Oxygen polarity and interfacial structure of an Mg0.55Zn0.45O/ Mg0.17Zn0.83O/MgO/sapphire heterostructure were determined by electron energy-loss spectroscopy and aberration-corrected scanning transmission electron microscopy. It was found that O-polarity occurs by an uncommon mechanism in the MgxZn1-xO film with a 0.5 nm-thick compressively strained rocksalt MgO buffer; and that the ∼18% lattice mismatch between Mg0.17Zn0.83O and sapphire is mostly accommodated by misfit dislocations at the Mg0.17Zn 0.83O/MgO interface. Density functional theory calculations indicate that the MgO buffer strongly tends to manifest a rocksalt structure rather than wurtzite. Zn substitution of the topmost Mg atoms in the MgO buffer is likely to induce such O-polarity.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films