIS and CGS layers are systematically varied for Cu-rich ( y >1) and Cu-poor ( y