Pulsed EPR study of spin coherence time of P donors in isotopically controlled Si

We investigate spin coherence time of electrons bound to phosphorus donors in silicon single crystals. The samples are isotopically controlled so that they may possess various concentrations (from 4.7% to 99.2%) of 29Si, which is the only non-zero-spin stable isotope of silicon. The orientation dependence of electron-spin coherence times are presented, and electron spin echo envelope modulation is analyzed in time-frequency space.