Role of the oxygen partial pressure on the properties of undoped tin oxide films deposited at low temperature

The aim of this work is to determine the influence of the oxygen partial pressure on the the optical, electrical and structural properties of transparent conductive undoped tin oxide (SnO) thin films. These films were deposited by radio frequency plasma enhanced reactive thermal evaporation (rff-PERTE) of tin in the presence of oxygen at low substrate temperatures (140 degrees C). Electrical properties obtained in such thin films show dependence with the oxygen partial pressure. When pressure ranges from 1.5x10(-2) to 6.0x10(-2) Pa, resistivity varies between 3.3x10(-1) Omega cm and 2.6x10(-1) Omega cm, respectively. The lowest resistivity value obtained was 2.0x10(-2) Omega cm for films deposited at an oxygen partial pressure of about 3.0x10(-2) Pa. All samples present a reasonably good visible transmittance value between 75-85%. Topography of the samples obtained by AFM show a relative uniform and flat surface with mean square roughness (RMS) of the order of 1.1 nm. RBS measurements show that the highest conductivity is obtained for SnOx films with an O/Sn ratio of about 2.51. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.