Heteroepitaxial growth of CuInS2 thin films on sapphire by radio frequency reactive sputtering

Abstract

Direct heteroepitaxial growth of uniform stoichiometric CuInS2 (CIS) thin films on sapphire (0001) substrates has been achieved by radio frequency reactive sputtering. X-ray ω–2θ scans reveal that the sputtered layers grow in a (112) orientation with a chalcopyrite structure. A rocking curve full width at half maximum of about 0.05° (180 arc sec) for the (112) peak demonstrates a nearly perfect out-of-plane arrangement of CIS (112)∥sapphire (0001). X-ray diffraction Phi scans further illustrate an excellent in-plane ordering of CIS [1̄10]∥sapphire (101̄0). The sputtered thin CIS epilayers had a smooth surface with a typical root-mean-square roughness of about 3.3 nm as evaluated by atomic force microscopy. The epitaxial growth of tetragonal CIS on hexagonal sapphire provides evidence that heteroepitaxial growth may be realized between structures of different symmetry, such as films of cubic or tetragonal structures on hexagonal substrates or vice versa.