Surface character of titania changed by excimer laser

The electric conductivity changes markedly when titania is irradiated by a proper-fluence excimer laser, it changes from insulator to semiconductor at room temperature, and its color changes too. Several titania samples before and after irradiation are studied with XRD, XPS and microscopic analyses. It is observed that the changes takes place when proper-fluence excimer laser pulse irradiates the surface of titania and the temperature of the surface rises quickly. A thin layer of the irradiated area melts quickly and soon re solidifies. This leads oxygen in titania to vacate partly, so the stoichiometry of the sample deviates from the normal value. The laser fluence threshold is estimated by the equation of heat transfer and the result agrees approximately with the experiment