Structural phototransformation of WO3 thin films detected by photoacoustic analysis

The photoacoustic technique (PA) was used to detect the phase transformation from amorphous to crystalline state of tungsten oxide (WO3) thin films induced by UV pulsed laser radiation at low energy (<1.5 mJ). The evolution of photoacoustic signal was studied by a correlation analysis, comparing successive signals at fluences ranging from 0 to 20 mJ/cm2. In this interval, it was possible to observe structural changes and the ablation threshold in films due to incident laser fluence effect. Thin films of WO3 were deposited by DC reactive magnetron sputtering over glass substrates at different deposition times. The results obtained by correlation analysis were compared with Raman spectroscopy data.

► The phototransformation of WO3 thin films were studied by photoacoustic technique. ► The phase transition in WO3 thin films was induced by laser irradiation fluence. ► The onset and end of the phototransformation in the thin films was identified. ► The ablation threshold for each sample was identified.