Structural and Optical Properties of Nonpolar (11 ¯ ZnO Films Grown by Plasma-Assisted

Structural and optical properties of ZnO epilayers grown on r-plane sapphire substrates by plasma-assisted molecular-beam epitaxy have been investigated using various tech- niques. A high-purity wurtzite structure and a smooth surface with an a-plane orientation were obtained. The resonant Raman scattering spectra show a typical multiphonon vibration charac- teristic from wurtzite ZnO. A good near band gap luminescence property is revealed in photoluminescence spectra. Index Terms—a-plane ZnO, photoluminescence (PL), Raman, X-ray diffraction (XRD).