The high quality ZnO growth on c-Al2O3 substrate with Cr2O3 buffer layer using plasma-assisted molecular beam epitaxy

High quality epitaxial ZnO films were grown on c-Al₂O₃ substrates with Cr₂O₃ buffer layer by plasma-assisted molecular beam epitaxy (P-MBE). The hexagonal crystalline Cr₂O₃ layer was formed by oxidation of the Cr-metal layer deposited on the c-Al₂O₃ substrate using oxygen plasma. The epitaxial relationship was determined to be ZnO//Cr₂O₃//Cr//Al₂O₃ and ZnO//Cr₂O₃//[0 0 1]Cr//Al₂O_3. The Cr₂O₃ buffer layer was very effective in improving the surface morphology and crystal quality of the ZnO films. The photoluminescence spectrum showed the strong near band-edge emissions with the weak deep-level emission, which implies high optical quality of the ZnO films grown on the Cr₂O₃ buffer.