Vertically Aligned GaAs Nanowires on Graphite and Few-Layer Graphene: Generic Model and Epitaxial Growth

Abstract

By utilizing the reduced contact area of nanowires, we show that epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved. A generic atomic model is presented which describes the epitaxial growth configurations applicable to all conventional semiconductor materials. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene by the self-catalyzed vapor-liquid-solid technique using molecular beam epitaxy. A two-temperature growth strategy was used to increase the nanowire density. Due to the self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Electron microscopy studies reveal an epitaxial relationship of the grown nanowires with the underlying graphitic substrates. Two relative orientations of the nanowire side-facets were observed, which is well explained by the proposed atomic model. A prototype of a single GaAs nanowire photodetector demonstrates a high-quality material. With GaAs being a model system, as well as a very useful material for various optoelectronic applications, we anticipate this particular GaAs nanowire/graphene hybrid to be promising for flexible and low-cost solar cells.

Architectured van der Waals epitaxy of ZnO nanostructures on hexagonal BN

“…[32][33][34] Recent works on epitaxy of III-V nanowires on graphene also discussed the possible rotated in-plane epitaxial relationships or different nanowire growth directions presumably caused by lattice mismatch when covalent epitaxial links exist at the heterointerface. 35,36 Hence, it is strongly suggested that the observed domain-aligned heteroepitaxial relationship of ZnO/hBN should result from weakly bound vdW heterointerfaces.…”

Catalyst-free growth of InAs/InxGa1−xAs coaxial nanorod heterostructures on graphene layers using molecular beam epitaxy

“…Inset (ii) of Figure 2c shows that the position of the (10) streak from CVD graphene layers was aligned indistinguishably with that of 112l À Á InAs Bragg spots, implying a possible in-plane, lattice-matching configuration of InAs crystals and graphene layers. 16,21 For longer growth times approaching 1 h and InAs nanorod lengths reaching 10 μm, sharp spots were clearly visible in the RHEED patterns (Figure 2b) thanks to the transmission mode of RHEED. 22 For all azimuthal rotation angles, the RHEED patterns from the InAs nanorods were the same, indicating that the nanorods were vertically well aligned along [0002] WZ and [111] ZB , but their in-plane orientations were random; these results were attributed to in-plane misorientations of grains in the CVD graphene layers.…”

“…For catalyst-free growth of InAs nanorods, we supplied As 4 to the substrates for 10 min before supplying In to prevent In droplet formation on the graphene layers, which resulted in quite different nucleation and crystal growth behavior from vapor-liquid-solid (VLS) growth. 14,16 After the preparation of InAs nanorods, InAs/In x Ga 1 − x As coaxial nanorod heterostructures were subsequently synthesized by heteroepitaxial growth of an In x Ga 1 − x As thin layer on InAs core nanorods. Deposition of In x Ga 1 − x As coaxial shell layers was performed at 380°C for 1 h by the addition of a gallium (Ga) molecular beam, resulting in an In x Ga 1 − x As layer coating over the entire InAs nanorod surface.…”

“…This image reveals that the dislocations were not concentrated close to the interface; this outcome would be attributed to the heteroepitaxial relationship between the graphene layers and InAs. 6,16,19 The crystal structure of In x Ga 1 − x As /InAs coaxial nanorod heterostructures was investigated by HR-TEM images near the zone axis of 1010…”

Scalable ZnO nanotube arrays grown on CVD-graphene films

“…15 On the other hand, previous reports of growth on graphene deposited by chemical vapor deposition (CVD-graphene) have shown unsatisfactory growth controllability, with a lack of individual position control (i.e., a bundled growth), low growth selectivity, or poor vertical alignment. 16,17 Herein, we report a method to significantly enhance the growth controllability on CVD-graphene, enabling a wafer-scale preparation of individually position-controlled and vertically aligned 1D ZnO nanostructure arrays on arbitrary substrates including amorphous, metallic, or flexible substrates. The growth behaviors of semiconductor nanostructures on exfoliated and CVD-graphene are drastically different, which has led to different strategies for achieving position-controlled growth.…”