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Zinc oxide, a wide-gap semiconductor, typically exhibits n-type conductivity even when nominally undoped. The nature of the donor is contentious, but hydrogen is a prime candidate. We present ab initio calculations of the migration barrier for H, yielding a barrier of less than approximately 0.5 eV. This indicates isolated hydrogen is mobile at low temperature and that thermally stable H-related donors must logically be trapped at other defects. We argue this is also true for other oxides where H is a shallow donor.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Photoemission spectroscopy demonstrates the formation of a surface gold nitride upon irradiation of a Au͑110͒ surface with 500 eV nitrogen ions at room temperature. After irradiation two N1s peaks are observed at binding energies of 396.7± 0.2 eV and 397.7± 0.2 eV along with a broadening of the Au4d 5/2 line. Changes in valence-band spectra are also observed, including an additional density of states at 1.6 eV binding energy and new states at ϳ3.1 eV. Annealing experiments indicate that the two N1s lines are associated with nitrogen compounds of differing thermal stability, possibly due to the formation of more than one nitride phase. To further investigate the properties of gold nitride we have undertaken ab initio pseudopotential calculations on the most likely nitride stoichiometry, Au 3 N, and identified a novel triclinic crystal structure of a significantly lower energy than the anti-ReO 3 expected from a simple consideration of the periodic table, although the latter structure is also found to be stable. The triclinic structure is determined to be metallic, of importance to possible applications.

Doping of diamond using multi‐component, multi‐species structures has been modelled using density functional methods. We find that few combinations of impurities yield donor levels shallower than phosphorus. Complexes involving impurities from the second or lower rows of the periodic table are unbound, and those involving the soluble element nitrogen can often be arranged in passive or even compensating geometries. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)