Publication details

Unravelling local environments in mixed TiO2-SiO2 thin films by XPS and ab initio calculations

Authors

ONDRAČKA Pavel NEČAS David CARETTE Michele ELISABETH Stephane HOLEC David GRANIER Agnes GOULLET Antoine ZAJÍČKOVÁ Lenka RICHARD-PLOUET Mireille

Year of publication 2020
Type Article in Periodical
Magazine / Source Applied Surface Science
MU Faculty or unit

Faculty of Science

Citation
Web https://doi.org/10.1016/j.apsusc.2019.145056
Doi http://dx.doi.org/10.1016/j.apsusc.2019.145056
Keywords TixSi1-xO2; X-ray photoelectron spectroscopy (XPS); Phase separation; Density functional theory (DFT)
Description Mixed TixSi1-xO2 oxide can exhibit a partial phase separation of the TiO2 and SiO2 phases at the atomic level. The quantification of TiO2-SiO2 mixing in the amorphous material is complicated and was so far done mostly by infrared spectroscopy. We developed a new approach to the fitting of X-ray photoelectron spectroscopy data for the quantification of partial phase separation in amorphous TixSi1-xO2 thin films deposited by plasma enhanced chemical vapour deposition. Several fitting constraints reducing the total number of degrees of freedom in the fits and thus the fit uncertainty were obtained by using core electron binding energies predicted by density functional theory calculations on TixSi1-xO2 amorphous supercells. Consequently, a decomposition of the O is peak into TiO2, SiO2 and mixed components was possible. The component areas ratios were compared with the ratios predicted by older theoretical models based on the atomic environment statistics and we also developed several new models corresponding to more realistic atomic structure and partial mixing. Based on the comparison we conclude that the studied films are mostly disordered, with only a moderate phase separation.
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