Abstract
In this paper, we demonstrated the growth of GaAs/GaSb core-shell heterostructured nanowires on GaAs substrates, with the assistance of Au catalysts by molecular-beam epitaxy. Time-evolution experiments were designed to study the formation of GaSb shells with different growth times. It was found that, by comparing the morphology of nanowires for various growth times, lateral growth was taking a dominant position since GaSb growth began and bulgy GaSb particles formed on the nanowire tips during the growth. The movement of catalyst Au droplets was witnessed, thus, the radial growth was enhanced by sidewall nucleation under the vapor-solid mechanism due to the lack of driving force for axial growth. Moreover, compositional and structural characteristics of the GaAs/GaSb core-shell heterostructured nanowires were investigated by electron microscopy. Differing from the commonly anticipated result, GaSb shells took a wurzite structure instead of a zinc-blende structure to form the GaAs/GaSb wurzite/wurzite core-shell heterostructured nanowires, which is of interest to the research of band-gap engineering. This study provides a significant insight into the formation of core-shell heterostructured nanowires.
Highlights
The Au conventional growth, we found that the particle on the NW top is GaSb rather than the Au alloy catalyst, meaning that the Au droplet has moved away from the NW top
GaAs/GaSb NWs were grown on GaAs(111)B substrates by Riber-32 R@D molecular-beam epitaxy (MBE) system with
The substrate was transferred into an Au evaporation chamber, which is a buffer chamber of a typical Riber MBE system, and an ultra-thin Au film was deposited on the substrate at room temperature from the Knudsen cell
Summary
III-V semiconductor nanowires (NWs) have been studied extensively in recent years due to their unique physical properties [1,2] and, in turn, have been used in a wide range of applications, including solar cells [3,4,5], nanolasers [6], infrared detectors [7,8,9], and quantum computing [10,11]. With their growth feature of being free-standing, NWs can withstand much higher lattice mismatch, since the strain at the hetero-interface between two different materials can be elastically relieved [12]. VLS mechanism has been the most widely used mechanism for NW growth because it helps to synthesize axial [16,17] and branched heterostructure NWs [18] with
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