Effects of excimer laser annealing on electrical properties of ZnO polycrystalline films deposited by sputtering

KrF excimer pulsed laser with wavelength of 248 nm was used to anneal the ZnO polycrystalline films deposited on silica glass substrates by radio frequency reactive sputtering. The laser pulse duration was 20 ns and energy density was 267 mJ/cm². After laser annealing, the resistance of the ZnO film measured by four-probe method decreased sharply. The resistance of samples under UV illumination at 254 nm decreased too. Moreover, the ratio of dark resistance to photoresistance reduced, this was not good for enhancing the sensitivity of the UV detector fabricated by the ZnO film. From the results of Hall Effect measurement, it was found that the carrier concentration of the samples increased and mobility of the samples decreased. The reason may be that melting and recrystallization induced by laser irradiation brought some defects into the films for large energy density.