Etching damage and its recovery by soft X-ray irradiation observed in soft X-ray absorption spectra of TiO2 thin film

Damage characteristics of TiO2 thin films etched by N2 plasma were analyzed using soft X-ray absorption spectroscopy. Changes in the spectra at the Ti-L2,3 near-edge X-ray absorption fine structure (NEXAFS) resulting from etching damage were observed more in the bulk region rather than in the sample surface. The damaged spectra were recovered to the spectra of the as-grown sample by soft X-ray irradiation for 10 min. Moreover, the once-recovered spectrum of the irradiated sample was returned to the disordered shape by storage in dark place for 10 days. These results could have been caused by electron-related structural relaxation in appearance.