title: Graphene flakes under controlled biaxial deformation.
abstract: Thin membranes, such as monolayer graphene of monoatomic thickness, are bound to exhibit lateral buckling under uniaxial tensile loading that impairs its mechanical behaviour. In this work, we have developed an experimental device to subject 2D materials to controlled equibiaxial strain on supported beams that can be flexed up or down to subject the material to either compression or tension, respectively. Using strain gauges in tandem with Raman spectroscopy measurements, we monitor the G and 2D phonon properties of graphene under biaxial strain and thus extract important information about the uptake of stress under these conditions. The experimental shift over strain for the G and 2D Raman peaks were found to be in the range of 62.3 ± 5 cm(-1)/%, and 148.2 ± 6 cm(-1)/%, respectively, for monolayer but also bilayer graphenes. The corresponding Grüneisen parameters for the G and 2D peaks were found to be between 1.97 ± 0.15 and 2.86 ± 0.12, respectively. These values agree reasonably well with those obtained from small-strain bubble-type experiments. The results presented are also backed up by classical and ab initio molecular dynamics simulations and excellent agreement of Γ-E2g shifts with strains and the Grüneisen parameter was observed.
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.|Department of Materials Science, University of Patras, Patras, 26504 Greece.
authors.forename: Charalampos
authors.initials: C
authors.lastname: Androulidakis
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.
authors.forename: Emmanuel N
authors.initials: EN
authors.lastname: Koukaras
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.
authors.forename: John
authors.initials: J
authors.lastname: Parthenios
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.|Department of Materials Science, University of Patras, Patras, 26504 Greece.|Crete Center for Quantum Complexity and Nanotechnology (CCQCN), Physics Department, University of Crete, 71003 Heraklion, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Kalosakas
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.|Department of Materials Science, University of Patras, Patras, 26504 Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Papagelis
authors.affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.|Department of Chemical Engineering, University of Patras, Patras 26504 Greece.
authors.forename: Costas
authors.initials: C
authors.lastname: Galiotis