An electron paramagnetic resonance investigation of paramagnetic defects in diamond films grown by chemical vapour deposition

Abstract

Defects in free-standing diamond films grown by microwave-plasma-assisted chemical vapour deposition have been studied by electron paramagnetic resonance (EPR). The EPR spectra observed for the as-grown material each consisted of two distinguishable Lorentzian lines at g = 2.0028(2), along with weak satellites centred on g = 2.0028 and separated from each other by 1.15 - 1.35 mT. Comparison of the local concentration (up to 500 ppm) determined by lineshape analysis and the bulk concentration (0.3 - 8 ppm) determined from the total EPR absorption revealed that the defects were inhomogeneously distributed in the diamond film. Multi-frequency EPR measurements showed that the satellite separation depended on the microwave frequency. It is proposed that the satellite lines originate from a pair of coupled electron spins which form a biradical centre. This appears to be the only model which is consistent with the observed microwave frequency dependence of the satellite separation.