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 [11¯00]ZnO//[112¯0]Cr2O3//[11¯0]Cr//[112¯0]Al2O3 and [112¯0]ZnO//[11¯00]Cr2O3//[0 0 1]Cr//[11¯00]Al2O3. 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.