Universal synthesis method for mixed phase TiO<inf>2</inf>(B)/anatase TiO<inf>2</inf> thin films on substrates via a modified low pressure chemical vapour deposition (LPCVD) route

• Main Authors: Chimupala Y., Junploy P., Hardcastle T., Westwood A., Scott A., Johnson B., Brydson R.
• Format: Journal
• Published: 2017
• Online Access: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84967076059&origin=inward; http://cmuir.cmu.ac.th/jspui/handle/6653943832/41939
• Institution: Chiang Mai University

© The Royal Society of Chemistry 2016. A universal method for the synthesis of mixed phase TiO 2 bronze (B)/anatase titania thin films by Low Pressure Chemical Vapour Deposition (LPCVD) onto any substrate is presented. General LPCVD conditions were titanium isopropoxide (TTIP) and N 2 gas as the precursor and carrier gas respectively, 600 °C nominal reaction temperature, and 15 min reaction time; a range of different substrates were investigated including: a silicon wafer, fused quartz, highly ordered pyrolytic graphite (HOPG) and pressed graphite flake (grafoil). X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy were used to characterise the thin films which exhibited a columnar morphology together with smaller equi-axed particles. Pre-treatment of substrates by spraying with a Na-containing solution was found to encourage the crystallization of TiO 2 (B) during the LPCVD process. Increasing the concentration of Na in the pre-treatment process resulted in a higher proportion of TiO 2 (B) in the thin films up to an optimum condition of 0.75% w/v of Na. Na diffusion from the substrate surface into the adjacent TiO 2 is the proposed mechanism for promoting TiO 2 (B) formation as opposed to the anatase phase with Density Functional Theory (DFT) modelling suggesting the presence of Na stabilises the TiO 2 (B) phase. Dye degradation tests indicate an increased photocatalytic activity for mixed phase anatase/TiO 2 (B) thin films.