Controlled electrical conductivity in SnO2 thin films by oxygen or hydrocarbon assisted atomic layer epitaxy

The conventional atomic layer epitaxy process for pure SnO2 thin films uses SnCl4 and H2O as precursors and Np as the carrier gas. By applying gas-pha se additives (n-hexane, ozone) or using oxygen as a carrier gas, a reduced electrical conductivity of the solid was obtained. This phenomenon is assoc iated with the modifications in the grain structure and/or in the point def ect concentration. To verify this, structural studies by X-ray diffraction, atomic force microscopy, Auger electron spectroscopy, and secondary ion ma ss spectroscopy were performed. The results suggest that the variations in electrical resistivity (0.1-89 Omega cm) are predominantly due to variation s in the electronic carrier concentration, i.e., oxygen vacancy and/or chlo rine-impurity concentrations, which were induced by gas-phase additives. Th e most promising additive was hexane, as it resulted in SnO2 firms of the l owest conductivity as well as the highest crystallinity and stoichiometry. The strength of this effect was, however, dependent on the position of hexa ne pulse in the pulsing sequence. (C) 1999 The Electrochemical Society. S00 13-4651(98)04-017-8. All rights reserved.