Understanding the change in electrical resistance of TiO ₂ thin film irradiated with YVO ₄ third‐harmonic generation pulse laser

Abstract To selectively control the electrical resistance, thin films of TiO ₂ were irradiated with a YVO ₄ third‐harmonic generation pulse laser in various power conditions. It was observed that when the laser power was less than 0.26 W, the electrical resistance of thin films decreased with the increase in laser power, whereas when the laser power was more than 0.26 W, the electrical resistance increased as the laser power increases. The minimum electrical resistance of the irradiated thin film was found to be four orders of magnitude lower than that of the unirradiated thin film. X‐ray absorption fine structure analysis revealed that the valence of Ti ions in the thin films was reduced after laser irradiation, indicating the formation of oxygen vacancies with electron doping. The cross‐sectional observation by a scanning electron microscope revealed that high laser power irradiation caused the thin films to become porous, and the percolation theory explains the origin of the increase in electrical resistance with developing porous structure. We propose a phase diagram to completely explain the relationship between electrical resistance and laser power, which supply a guideline on laser modification in TiO ₂ electrical resistance.