Room-temperature stimulated emission from ZnO thin films grown by radio-frequency magnetron sputtering

ZnO thin films have been deposited by RF-magnetron sputtering on SiO2 substrates. A, B excitons from the absorption spectra at room temperature and A, B and C excitons from the reflectance spectra at the temperature below 166.7 K have been clearly observed. These results indicate that ZnO thin films have a good wurtzite crystal structure. The stimulated emission has been observed at room temperature under various excitation intensities. In the edge emission geometry we determine the gain magnitude with the variable stripe length method. The optical gain is shown as a result of the electron-hole plasma process, and exhibits the highest gain reaching value 270 cm-1 at an excitation density of 1122 kW/cm2