Letter pubs.acs.org/NanoLett
Wurtzite/Zinc-Blende ‘K’-shape InAs Nanowires with Embedded TwoDimensional Wurtzite Plates Jung-Hyun Kang,*,† Marta Galicka,‡ Perla Kacman,‡ and Hadas Shtrikman† †
Dept. of Condensed Matter Physics, Braun Center for Submicron Research, Weizmann Institute of Science, Rehovot 76100, Israel Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
‡
S Supporting Information *
ABSTRACT: The prediction that Majorana Fermions obey nonabelian exchange statistics can only be tested by interchanging such carriers in “Y’- or ‘X’- (or ‘K’-) shaped nanowire networks. Here we report the molecular beam epitaxy (MBE) growth of ‘K’-shaped InAs nanowires consisting of two interconnected wurtzite wires with an additional zinc-blende wire in between. Moreover, occasionally, the growth results in formation of a purely wurtzite twodimensional plate between the zinc-blende nanowire and one (sometimes both) intersecting wurtzite arm. By modeling the crystal structure we explain the transformation from wurtzite to zinc-blende and the coexistence of both crystallographic phases in such nanowire structures. To the best of our knowledge neither the MBE growth of an InAs nano-object showing combination of wurtzite and zinc-blende crystal structures nor the growth of pure wurtzite InAs nanoplates in this geometry has been reported before. KEYWORDS: MBE, InAs, nanowires, NW intersections, nanoplate, crystal phase transition, phase combination growing along two different ⟨111⟩ directions on (001)B InAs substrate merge.22 Similar results were obtained on (001)B InP23 and (001) Si24 substrates using predesigned ‘V’-groove patterns. Electrical properties of such intersections were demonstrated using multiprobe measurements.22,24 In this study, we demonstrate formation of a ‘K’-shaped NW intersection by merging of two WZ InAs wires into a ‘Y’-shape configuration, which is followed by growth of an additional zinc-blende (ZB) wire between the WZ ones. Moreover, occasionally, two-dimensional (2D)-plates subsequently form between the ZB wire and one of the WZ arms; sometimes on both sides of the ZB NW. By modeling the crystal structure we explain the transformation from WZ to ZB and combination of WZ and ZB crystal structures in such NW structures. In our study we were able not only to repeatedly obtain the ‘K’-shaped NWs but also to address the trimming between the 2D-plate and the wires enclosing it. Our growth provides a feasible way for producing InAs free-standing plates interconnected to two InAs NWs, which can be used in mesoscopic physics experiments particularly given their extremely pure WZ structure. Methods. InAs NWs constructing the intersections were grown by the gold-assisted, vapor−liquid−solid (VLS) or vapor−solid−solid (VSS) process in a high purity molecular beam epitaxy (MBE) system. The epi-ready (001)B InAs
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n the last couple of decades a variety of nanosized semiconductor structures with potential for serving as a basis for numerous applications and for studying state of the art effects in mesoscopic physics, have been reported: nanomembranes,1 nanoribbons,2 nanotrees,3 nanoflowers,4 and nanowires (nanowhiskers). Especially, nanowires (NWs) have become the focus of many studies perusing nanocomponents for future integrated devices. Due to the excellent electrical and optical properties of III−V compound semiconductors, most of the reported nanoscale electronic and optoelectronic devices, such as p−n junctions5 and field effect transistors,6 light emitting diodes,7 photodetectors,8 nanolasers,9 photovoltaic solar-cells,10 etc., were based on III−V NWs. In addition, recently, III−V semiconductor NWs have been suggested as a promising platform for the emergence of Majorana Fermions.11,12 Indeed, InAs and InSb NWs, due to their strong spin−orbit coupling and Zeeman splitting, have become key ingredients of hybrid semiconductor/superconductor devices used in the quest of Majorana Fermions.13−15 Finally, it has been suggested that a network of “T’- or ‘X”-shaped III−V NWs is required for experiments, which would demonstrate the predicted nonabelian exchange statistics of Majorana Fermions.16,17 Among numerous studies of distinctive morphology and crystal structures of NWs,18−21 InAs NW networks were first investigated by Dick et al.21 Later, InAs NWs intersections with the aim to form NW interconnections have been reported.22−24 We looked into the structural transition, which is typical of intersections formed when two wurtzite (WZ) InAs NWs © XXXX American Chemical Society
Received: November 3, 2016 Revised: December 5, 2016 Published: December 21, 2016 A
DOI: 10.1021/acs.nanolett.6b04598 Nano Lett. XXXX, XXX, XXX−XXX
Letter
Nano Letters substrate, glued with indium onto a (two sided) lapped Si wafer, was initially heated in the introduction chamber to ∼200 °C for water desorption and then degassed at ∼400 °C overnight. This was followed by oxide blow-off in a dedicated treatment chamber (attached to the MBE system), where a thin layer of gold (
