Semimetal-to-semiconductor transition in bismuth thin films

Field- and temperature-dependent magnetotransport measurements on Bi layers grown by molecular-beam epitaxy have been analyzed by mixed-conduction techniques. In the thin-film limit, the net hole density scales inversely with layer thickness while the mobility scales linearly. By studying the minority electron concentration as a function of temperature in the range 100-300 K, we have unambiguously confirmed the long-standing theoretical prediction that quantum confinement should convert Bi from a semimetal to a semiconductor at a critical thickness on the order of 300.