Epitaxial growth of Bi ultra-thin films on GaAs by electrodeposition

We report on the growth of thin bismuth films on GaAs substrates with different orientations by means of electrochemical deposition. Atomic force microscopy reveals that the films are continuous and exhibit low roughness when they are grown under the appropriate overpotential. ω–2θ X-ray diffraction scans only show reflections that can be indexed as (0 1 L), meaning that Bi grows onto GaAs only in combinations of the (0 0 1) and (0 1 0) orientations. The matching between the GaAs substrate and the Bi layer has been studied by asymmetric X-ray scans, finding that Bi grows epitaxially on GaAs(1 1 0) and GaAs(1 1 1)B, both As-terminated surfaces. We explain these results by structural and chemical considerations.

► Electrodeposition of Bi films on GaAs substrates with different orientations. ► Ultra thin films – 50 nm – are continuous and smooth. ► Bi always grows with (0 1 L) orientations. ► Epitaxial growth onto As terminated surfaces. ► Proposed model based on structural and chemical considerations.