Aerosol-assisted fabrication of tin-doped indium oxide ceramic thin films from nanoparticle suspensions
journal contributionposted on 25.05.2016, 13:16 by Nirmal Peiris, Shaghayegh Ghanizadeh, Subhashi Jayathilake, David HuttDavid Hutt, Upul Wijayantha-Kahagala-GamageUpul Wijayantha-Kahagala-Gamage, Paul ConwayPaul Conway, Darren SoutheeDarren Southee, I.P. Parkin, P. Marchand, J.A. Darr, C.J. Carmalt
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 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 x 1016 cm 3 , which was 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 x 10-2 Ω cm with increased carrier concentration of -8.0 x 1018 cm 3 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.
This research was funded by the UK Engineering and Physical Sciences Research Council (EPSRC) under grant number EP/L017709/1. The authors also gratefully acknowledge the support of the industrial collaborators, especially Malvern Instruments Ltd., Sun Chemical Ltd. and NSG, Pilkington. The assistance received from all members of the Energy Research Laboratory in the Department of Chemistry, Loughborough University is also acknowledged. The authors acknowledge use of facilities with the Loughborough Materials Characterisation centre (LMCC) and CREST Loughborough University. We would like to thank Dr. Keith Yendall, Dr. Jagdeep Sagu and Dr. Patrick Isherwood for their assistance given in getting titled SEM images and Hall Effect measurements.