Microstructure and physical properties of nanofaceted antimony doped tin oxide thin films deposited by chemical vapor deposition on different substrates

Antimony doped tin oxide SnO2,: Sb thin films have been fabricated by atmospheric pressure chemical vapour deposition at substrate temperature varying between 350 degrees C and 420 degrees C in a horizontal reactor, from a mixture of hydrated SnCl2, SbCl3 and O-2 gas. The films were grown on glass substrates and onto polished and porous n-type silicon. Doped films fabricated with various Sb (Sb/Sn %) contents ranging from undoped 0% to 4% were characterised employing different optical characterisation techniques, like X-ray diffraction, transmittance and reflectance in the wavelength range of 300 to 2500 nm and ellipsometry. The films exhibit the usual cassiterite diffraction pattern with high crystalline structure. Examination of the surface by scanning electron microscopy (SEM) showed that the films are textured made up of many pyramidal crystallites with nanofaceted surfaces, indicating highly stabilised material. The presence of inverted pyramids indicates that the crystallites grown by coalescence. The surface morphology was found to be independent on the kind of the substrate. From X-Ray spectra and SEM observations we get the texture the lattice constant and the grain size. The optical results provide information on film thickness, optical parameters and transmittance upon antimony concentration. The microstructure of the films, the grain growth topics (nucleation, coalescence) depend strongly on deposition conditions and doping concentration. The observed variations of both the resistivity p and transmittance T are correlated to antimony atoms concentration which induced variation in the microstructure and in the size of SnO2 nanograins (typically 20-40 mn). In this work, we have determined the feasibility of incorporating the correct amount of Sb atoms in tin oxide film by means of resistivity and transmission. SEM observations showed that the substrate do not affect the morphology. (C) 2007 Elsevier B.V. All rights reserved.