Dimensional constraints favour high temperature anatase phase stability in TiO2 nanorods

High temperature stable anatase phase TiO2 nanostructures have the potential to advance the fields such as photocatalysis, solar cells and batteries. However, it is challenging to grow TiO2 nanostructures that can retain the anatase phase at high temperatures. Here, we report slanted TiO2 nanorods grown on Si substrates by glancing angle deposition technique employing electron beam evaporation to showcase the anatase phase stability up to 800 degrees C. FESEM surface morphology shows that the nanorods started deforming above 600 degrees C and collapsed at 800 degrees C. We carried out image processing of the nanorods assembly and quantified the deformation with annealing temperature. The x-ray diffraction and Raman spectroscopy utilized for the phase information showed that the anatase phase is stable even at 800 degrees C. Further, we have studied the effect of deformation on wettability of the nanorods system and found that annealed samples are superhydrophilic. Remarkably, the annealed TiO2 nanorods have transformed to hydrophobic when kept in the dark storage due to the structural contribution to contact angle rather than surface energy. Notably, the hydrophobicity increases with time, which was studied for 25 months. The stable high temperature anatase phase could find application in the solar cells, photocatalysis, smart windows, self-cleaning coatings, etc.

Automated summary

The study demonstrates the successful growth of high temperature stable anatase phase TiO2 nanostructures using the glancing angle deposition technique. The annealed TiO2 nanorods exhibit unique wetting properties, with the structural contribution playing a key role in contact angle and increasing hydrophobicity over time.