Electron-spin phase relaxation of phosphorus donors in nuclear-spin-enriched silicon

We report a pulsed electron paramagnetic resonance study of the phase relaxation of electron spins bound to phosphorus donors in isotopically purified ²⁹Si and natural abundance Si (ⁿᵃᵗSi) single crystals measured at 80.3em0exK. The two-pulse echo decay curves for both samples show quadratic dependence on time, and the electron phase relaxation time TM for ²⁹Si is about an order of magnitude shorter than that for ⁿᵃᵗSi. The orientation dependence of TM demonstrates that the phase relaxation is caused by spectral diffusion due to flip-flops of the host nuclear spins. The electron spin echo envelope modulation effects in ²⁹Si are analyzed in the frequency domain.