Characterisation Studies of the Structure and Properties of As-Deposited and Annealed Pulsed Magnetron Sputtered Titania Coatings

• Published in: Coatings (Basel) 2013-09, Vol.3 (3), p.166-176
• Main Authors: Kulczyk-Malecka, Justyna, Kelly, Peter, West, Glen, Clarke, Gregory, Ridealgh, John
• Format: Article
• Language: English
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings3030166

Titanium dioxide thin films are durable, chemically stable, have a high refractive index and good electro/photochemical proprieties. Consequently, they are widely used as anti-reflective layers in optical devices and large area glazing products, dielectric layers in microelectronic devices and photo catalytic layers in self-cleaning surfaces. Titania coatings may have amorphous or crystalline structures, where three crystalline phases of TiO2 can be obtained: anatase, rutile and brookite, although the latter is rarely found. It is known, however, that the structure of TiO2 coatings is sensitive to deposition conditions and can also be modified by post-deposition heat treatments. In this study, titania coatings have been deposited onto soda-lime glass substrates by reactive sputtering from a metallic target. The magnetron was driven in mid-frequency pulsed DC mode. The as-deposited coatings were analysed by micro Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Selected coatings were annealed at temperatures in the range 200–700 °C and re-analysed. Whilst there was weak evidence of a nanocrystallinity in the as-deposited films, it was observed that these largely amorphous low temperature structures converted into strongly crystalline structures at annealing temperatures above 400 °C.