Electron paramagnetic resonance spectroscopy of lithium donors in monoisotopic silicon

Electron paramagnetic resonance (X-band EPR) spectra are reported for lithium-related donors in monoisotopic silicon. High resolution EPR spectra of lithium donor centers in monoisotopic silicon, enriched by (28)Si isotope (99.99%) with very narrow individual lines are observed. In monoisotopic silicon sample ((28)Si enriched floating zone silicon with low concentration of lithium similar to 10(16) cm(-3)), the trigonal EPR spectrum, with well resolved (7)Li hyperfine structure is recorded in the temperature range 3.5-20 K. This spectrum was attributed to LiO complex. At high concentration of lithium (about 10(18) cm(-3)) in monoisotopic silicon two types of spectra are observed. The trigonal one has the same feature as for low concentration of lithium with g-values: g(parallel to) = 1.9974 and g(perpendicular to) = 1.9989. Another spectrum consists of two lines and has tetragonal symmetry with g(parallel to) = 1.9992 and g(perpendicular to) = 1.9983. This spectrum is more intensive than the trigonal one and has no resolved hyperfine structure probably due to time averaging of the hyperfine interaction caused by hopping motion of electrons. (C) 2009 Elsevier B.V. All rights reserved.