Large surface-state conductivity in ultrathin Bi films

In situ microscopic-four-point probe conductivity measurements were performed for ultrathin Bi films on Si(111)-7×7. From the extrapolation of thickness-dependent conductivity and decrease in conductivity through surface oxidization, we found clear evidence of large surface-state conductivity (σ_SS∼1.5×10^-3Ω^-1/◻ at room temperature) in Bi(001) films. For the thinnest films (∼25Å ), the transport properties are dominated by the highly inert surface states that are Rashba spin-split, and this suggests the possibility of using these Bi surface states for spintronics device application.