Large magnetoresistance in postannealed Bi thin films

We have observed a large increase in the magnetoresistance (MR) of molecula r beam epitaxy grown Bi thin films, which were subjected to a postannealing procedure 3 degreesC below the Bi melting point. We have achieved an incre ase in the MR by a factor of 2560 at helium temperatures compared with of 3 43 for an as-grown film. The enhancement of the MR in the annealed films is due to higher electron and hole mobilities (mu (e)approximate to 1x10(6) c m(2)/V s at 5 K) relative to those of the as-grown films (mu (e)approximate to 9x10(4) cm(2)/V s at 5 K). The enhancement of the mobility in the annea led films is also supported by the observation of Shubnikov-de Haas oscilla tions. (C) 2001 American Institute of Physics.