Nanostructures in suspended mono- and bilayer epitaxial graphene

Abstract

Suspended graphene membrane presents a particular structure with fundamental interests and applications in nanomechanics, thermal transport and optoelectronics. Till now, the commonly used geometries are still quite simple and limited to the microscale. We propose here to overcome this problem by making nanostructures in suspended epitaxial bilayer graphene on a large scale and with a large variety of geometries. We also demonstrate a new hybrid thin film of SiC-graphene with an impressive robustness. Since the mechanics and thermal dissipation of a suspended graphene membrane are strongly related to its own geometry, we have in addition focused on thermal transport and strain engineering experiments. Micro-Raman spectroscopy mapping was successfully performed for various geometries with intrinsic properties measurements at the nanoscale. Our engineering of graphene geometry has permitted to reduce the thermal transport, release and modulate the strain in our structures.

Nanomechanical Strain Concentration on a Two-Dimensional Nanobridge within a Large Suspended Bilayer Graphene for Molecular Mass Detection

“…For sample manufacture, we used epitaxial bilayer graphene grown by sublimation on a SiC substrate at 900°C as in Figure 1a. We previously demonstrated our experience in nanostructuring and suspending a complex design in our graphene over a large distance 24 . By e-beam lithography, we patterned the graphene into large structures composed of two opposed triangles connected by a small nano-bridge.…”

“…During the etching, we took care to avoid bubbles during the etching in KOH at 50°C and under UV light >0.5mW. Details are described elsewhere 24 . We etched around 8 µm of SiC with this technic at speed of 2µm/hour.…”

“…The simplest and most versatile tool to measure strain in suspended 2D materials is Raman spectroscopy 23,24 . Measurements with scanning tunneling spectroscopy 13,25 or transmission electron microscopy 19 are spatially resolved but difficult to implement for suspended 2D materials on a chip and are limited experimentally and environmentally.…”

Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC

“…The D’ band is assigned to an intravalley scattering, where only transitions on the same Dirac cone are considered. The 2D’ band is the second order process of the D’ band [ 105 , 106 ]. The 2D’ mode does not require an intravalley momentum transfer for its activation.…”

“…The shape of the 2D band can be predicted accurately by the double-resonance model which can be used to identify the number of atomic planes present in graphene. Specifically, the deconvolution of the 2D band into elemental bands gives the number of atomic layers [ 26 , 103 , 104 , 105 , 106 , 107 , 108 ]. For example, in a bilayer the 2D band is split into four bands—making the 2D band wider [ 103 ].…”