Spray pyrolysis deposition of indium sulphide thin films

In2S3 thin films were grown by the chemical spray pyrolysis (CSP) method using the pneumatic spray set-up and compressed air as a carrier gas. Aqueous solutions containing InCl3 and SC(NH2)(2) at a molar ratio of In/S = 1/3 and 1/6 were deposited onto preheated glass sheets at substrate temperatures T-s = 205-410 degrees C. The obtained films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM,) optical transmission spectra, X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). According to XRD, thin films deposited at T-s = 205-365 degrees C were composed of the (0 0 12) orientated tetragonal beta-In2S3 phase independent of the In/S ratio in the spray solution. Depositions performed at T-s = 410 degrees C led to the formation of the In2O3 phase, preferably when the 1/3 solution was sprayed. Post-deposition annealing in air indicated that oxidation of the sulphide phase has a minor role in the formation of In2O3 at temperatures up to 450 degrees C. In2S3 films grown at T-s below 365 degrees C exhibited transparency over 70% in the visible spectral region and E-g of 2.90-2.96 eV for direct and 2.15-2.30 eV for indirect transitions, respectively. Film thickness and chlorine content decreased with increasing deposition temperatures. The XPS study revealed that the In/S ratio in the spray solution had a significant influence on the content of oxygen (Me-O, BE =530.0 eV) in the In2S3 films deposited in the temperature range of 205-365 degrees C. Both XPS and EDS studies confirmed that oxygen content in the films deposited using the solution with the In/S ratio of 1/6 was substantially lower than in the films deposited with the In/S ratio of 1/3. (C) 2010 Elsevier B.V. All rights reserved.