S. A. Hatfield

Valence band offset of the ZnO/AlN heterojunction determined by x-ray photoemission spectroscopy

The valence band offset of ZnO/AlN heterojunctions is determined by high resolution x-ray photoemission spectroscopy. The valence band of ZnO is found to be 0.43±0.17 eV below that of AlN. Together with the resulting conduction band offset of 3.29±0.20 eV, this indicates that a type-II (staggered) band line up exists at the ZnO/AlN heterojunction. Using the III-nitride band offsets and the transitivity rule, the valence band offsets for ZnO/GaN and ZnO/InN heterojunctions are derived as 1.37 and 1.95 eV, respectively, significantly higher than the previously determined values.

X-ray photoemission spectroscopy determination of the InN/yttria stabilized cubic-zirconia valence band offset

The valence band offset of wurtzite InN(0001)/yttria stabilized cubic-zirconia (YSZ)(111) heterojunctions is determined by x-ray photoemission spectroscopy to be 1.19±0.17eV giving a conduction band offset of 3.06±0.20eV. Consequently, a type-I heterojunction forms between InN and YSZ in the straddling arrangement. The low lattice mismatch and high band offsets suggest potential for use of YSZ as a gate dielectric in high-frequency InN-based electronic devices.

Synchrotron X-ray diffraction in air and vacuum: Strain and structure at the nano-scale

The simultaneous use of symmetric and grazing incidence X-ray diffraction in the characterisation of a pnictide material is demonstrated using MnSb epi-layers grown on compound semiconductor substrates. This combination of diffraction geometries enables a comprehensive determination of the lattice parameters and complex structural behaviour of MnSb. For example, in the ultra-thin limit (<;5 nm) of layers grown on GaAs an evolution from coherently strained to relaxed islands is observed with increasing thickness. However, a mixture of both strained and relaxed islands is seen beyond the calculated critical thickness. As film thickness increases, a cubic polymorph is observed and the relative content of this polymorph was probed using reciprocal space maps. Finally, recent surface X-ray diffraction work performed under ambient conditions is compared with similar data obtained at ultra-high vacuum conditions. The information found using these complementary diffraction geometries can readily be applied to a range of compound semiconductors.