A comparative study of ion-assisted e-beam evaporated titania thin films

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Author list: Eiamchai P., Chindaudom P., Pokaipisit A., Limsuwan P.

Publisher: World Scientific Publishing

Publication year: 2010

Journal: International Journal of Modern Physics B: Condensed Matter Physics; Statistical Physics; Atomic, Molecular and Optical Physics (0217-9792)

Volume number: 24

Issue number: 18

Start page: 3513

End page: 3528

Number of pages: 16

ISSN: 0217-9792

eISSN: 1793-6578

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956093031&doi=10.1142%2fS0217979210055652&partnerID=40&md5=f7d18735526e92f63500489fd1825ddc

Languages: English-Great Britain (EN-GB)

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Abstract

Titanium dioxide has been in close examination for application development due to its high index of refraction and transparency across the visible range. One of the most active researches is hydrophilicity and photocatalysis in TiO2 films. In this study, a close investigation to TiO2 films' microstructural transformation was examined. A number of thin film samples were prepared by ion-assisted electron-beam evaporation at 200-nm nominal thickness, 2.0 ล/s deposition rate and 250ฐC deposition temperature. The varying parameter was the oxygen flow rate at 2, 4, 6 and 8 sccm. The films were eventually annealed for three hours in air atmosphere. The crystalline structures of as-deposited (ASD) and annealed films were deduced by variable-angle spectroscopic ellipsometry (VASE), and supported by X-ray diffractometry (XRD) and atomic force microscopy (AFM). Film characterization based on VASE is desirable in order to understand physical and optical characteristics of the films. Transmittance spectra were derived from UV/Vis spectrophotometer. It was found that all as-deposited films were all amorphous with low luminous transmittance. Higher oxygen flow rate during the deposition, however, resulted in sub-oxide TiO2 film. With this film, annealing at 300 and 500ฐC were presumed as transition temperatures for amorphous-to-anatase and anatase-to-rutile phases, respectively. The luminous transmittance also increased and was found to be the highest at 75.75% at 400ฐC annealing. The optical energy band gap for this film also increased up to 3.26 eV at 600ฐC annealing. ฉ 2010 World Scientific Publishing Company.

Keywords

Ellipsometry