Silicon electron-nuclear double-resonance study of the NL10 heat-treatment center

²⁹Si electron-nuclear double-resonance (ENDOR) measurements were performed for the Si-NL10 center. The results were compared with the ²⁹Si ENDOR measurements of the Si-NL8 spectrum and were found to be similar with the defect electron being even more delocalized in the case of the Si-NL10 center. The wave function is found to be approximately [100] axially symmetric with no symmetry-forbidden mirror planes. This indicates the A₁ ground state for the Si-NL10 defect in analogy with the ground state for Si-NL8. Field-stepped ENDOR measurements show that the ²⁹Si hyperfine interactions originate from a series of different but otherwise very similar centers, each of which generates its own EPR spectrum, which, however, remains unresolved in the EPR experiment. This confirms the results obtained previously from ²⁷Al and ¹⁷O ENDOR studies for the Si-NL10 center. The close analogy of the silicon ENDOR data for the Si-NL8 and Si-NL10 centers is indicative of a very similar structure of both centers.