Electrical activation and electron spin coherence of ultralow dose antimony implants in silicon

We implanted ultralow doses (2×1011cm−2) of antimony ions (Sb121) into isotopically enriched silicon (Si28) and find high degrees of electrical activation and low levels of dopant diffusion after rapid thermal annealing. Pulsed electron spin resonance shows that spin echo decay is sensitive to the dopant depths, and the interface quality. At 5.2K, a spin decoherence time, T2, of 0.3ms is found for profiles peaking 50nm below a Si∕SiO2 interface, increasing to 0.75ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins.