Variation of energy gap and resistivity minimum position with thickness in bismuth thin films

Bismuth thin films of different thicknesses between about 20 and 225 nm are vacuum deposited at room temperature in a vacuum of 3 × 10−3 Pa. The films are heat‐treated “in situ” and the resistances monitored. It is found that the resistivity‐temperature plots of the films after heat‐treatment are non‐linear and exhibit a minimum whose position is a function of thickness. It is also found that the films behave as semiconductors, the band gap decreasing with increasing thickness. The observations are interpreted on the basis of quantum size effect and the limitation of the electronic mean free path by the grain size of the films. Copyright © 1982 WILEY‐VCH Verlag GmbH & Co. KGaA