Influence of sputtering power on composition, structure and electrical properties of RF sputtered CuIn1-xGaxSe2 thin films

In this study, Cu(In1-xGax)Se-2 (CIGS) thin films were deposited at room temperature by one step radio frequency (RF) magnetron sputtering process. An one-stage vacuum annealing process without selenization was performed to improve properties of the films. Influences of sputtering power on composition, structure and electrical properties of the as-deposited and annealed films were investigated. As the sputtering power not exceeding a proper power of 100 W, the as deposited and annealed films show near stoichiometric composition and polycrystalline chalcopyrite structure. The annealed films exhibit almost the same composition as the as-deposited ones. All the sputtered and annealed films exhibit uniform and compact surface morphology without peeling and cracking. The electrical conductivity measured in 50-290 K range reveal that the 50 W and 100 W deposited films exhibit metal and semiconductor character, respectively. The 100 W deposited film present data consist with thermoionic emission at high temperatures of 200-290 K. However, Mott law with the variable range hopping mechanism is predominant in the low temperature region. (c) 2012 Elsevier B.V. All rights reserved.