Tailoring the electronic structure of thin Bi films via the growth on vicinal Ge(111)

Abstract

The realization of a regular distribution of defects or step edges with a specific orientation at the surface of a semiconductor or a semimetal, such as Bi, might have interesting implications for both fundamental studies and applications, due to the electronic properties stemming from their peculiar topology. Here we present an accurate comparison of the morphological and electronic structure of thin Bi film (with a thickness of 10 nm) grown on Ge(111) and on a high index Ge(111) vicinal surface, Ge(223). We make use of low energy electron diffraction (LEED) and spin-resolved photoemission spectroscopy (SR-PES) for the crystallographic and electronic characterization, respectively. We show that on both substrates it is possible to grow thin Bi films showing the hexagonal Bi(111) surface orientation, whose spin-resolved electronic structure is reminiscent of the one characteristic of bulk Bi(111). At variance with the films grown on Ge(111), those grown on Ge(223) present some specific features, namely the presence of a splitting in the LEED diffraction spots and a reduced momentum dispersion of the electronic states. We interpret these features as evidences that the peculiar morphology of the substrate can be indeed used to modulate the growth of the Bi film leading to the formation of a stepped Bi surface.