Lasing action of high quality ZnO thin film deposited by radio-frequency magnetron sputtering

ZnO thin films are deposited on SiO2 substrates by radio-frequency magnetron sputtering. A and B excitons are observed from the absorption spectra at room temperature. A, B and C excitons are observed from the reflectance spectra at 19 K. These results indicate that the obtained ZnO films have a good wurtzite structure. We obtain the stimulated emission resulting from electron-hole plasma. The lasing spectrum is observed, which consist of a large number of narrow peaks with an around 0.5 nm spacing in between, corresponding to a self-formed cavity length of around 31.5 μm. The self-formation of laser cavity in the ZnO thin film is closed related to its the hexagon structure.