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Mg(sub x)Zn(sub 1-x)O layers with different crystal structures due to different Mg contents are grown on a MgO/Al2O3(0001) template. The results images demonstrate that the epitaxial orientation of Mg(sub x)Zn(sub 1-x)O films with less than or equal to 0.65 on the MgO buffer layer initially is along [111] cubic direction and then changed to [0001] wurtzite direction.

The authors report on the growth mechanism of ZnO homoepitaxy at the low-temperature range of 500 °C, which is unavailable to obtain high-quality ZnO films in heteroepitaxy. One typical set of ZnO films were grown on (0001) ZnO substrates by molecular-beam epitaxy: a standard structure without buffer and two buffered structures with high-temperature (HT) homobuffer and low-temperature (LT) homobuffer. As a result, the LT homobuffered structure had the outstanding material properties: the surface roughness is 0.9 nm, the full width at half maximum of x-ray rocking curve is 13 arcsec, and the emission linewidth of donor-bound excitons is 2.4 meV. In terms of the theoretical interpretation of the experimentally obtained electron mobilities, it was found that the LT homobuffered structure suffers less from the dislocation scattering and the ionized-impurity scattering compared to the HT homobuffered structure. It is proposed that, in the ZnO low-temperature homoepitaxy, the LT homobuffer plays a key role in inducing the complete termination of dislocations in the homointerface and suppressing the outdiffusion of contaminants and point defects on the ZnO surface, which results in the formation of smooth wetting layer on the homointerface. [ABSTRACT FROM AUTHOR]

We report on the crystallinity, N incorporation efficiency, optical properties, and electrical properties of N and Te codoped ZnO films grown by plasma-assisted molecular-beam epitaxy. Te improves the surface morphology and roughness of ZnO films in terms of both streak reflection high energy electron diffraction pattern and atomic force microscopy observations. Also, N and Te codoping is helpful to improve the crystallinity and N incorporation efficiency simultaneously. We found that; (a) narrower x-ray linewidth and higher N concentration were obtained by codoping. (b) Nitrogen related emission lines including donor-acceptor pair and acceptor-bound exciton dominantly emerged in photoluminescence spectra. (c) Codoping enhanced the carrier compensation of native donors in ZnO films and suppressed the dislocation scattering. As a consequence, we concluded that N and Te codoping is very effective for the growth of reliable p-type ZnO films which fulfill the controversial requirements; high N concentration and high crystallinity, simultaneously. [ABSTRACT FROM AUTHOR]

We report on the anisotropic structural properties of periodically polarity-inverted (PPI) ZnO structures grown on patterned templates. The etching and growth rates along [formula] direction of ZnO structures are higher than those of [formula] direction of ZnO films. From the strain evaluation by Raman spectroscopy, compressive strains are observed in all PPI ZnO samples with different stripe pattern size and the smaller pattern size is more effective to residual stress relaxation. The detailed structures at transition region show relationship with the anisotropic crystal quality. [ABSTRACT FROM AUTHOR]

We report on the structure study of MgxZn1-xO films and, in particular, we will focus on MgxZn1-xO layers with x=0.28 and 0.41 MgxZn1-xO layers with different crystal structures of cubic and wurtzite that have been grown by plasma-assisted molecular-beam epitaxy on MgO/c-sapphire with Mg/Zn flux ratio control. The MgxZn1-xO films have been characterized by high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction. The dependence of the cation-anion bond length to Mg content has been studied. A virtual crystal model of MgZnO has been applied to interpret the bond-length variation. HRTEM results indicate that the initial stage of the MgZnO growth on a MgO buffer layer starts with a cubic structure even in the case of a wurtzite structure at the end of growth. [ABSTRACT FROM AUTHOR]

A photoanode prepared from flux-synthesized Al-doped SrTiO3 by the particle transfer method with a Ta contact layer exhibited a high IPCE of 69% at 320 nm. The photocatalytic activity of SrTiO3 particles was very sensitive to the synthesis method used to make the SrTiO3 particles, while its photoelectrochemical performance was not. [ABSTRACT FROM AUTHOR]