ELECTRONIC STRUCTURE OF ISOLATED SINGLE VACANCY CENTRES IN SILICON CARBIDE

The lowest electronic levels of the various charged states of the isolated carbon and silicon single vacancies in silicon carbide have been calculated using the defect molecule approach with lattice distortion

LATTICE DISTORTION NEAR VACANCIES IN DIAMOND AND SILICON .1.

A dynamical relaxation procedure, coupled with a valence force potential, has been used to calculate the distortion around point defects in a diamond-type crystal. The method has been applied to the vacancy in diamond and silicon. The response of the lattice to symmetrized forces on the nearest neighbours to the vacancy was calculated. The results can be used in estimates of point defect properties which depend on lattice distortion, including the jahn-teller effect, and formation energies. The ratios of the atomic displacements under uniform external stresses for the perfect lattice and for the lattice with a vacancy are also determined

The structure and motion of the self-interstitial in diamond

We have made self-consistent semi-empirical molecular orbital calculations for various possible self-interstitial geometries in diamond, both with and without lattice distortion. Total energies are obtained, not merely the sum of one-electron eigenvalues. The results show that the (100) split interstitial has the lowest formation energy, not the cubic, hexagonal or bond-centred forms favour previously. The nature of the interstitial does not support the local heating model of enhanced diffusion in the presence of recombination or ionisation. A Bourgoin-Corbett mechanism involving negative hexagonal and neutral split interstitials is possible, but the apparent stability of the negative hexagonal interstitial may be an artefact of the calculation. We suggest a local excitation model is appropriate in fourfold-coordinated semiconductors

Education research in Australia: where is it conducted?

Research assessment exercises aim to identify research quantity and quality and provide insights into research capacity building strategies for the future. Yet with limited knowledge of the ecology of Australian educational research, there is little chance of understanding what research audits might contribute towards a capacity building agenda for such a complex field. This paper draws on secondary data analysis of research outputs submitted by 13 Australian higher education institutions to the Excellence in Research for Australia (ERA) 2010 and 2012 national research assessment exercises, to show where Australian educational research is conducted. Findings offer a profile of education researchers by location in academic organisational units within universities. By analyzing data not accessible through reported ERA data we were also able to present information about appointment profiles, specifically levels and type of appointment within universities, as well as data on institutional and geographic region, and patterns associated with type of outputs (books, book chapters, journal articles, conference papers and other outputs) and field of research. Analysis of the data reveals definitive shifts in the nature of the published outputs and in employment profiles of researchers and their location across university and regional groupings. Research audits are administrative processes that reshape institutional and disciplinary governance structures, policies, individual outputs, work practices and careers, but they are not the sum total of the field per se

Calibrating and testing tissue equivalent proportional counters with 37Ar

A method for testing and calibrating tissue equivalent proportional counters with37Ar is described.37Ar is produced by exposure of argon in its normal isotope composition to thermal neutrons. It is shown that - up to volume ratios of 0.01 of argon to the tissue equivalent gas - there is no appreciable effect of the argon admixture on the function of the proportional counter. Conventional calibration methods with characteristic x-rays or with -particles require modifications of the detectors, and they test only small sub-volumes in the counters. In contrast, argon permits calibrations and tests of the resolution that are representative for the entire counter volume and that do not require changes in detector construction. The method is equally applicable to multi-element proportional counters; it is here exemplified by its application to a long cylindrical counter of simplified design that is part of such a multi-element configuration