Growth of CuInSe2 by two magnetron sputtering techniques

The results of experiments characterizing CuInSe2 deposition by reactive magnetron sputtering and by a hybrid sputtering and evaporation technique are presented. Both techniques produce films with chemical and structural properties comparable with those commonly used for polycrystalline CuInSe2-based solar cells. The reactive sputtering technique produces films with compositions ranging from copper rich to indium rich with near-stoichiometric selenium contents at low temperatures. Indium-rich films cannot be produced at temperatures above about 400°C. The hybrid process produces films over a large composition range at growth temperatures up to 450°C. Film compositions are uniform across 25 mm substrates to within ±1 at.% and non-uniformities can be directly related to the deposition geometry. For hybrid films, the selenium flux is shown to play a major role in determining both the selenium and the indium contents of the films at elevated temperatures. A coupled In-Se desorption mechanism which is inhibited by the presence of large amounts of excess selenium is proposed to explain the latter data. The substrate material is shown to affect strongly the film chemistry. Films deposited on copper show a higher copper content due to diffusion of the substrate material into the film during growth. Layers deposited by the hybrid process on molybdenum exhibit lower indium and higher selenium contents than films on glass at all temperatures examined. Finally, copper, indium and selenium diffusion into molybdenum substrates was observed at all growth temperatures.