Apparent rippling with honeycomb symmetry and tunable periodicity observed by scanning tunneling microscopy on suspended graphene

Abstract

Suspended graphene is difficult to image by scanning probe microscopy due to the inherent van-der-Waals and dielectric forces exerted by the tip which are not counteracted by a substrate. Here, we report scanning tunneling microscopy data of suspended monolayer graphene in constant-current mode revealing a surprising honeycomb structure with amplitude of 50$-$200 pm and lattice constant of 10-40 nm. The apparent lattice constant is reduced by increasing the tunneling current $I$, but does not depend systematically on tunneling voltage $V$ or scan speed $v_{\mathrm{scan}}$. The honeycomb lattice of the rippling is aligned with the atomic structure observed on supported areas, while no atomic corrugation is found on suspended areas down to the resolution of about $3-4$ pm. We rule out that the honeycomb structure is induced by the feedback loop using a changing $v_{\mathrm{scan}}$, that it is a simple enlargement effect of the atomic resolution as well as models predicting frozen phonons or standing phonon waves induced by the tunneling current. Albeit we currently do not have a convincing explanation for the observed effect, we expect that our intriguing results will inspire further research related to suspended graphene.

10 pages, 7 figures, modified, more detailed discussion on errors in vdW parameters

References in corpus (22)

• The Raman Fingerprint of Graphene
• Two Dimensional Atomic Crystals
• The structure of suspended graphene sheets
• Thermal properties of graphene: Fundamentals and applications
• Atomic Structure of Graphene on SiO2
• Ripple Texturing of Suspended Graphene Atomic Membranes
• Negative Thermal Expansion Coefficient of Graphene Measured by Raman Spectroscopy
• High-Resolution Scanning Tunneling Microscopy Imaging of Mesoscopic Graphene Sheets on an Insulating Surface
• On the roughness of single- and bi-layer graphene membranes
• Finite temperature lattice properties of graphene beyond the quasiharmonic approximation
• Intrinsic and extrinsic corrugation of monolayer graphene deposited on SiO2
• Breakdown of continuum mechanics for nanometer-wavelength rippling of graphene
• Creating One-dimensional Nanoscale Periodic Ripples in a Continuous Mosaic Graphene Monolayer
• A Review on Flexural Mode of Graphene: Lattice Dynamics, Thermal Conduction, Thermal Expansion, Elasticity, and Nanomechanical Resonance
• Unusual ultralow frequency fluctuations in freestanding graphene
• Anomalous Dynamical Behavior of Freestanding Graphene Membranes
• Thermal mirror buckling in freestanding graphene locally controlled by scanning tunneling microscopy
• Pseudomagnetic Fields in a Locally Strained Graphene Drumhead
• Anharmonic effects in the optical and acoustic bending modes of graphene
• Scanning Tunneling Microscopy and Spectroscopy of Graphene on Insulating Substrates
• Preferential antiferromagnetic coupling of vacancies in graphene on SiO_2: Electron spin resonance and scanning tunneling spectroscopy
• Broad frequency and amplitude control of vibration in freestanding graphene via scanning tunneling microscopy with calculated dynamic pseudo-magnetic fields

Cited by in corpus (1)

• Thermal ripples in bilayer graphene