Thin Solid Films, Vol.519, No.18, 6115-6119, 2011
Optical, electrical and structural properties of Cu2Te thin films deposited by magnetron sputtering
Thin films of Cu2Te were deposited, at room temperature, on glass substrates by magnetron sputtering from independent Cu and Te sources. This work presents the effect of annealing temperature on the optical, structural, and electrical properties of sputtered Cu2Te films. Annealing above 300 degrees C resulted in stoichiometric and near stoichiometric Cu2Te phases, whereas temperatures above 400 degrees C yielded films with single Cu2Te phase. In contrast, annealing at temperatures of 250 degrees C and below resulted in mixed phases of CuTe, Cu7Te5, Cu1.8Te, and Cu2Te. Analyses of transmittance and reflectance measurements for Cu2Te indicate that photon absorption occurs via indirect band transitions for incident photons with energy above the band gap energy and free carrier absorption below the band gap energy. The determined indirect band gap was 0.90 eV and its associated phonon energy was 0.065 eV. Optical phonon scattering was identified as the mechanism through which the momentum is conserved during absorption by free carriers. Electrical measurements show p-type conductivity and highly degenerate semiconducting behavior with a hole carrier concentration p = 5.18 x 10(21) cm(-3). (C) 2011 Elsevier B.V. All rights reserved.
Keywords:Cu compounds;Sputtering;Solar cells;X-ray diffraction;Optical absorbtion;Electrical conductivity