Pulsed laser deposition and characterization of epitaxial CuInS2 thin films on c-plane sapphire substrates

The epitaxial growth of CuInS2 thin films on single-crystal sapphire (0 0 0 1) substrates was first attempted by using pulsed laser deposition. A highly dense CuInS2 ceramic target with chalcopyrite structure was prepared by sintering high-purity (5N) powders in vacuum at 960 °C for an hour. CuInS2 thin films deposited at various temperatures all grew in a (1 1 2) preferred orientation, suggesting a three-dimensional island-like growth mechanism. When deposited at 700 °C, epitaxial growth of CuInS2 films on c-plane sapphire was achieved with an out-of-plane orientation of CuInS2 (1 1 2)|| sapphire (0 0 0 1) and in-plane orientation of CuInS2[1¯10]‖sapphire(101¯0). A typical rocking curve half width of 0.17° demonstrates a high degree of crystallinity as well as excellent alignment of the CuInS2 films along [2 2 1], whereas in-plane two domains rotated by 180° with respect to each other are found coexisting in the epilayers. High-quality epitaxial thin films will allow further research into the fundamental properties of CuInS2 absorber layers, which will eventually help to improve conversion efficiencies of CuInS2-based solar cells.

► A highly dense CuInS2 ceramic target with chalcopyrite structure was sintered in high vacuum. ► Epitaxial growth of CuInS2 thin films on sapphire (0 0 0 1) substrates was achieved by PLD at 700 °C. ► Epitaxial relationship is CuInS2 (1 1 2)|| sapphire (0 0 0 1) while CuInS2[1¯10]‖sapphire(101¯0). ► A rocking curve half width of 0.17° demonstrates an excellent out-of-plane ordering of the films. ► In-plane two domains rotated by 180° to each other are found coexisting in the epilayers.