Dynamic nuclear polarization (DNP) of 29Si nuclear spins induced by saturation of electron paramagnetic resonance (EPR) transitions of lithiumrelated centers in float zone (FZ) grown silicon is reported. Both isolated Li and Li-O complex centers showed strong EPR absorption lines in the temperature range 3.4-10 K and led to very efficient orientation of 29Si nuclear spins. The temperature dependence and time constant of 29Si DNP are investigated in detail. The 29Si DNP of 0.72% was achieved at 3.4 K by excitation of the Li-O forbidden EPR transition underillumination, corresponding to a ∼352 fold increase with respect to the thermal equilibrium polarization.
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