Physical vapor deposition of hexagonal and tetragonal CuIn5Se8 thin films

Hexagonal and tetragonal CuIn5Se8 thin films have been successfully prepared by physical vapor deposition. A hexagonal CuIn5Se8 thin film was obtained via the reaction of (Cu+Se) and (In+Se) layers. This hexagonal film had a layered structure with a lattice spacing of approximately 16 angstroms, corresponding to fivefold close-packed stacking of Se. With an alternative deposition process using (CuInSe2) and (In2Se3) layers, a tetragonal CuIn5Se8 thin film was obtained. The tetragonal film had a columnar structure with a lattice spacing of 3.3 angstroms, corresponding to the cubic close-packed stacking of Se. As evident from examination of the Cu2Se-In2Se3 pseudo-binary system phase diagram, hexagonal CuIn5Se8 is a stable phase and tetragonal CuIn5Se8 is metastable. The growth mechanism of the hexagonal and tetragonal phase CuIn5Se8 thin films is discussed from a crystallographic point of view.