Abstract

TiO2 films are grown on LaAlO3 (001), Si (100) and SiO2 substrates by reactive radio frequency sputtering. X-ray diffraction (XRD) pole figures revealed important characteristics about the texture and phase distribution on those films. Combined with spectroscopic ellipsometry, the pole figures allowed the analysis of the growth characteristics over the whole volume of the layers. Details in the microstructure of the films were probed using transmission electron spectroscopy. Anatase is the dominating phase in the films grown on all substrates. On TiO2/LaAlO3 fims, the mosaicity is very low, so that the pole figure closely resembles that of anatase monocrystals. Detailed inspection of XRD pole figures reveals a small amount of rutile in the TiO2/LaAlO3 films. For the growth of TiO2 onto SiO2, rutile and brookite phases are also detected. Transmission electron microscopy and XRD results show the formation of anatase {112} twins in films grown on the different substrates, suggesting that the anatase {112} twin mediates the growth of rutile and brookite phases. Optical results are in agreement with the XRD observations: the optical properties of TiO2/LaAlO3 films are similar to the ordinary values of bulk anatase crystals, indicating the orientation of the film in the [001] direction, whereas results for TiO2/SiO2 are compatible with lower crystalline ordering.

Highlights

  • Titanium dioxide (TiO2) is a wide band gap semiconductor that has been intensively studied since the observation of water photolysis on its surface in 1972.1 Nowadays, TiO2 is the most widely used oxide for photocatalysis of organic pollutants.[2,3,4] In past years, new applications in the elds of biocompatibility,[5] self-cleaning processes,[6] photovoltaics,[7] lithium ion batteries[8] and high-k gate dielectrics[9] have reinforced the needs for research on TiO2 lm deposition methods

  • Detailed inspection of X-ray diffraction (XRD) pole figures reveals a small amount of rutile in the TiO2/ LaAlO3 films

  • Transmission electron microscopy and XRD results show the formation of anatase {112} twins in films grown on the different substrates, suggesting that the anatase {112} twin mediates the growth of rutile and brookite phases

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Summary

Introduction

Titanium dioxide (TiO2) is a wide band gap semiconductor that has been intensively studied since the observation of water photolysis on its surface in 1972.1 Nowadays, TiO2 is the most widely used oxide for photocatalysis of organic pollutants.[2,3,4] In past years, new applications in the elds of biocompatibility,[5] self-cleaning processes,[6] photovoltaics,[7] lithium ion batteries[8] and high-k gate dielectrics[9] have reinforced the needs for research on TiO2 lm deposition methods. Relevant results concerning the anatase growth onto LAO by reactive sputtering were reported by Wang et al.[34] They combined advanced transmission electron microscopy with high-precision rst-principles calculation to relate the crystalline structure of TiO2/LAO interface to its electronic properties.

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