Control of electrical resistance and temperature of titanium dioxide film by local heating with CW fiber laser

Titanium dioxide (TiO₂) film has photocatalytic properties and good biocompatibility. To expand the film application, formation of oxygen deficiencies in the film was one of the useful methods. Electrical resistance of the film can be decreased due to oxygen deficiencies formation. The local heating process in vacuum is a useful method to create the oxygen deficiencies in local area of the film. Electrical resistance might be locally decreased by local heating with a CW fiber laser. In our experiment, the films were irradiated with the laser in vacuum. Control of temperature on the film was very important for reducing the electrical resistance. Therefore, temperature monitoring of the laser focusing spot area on the film was performed. Temperature of the laser focusing spot area was increased as the laser intensity was increased. Then, the electrical resistance of the laser focusing spot area was decreased as the laser intensity was increased. Thus, electrical resistance of the laser focusing spot area was decreased as temperature of the laser focusing spot area was increased. These results indicated that electrical resistance of the laser focusing spot area was controlled by changing temperature on the laser focusing spot area.