Aerosol-assisted fabrication of tin-doped indium oxide ceramic thin films from nanoparticle suspensions

Abstract

Sn-doped In₂O₃ (ITO) thin films were fabricated on float glass substrates from a nanoparticle suspension using a new and inexpensive aerosol-assisted chemical transport (AACT) process. The influence of the solvent type, loading level and film deposition time on the structural, electrical and optical properties of the deposited thin films was investigated. In addition, the effect of the post-deposition heat-treatment of ITO films on the film resistivity and transparency was investigated using microwave radiation and compared with more conventional radiant heat-treated films. The SEM images of the films prepared using a 30 min deposition time with 0.20% (wt/vol%) methanolic ITO suspension provided better surface coverage compared to the other deposition times investigated. The optimised ITO films were heat-treated after deposition by either conventional radiant or microwave assisted heating methods in order to improve the inter-particle connections and film adherence. The films heat-treated after deposition by microwave annealing exhibited an average transmittance of >85% in the visible region with a resistivity of 12 Ω cm and a carrier concentration of −3.7 × 10¹⁶ cm³, which were superior to films that were heat-treated using more conventional thermal processing (despite the shorter processing time for the microwave process). The resistivity of ITO films was further decreased to 6.0 × 10⁻² Ω cm with an increased carrier concentration of −8.0 × 10¹⁸ cm³ when ethyl cellulose was added to the ITO suspension prior to the AACT deposition. The enhanced conductivity of this film is due to the improved particle–particle and particle–substrate connections as observed by SEM imaging.