Merging Nanowires and Formation Dynamics of Bottom-Up Grown InSb Nanoflakes

Indium Antimonide (InSb) is a semiconductor material with unique properties, that are suitable for studying new quantum phenomena in hybrid semiconductor-superconductor devices. The realization of such devices with defect-free InSb thin films is challenging, since InSb has a large lattice mismatch with most common insulating substrates. Here, the controlled synthesis of free-standing 2D InSb nanostructures, termed as nanoflakes, on a highly mismatched substrate is presented. The nanoflakes originate from the merging of pairs of InSb nanowires grown in V-groove incisions, each from a slanted and opposing {111}B facet. The relative orientation of the two nanowires within a pair, governs the nanoflake morphologies, exhibiting three distinct ones related to different grain boundary arrangements: no boundary (type-I), sigma 3- (type-II), and sigma 9-boundary (type-III). Low-temperature transport measurements indicate that type-III nanoflakes are of a relatively lower quality compared to type-I and type-II, based on field-effect mobility. Moreover, type-III nanoflakes exhibit a conductance dip attributed to an energy barrier pertaining to the sigma 9-boundary. Type-I and type-II nanoflakes exhibit promising transport properties, suitable for quantum devices. This platform hosting nanoflakes next to nanowires and nanowire networks can be used to selectively deposit the superconductor by inter-shadowing, yielding InSb-superconductor hybrid devices with minimal post-fabrication steps.

Automated summary

This paper presents a method for synthesizing free-standing InSb nanostructures on mismatched substrates and investigates their properties. The morphology of the nanostructures depends on the relative arrangement of two nanowires, with type I and type II nanostructures exhibiting promising transport properties for quantum devices. This platform can be used to selectively deposit superconductors and fabricate InSb-superconductor hybrid devices.