Synthesis and characterization of kinked GaAs nanowires by Sb surfactant

In this study, GaAs/GaSb and GaAs/GaSb/GaAs heterostructure nanowires (NWs) were grown on Si (111) substrates by self-catalyzed vapor-liquid-solid (VLS) mechanism using the ultrahigh vacuum (UHV) molecular beam epitaxy (MBE) system. The GaAs/GaSb/GaAs heterojunction NWs may kink away from [111] to another crystallographic direction, as observed by electron microscopy. The smallest NWs prefer growth along the < 220 > axis, while the larger GaAs NWs chose either < 111 > or < 002 > axis, and the kink angles of 55 degrees, 71 degrees, 109 degrees, 125 degrees, and 145 degrees, respectively. Moreover, significant lateral growth was observed at the GaSb segment in the GaAs/GaSb heterojunction NWs, and lateral growth was clearly evidenced by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray (EDX) techniques. This behavior was attributed to the surfactant effect of Sb, leading to a significant change in the contact angle that ultimately caused the expansion of the Ga droplets. This study is also widely applicable to other III-V nanomaterials and provides conditions for the diversification of optoelectronic devices, such as photodetector or field-effect transistor.