4 research outputs found
Synthesis of quasi-free-standing bilayer graphene nanoribbons on SiC surfaces
Scaling graphene down to nanoribbons is a promising route for the implementation of this material into devices. Quantum confinement of charge carriers in such nanostructures, combined with the electric field-induced break of symmetry in AB-stacked bilayer graphene, leads to a band gap wider than that obtained solely by this symmetry breaking. Consequently, the possibility of fabricating AB-stacked bilayer graphene nanoribbons with high precision is very attractive for the purposes of applied and basic science. Here we show a method, which includes a straightforward air annealing, for the preparation of quasi-free-standing AB-bilayer nanoribbons with different widths on SiC(0001). Furthermore, the experiments reveal that the degree of disorder at the edges increases with the width, indicating that the narrower nanoribbons are more ordered in their edge termination. In general, the reported approach is a viable route towards the large-scale fabrication of bilayer graphene nanostructures with tailored dimensions and properties for specific applications
Coincident-site lattice matching during van der Waals epitaxy
Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb2Te3 films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6√3 × 6√3)R30° buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb2Te3 /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate that depend on the size of the surface unit cell. This demonstrates that there is a significant, although relatively weak, interfacial interaction between the two materials. Lattice matching is thus relevant for vdW epitaxy with two 2D bonded materials and a fundamental design parameter for vdW heterostructures
Molecular Beam Epitaxy of GaN Nanowires on Epitaxial Graphene
We demonstrate an
all-epitaxial and scalable growth approach to
fabricate single-crystalline GaN nanowires on graphene by plasma-assisted
molecular beam epitaxy. As substrate, we explore several types of
epitaxial graphene layer structures synthesized on SiC. The different
structures differ mainly in their total number of graphene layers.
Because graphene is found to be etched under active N exposure, the
direct growth of GaN nanowires on graphene is only achieved on multilayer
graphene structures. The analysis of the nanowire ensembles prepared
on multilayer graphene by Raman spectroscopy and transmission electron
microscopy reveals the presence of graphene underneath as well as
in between nanowires, as desired for the use of this material as contact
layer in nanowire-based devices. The nanowires nucleate preferentially
at step edges, are vertical, well aligned, epitaxial, and of comparable
structural quality as similar structures fabricated on conventional
substrates