RESUMO
We investigated the growth, structural and optical characteristics of CuGaSe2 thin films prepared with the selenium reaction. Metallic precursor layers from Cu0:5Ga0.5 and Cu0.8Ga0.2 alloy targets were prepared on a sodalime glass substrate by using DC magnetron sputtering, and then annealed to form CuGaSe2 in a rapid thermal process (RTP) with selenium radicals generated by a thermal cracker. The base and sputtering pressures were < 5 x 10(-7) Torr and 30 mTorr, respectively. At ambient temperature, the precursors from the Cu0.5Ga0.5 and Cu0.8Ga0.2 targets were deposited at the rates of 42 nm/min. and 45 nm/min., respectively. The film thicknesses were about 300 nm. Selenization was carried out at different annealing temperatures of T(a) = 450 degrees C, 500 degrees C, 550 degrees C, and 600 degrees C for time periods of 15 min., 30 min., and 60 min. We found that high quality CuGaSe2 films of crystal grains (-1 µm in dia.) fabricated with a reaction using elemental Se at temperatures as low as 450 degrees C for 30 min. When T(a) ≤ 350 degrees C, the Se reaction was insufficient to form CuGaSe2. However, the annealing time had little effect on the formation of CuGaSe2 at T(a) ≥ 450 degrees C. For all the samples, the photoluminescence (PL) emission was only from the donor-acceptor interband transition D1A1 for all the composition ratios of the films [Ga]/[Cu] -1.
