Intrinsic and extrinsic doping contributions in SnO2 and SnO2:Sb thin films prepared by reactive sputtering

Abstract

SnO2 thin films are considered cheap transparent electrodes, interesting for scalable electronic applications, with intrinsic n-type conductivity related to donor defects like tin interstitials and oxygen vacancies. Besides, SnO2 allows n-type extrinsic doping by pentavalent cations such as Ta or Sb. In the present work, SnO2 and SnO2:Sb films were deposited on unheated soda lime glass substrates by reactive DC sputtering from Sn and Sn:Sb(5%) targets. Their structural, optical and electrical properties have been analyzed comparatively for the layers prepared at different oxygen partial pressures in the sputtering atmosphere, as-grown and after heating in air at several temperatures. Sb doping is proven effective to improve the electrical conductivity of sputtered tin dioxide samples. The contribution of oxygen vacancies is found dependent on the reactive deposition environment, in both pure and Sb-doped films, but subsequent heating can change the proportion and nature of the donor defects. For operation at temperatures above 400 ºC, SnO2:Sb shows the best electrical performance and good thermal behavior is also achieved with pure SnO2 layers by adjusting the oxygen content in the sputtering atmosphere.