Role of the surface states in the magnetotransport properties of ultrathin bismuth films

We have investigated the magnetotransport properties of ultrathin films of Bi grown on thermally oxidized Si(001) substrates with thickness ranging from 10 to 100 nm at temperatures down to 2 K and in magnetic fields up to 90 kOe. Remarkable differences both in temperature and field dependence of the Hall resistivity are found for the films with thickness above and below 20 nm. These observations can be explained due to the presence of surface states, which play an important role in determining the electronic transport properties of the thinnest films. The estimated surface carrier density 4 x 10^(13) cm^(-2) at room temperature correlates well with that recently reported from angle-resolved photoemission spectroscopy on ultrathin Bi(001) films.