Growth of ZnO by molecular beam epitaxy using NO2 as oxygen source

Nitrogen dioxide was applied for molecular beam epitaxy of ZnO on (0001) sapphire substrates. Equipped with liquid nitrogen cryoshrouds, the pressure inside the chamber was kept below 1 x 10(-7) Torr during growth. The samples were characterized by reflection high energy electron diffraction, X-ray diffraction, photoluminesence and scanning electron microscopy. The ZnO crystals clearly showed excitonic optical properties up to room temperature. Effects of low-temperature buffer layers for better surface morphology and reproducibility were also investigated.