The high quality ZnO growth on c-Al 2O 3 substrate with Cr 2O 3 buffer layer using plasma-assisted molecular beam epitaxy

Abstract

High quality epitaxial ZnO films were grown on c-Al 2O 3 substrates with Cr 2O 3 buffer layer by plasma-assisted molecular beam epitaxy (P-MBE). The hexagonal crystalline Cr 2O 3 layer was formed by oxidation of the Cr-metal layer deposited on the c-Al 2O 3 substrate using oxygen plasma. The epitaxial relationship was determined to be [ 1 1 ¯ 0 0 ] ZnO// [ 1 1 2 ¯ 0 ] Cr 2O 3// [ 1 1 ¯ 0 ] Cr// [ 1 1 2 ¯ 0 ] Al 2O 3 and [ 1 1 2 ¯ 0 ] ZnO// [ 1 1 ¯ 0 0 ] Cr 2O 3//[0 0 1]Cr// [ 1 1 ¯ 0 0 ] Al 2O 3. The Cr 2O 3 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 Cr 2O 3 buffer.