Metastability of Bi Films Mediated by Surface Kinetics

We report on a structural phase transformation of bismuth films deposited on Si(111)-(7X7). Films with thicknesses 20 to $\sim $100 angstroms, upon annealing, first order into a metastable pseudocubic phase and then transform into a stable rhombohedral phase. The two phases have very different electronic band structures as measured by angle-resolved photoemission spectroscopy. The formation of the metastable phase over a wide thickness range can be attributed to a surface nucleation mechanism.