Control over crystallite orientation in thin-films is important for improving charge carrier transport in heterojunction devices such as solar cells. We have synthesized anatase TiO2 films with strong &lt;001&gt; texture on gold substrate that may improve the efficiency since charge transport and electron injection were found to have reduced barriers along the [001] direction. SEM images reveal that the grains are small near the substrate and expand into a wedge shape at the exterior surface of the film. To elucidate film nucleation and growth, the films were polished such that one end of the film had a thickness of 10 nm and the other end a distance 12 mm away had a thickness of ~400 nm. Electron micrographs were acquired at select thicknesses between 10 – 400 nm and the film was characterized at each point by synchrotron X-ray diffraction employing an area detector. Pole figures of the (004) anatase reflection were constructed from rocking curves and grazing incidence patterns after correction for background, polarization, and absorption effects. The TiO2 films exhibit &lt;001&gt; texture that is strong at the surface of the film and weaker close to the substrate. However, analysis of the {101} reflection shows that three distinct orientations exist (χ = ±68o, ±38o, ±18o) at a film thickness of 10 nm. This unexpected finding suggests that nucleation is not random and may be influenced by the substrate. As the film grows, the (101) orientation (χ = ±68o) consistent with &lt;001&gt; texture dominates. An understanding of crystal nucleation and growth under hydrothermal conditions will allow control over the film texture, which will improve charge transport properties. To observe nucleation and growth steps in-situ, a hydrothermal cell was designed to measure WAXS and SAXS simultaneously. The results of our ex-situ study and strategy for in-situ measurements will be described.

Ex-situ profiling of TiO2 thin film growth: An XRD study using synchrotron radiation

253rd National Meeting (2017)

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