Growth and transport properties of thin Bi films on InP(110)

Growth and lateral charge transport properties of thin (d = 20-30 Angstrom) Bi films are investigated with scanning tunnelling microscopy. Bismuth is deposited at T=140 K onto the cleaved (110) surface of an InP-based heterostructure. Growth at low temperature is kinetically limited and leads to strained, metastable overlayers. After annealing to 300 K the Bi surface consists of atomically fiat terraces separated by 12 Angstrom deep holes. We find that prolonged injection of a high lateral current promotes significant changes in surface morphology which are attributed to a strain relaxation process mediated by electromigration. Scanning tunnelling potentiometry is applied to probe the local response of the semimetal overlayers to the injected lateral current. The observed potential distribution provides evidence for both phonon and defect scattering. At the position of holes and grain boundaries we find typically 2-4 mV high potential steps. It is argued that these steps indeed reflect a localized increase of the film resistance and cannot be attributed to tip-convolution artefacts.