Silicon and carbon vacancies in silicon carbide studied by coincidence Doppler broadening spectroscopy

Abstract

Deconvoluted Coincidence Doppler Broadening Spectroscopy (CDBS) measurements have been made on 300 keV and 1.7 MeV electron irradiated SiC. The lower energy irradiation produces only carbon vacancies while the higher energy produces both carbon and silicon vacancies. This distinction is easily seen in the high (20-35 mrad) momentum range where a clear atomic signal of Si is seen for the carbon vacancy. In addition to the higher momentum region the higher resolution of the deconvoluted CDBS spectra show structural information relating to the crystal lattice. The autocorrelation function obtained for positrons trapped at carbon vacancies is found to show a stronger lattice signal indicative of a more extended positron wave function and a less strongly bound state. Conversely that positron trapped at the silicon vacancy shows a more damped autocorrelation function characteristic of a more spatially confined positron state.