Effects of temperature, pressure and pure copper added to source material on the CuGaTe2 deposition using close spaced vapor transport technique

The quality of CuGaTe2 (CGT) thin films elaborated by close spaced vapor transport technique has been studied as a function of the source temperature (T-S), iodine pressure (P-I2) and the amount (X-Cu) of pure copper added to the stoichiometric starting material. A thermodynamic model was developed for the Cu-Ga-Te-I system to describe the CGT deposition. The model predicts the solid phase composition with possible impurities for the operating conditions previously mentioned. The conditions of stoichiometric and near-stoichiometric deposition were determined. The value of T-S must range from 450 to 550 degrees C for P-I2 varying between 0.2 and 7 kPa. Adding an amount up to 10% of pure copper to the starting material improves the quality of the deposit layers and lowers the operating interval temperature to 325-550 degrees C. These optimal conditions were tested experimentally at 480 degrees C and 500 degrees C. The X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy have proved that the addition of pure copper to the stoichiometric source material can be considered as a supplementary operating parameter to improve the quality of CGT thin films. (C) 2013 Elsevier B.V. All rights reserved.