Enhancement of spin signals by thermal annealing in silicon-based lateral spin valves

The effect of thermal annealing on spin accumulation signals in silicon (Si)-based lateral spin devices is investigated. The annealing is carried out after fabrication of the spin devices, which allows us to directly compare the spin-related phenomena before and after annealing. The magnitude of non-local four-terminal signals (Delta V-nl) at room temperature is increased more than two-fold after annealing at 300 degrees C for 1 h. The channel length dependence of Delta V-nl and the Hanle signals reveal that the spin polarization of the ferromagnetic contact is increased by the annealing. In contrast, the spin diffusion length and spin lifetime in the Si channel do not change.