Annealing effects on structural and optical properties of ZnMgO films grown by RF magnetron sputtering

Two sets of ZnMgO thin films have been fabricated on Si (111) substrates by RF magnetron sputtering, and were annealed at air atmosphere afterwards. The effects of annealing temperature and time on structural and optical properties were also characterized by X-ray diffraction, scanning electron microscopy and photoluminescence (PL) spectra. For samples fabricated at a lower temperature (200 °C, defined as samples I), the experimental results revealed that only hexagonal phase was observed for the films annealed at the temperature range from 180 to 420 °C, and the best crystal quality for the films was found at 240 °C. For samples synthesized at 220 °C (defined as samples II), the crystal structures exhibited anneal-time dependent. The experimental results revealed coexistence of hexagonal and cubic phase when they were annealed at a set temperature of 220 °C with the different annealing time, and the best one can be observed when the anneal time was 30 min. PL spectra showed blue shift for UV peak with the increase of annealing temperature for samples I, and the UV emission occurred red shift and then blue shift when the anneal time increased from 20 to 30 min for samples II.