Growth of ZnO on Si substrate by plasma-assisted molecular beam epitaxy

Epitaxial ZnO films have been grown on Si(111) substrates by molecular beam epitaxy using oxygen plasma. An initial Zn layer deposition followed by its oxidation produces a superior template for the subsequent ZnO growth and a low-temperature ZnO buffer layer improves the structural and optical properties of ZnO films. As a result, we succeeded in growing high-quality ZnO films directly on Si substrates. We observed cracks composed of straight lines along the principal axes of the Si(111) surface. These cracks are probably caused by the difference in thermal expansion coefficient between ZnO and Si. X-ray diffraction measurements reveal that ZnO films do not include a rotational domain and the full width at half maximum of the diffraction peak of ZnO(0002) is 0.23 deg. The linewidth of the neutral-donor-bound exciton emission at 3.365 eV is as small as 6 meV at 10 K.