STOICHIOMETRY CONTROL OVER A WIDE COMPOSITION RANGE OF SPUTTERED CUGAXIN(1-X)SE2

Films of CuGaxIn(1-x)Se2 (CGIS) have been grown by rf sputtering from stoichiometric single targets with different Ga/In ratios. Adjusting g rowth temperature and argon pressure we are able to deposit films with a wide range of Cu contents: From CGIS Cu-poor (16 at. %) to Cu2Se. R eevaporation of (Ga,In)2Se3 binaries is observed when substrate temper ature is increased at a constant argon pressure (20 mTorr). An increas e in Ar pressure from 5 to 150 mTorr at a growth temperature of 450-de grees-C, produces a decrease in Cu atomic percentage from 24% to 16% d ue to a preferential diffusion of Cu sputtered atoms in the plasma. Th e relevant film properties of the analyzed films are found to be ruled by the Cu content. Graded composition absorbers with adequate physica l properties for the fabrication of photovoltaic devices are grown wit h a proper choice of growth parameters.