Electron microscopy and Rutherford backscattering study of nucleation and growth in nanosized W–Ti–O thin films

Structural characterization of nanosized W–Ti–O rf magnetron-sputtered films was carried out by means of electron microscopy techniques and Rutherford backscattering spectroscopy. The evolution of the W–Ti–O films turned out to be quite complex as several nanophases were determined. Depending on annealing temperature and W/Ti abundance, stable nanophases of WO3, TiO, and TiO2 have been reliably achieved. The investigation highlighted the reason why the films remained nanostructured in spite of a relatively high annealing temperature. In fact, formation of a dispersed TiO nanophase in the W–Ti–O layers was recognized to inhibit grain growth and promote secondary recrystallization. This resulted in exaggerated growth of WO3 crystallites over the nanostructured layers.