QDev Seminar: Dr. Jung-Hyun (Jordan) Kang

The Unique Properties in MBE Growth of Gold Assisted InAs Nanowires on the (001) Substrates

This talk concentrates on the benefits of growth of InAs nanowires (NWs) on the (001) surface. Growth of bare merging nanowires can lead to the formation of nanowires intersections, two dimensional plates formed at the intersections, and in-situ aluminium (Al) side-coating. Based on the nanowire intersections formed by merging of two wurtzite (WZ) wires growing opposite <111> directions towards each other, the new pure zinc blende (ZB) nanowire nucleates at the intersection, growing in the [00-1] direction towards the substrate. Two dimensional plates occasionally form between the ZB and one of the WZ wires (Figure 1a). The plates assuming a pure WZ structure form a periodic “staircase” interface with the ZB wire emerging between the two WZ wires where each step is constructed of 6 In-As WZ monolayers perfectly matched to the ZB structures. This periodic matching of 6 In-As monolayers corresponds to the phase transition of the WZ to the ZB structure in the {110} plane with a mismatch of 0.4% (Figure 1b). In-situ Al coating of InAs NWs providing an intimate contact between the InAs NW and the superconducting metal has lately become a crucial ingredient in the formation of superconductor-semiconductor hybrid devices as key role players in the study for Majorana zero modes. The prominent tilt angle of nanowires grown on the (001) surface makes this process significantly more feasible allowing for continuous and uniform Al shell side coating (shown in Figure 1c).

Figure 1. (a) a SEM image of the interconnected InAs NWs and as-grown 2 dimensional plate, (b) a HR-TEM image of the interface between the ZB wire and the WZ plate, and (c) a SEM image of the in-situ Al coated InAs NWs grown on InAs (001).