Abstract
Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realising graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron–phonon excitations, further influencing phonon-assisted inelastic electron tunnelling.
Highlights
Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities
Phonons in graphene can be excited by tunnelling electrons from a tip through the use of scanning tunnelling microscopy (STM), and the electron–phonon coupling is revealed as an enhancement of electron tunnelling to graphene states with energies larger than the phonon energy
These modifications manifest as a gap-like feature at the Fermi level in the tunnelling spectra obtained via scanning tunnelling spectroscopy measurements[9,10,11,12]
Summary
Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. We choose nanobubbles as the structural ‘knob’, that is, an on-off switch for phonon control, and exploit the fact that noble-gas ions can penetrate below the first atomic layer of a graphite surface to form interstitial defects by low-energy impinging[13,14,15]. The experimentally observed protrusions in the Ar þ -ion irradiated graphene can in general be attributed to several origins such as adatom adsorption, vacancy-induced deformation[16] and nanobubble formation by noble-gas-atom implantation[13,14,15].
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