Spin-orbit coupling induced by bismuth doping in silicon thin films

This study demonstrates an enhancement of spin-orbit coupling in silicon (Si) thin films by doping with bismuth (Bi), a heavy metal, using ion implantation. Quantum corrections to conductance at low temperatures in phosphorous-doped Si before and after Bi implantation are measured to probe the increase in spin-orbit coupling, and a clear modification of magnetoconductance signals is observed: Bi doping changes magnetoconductance from weak localization to the crossover between weak localization and weak antilocalization. The elastic diffusion length, phase coherence length, and spin-orbit coupling length in Si with and without Bi implantation are estimated, and the spin-orbit coupling length after Bi doping becomes the same order of magnitude (Lso = 54 nm) with the phase coherence length (Lφ = 35 nm) at 2 K. This is an experimental proof that spin-orbit coupling strength in the thin Si film is tunable by doping with heavy metals.