Local Plasmon Engineering in Doped Graphene

Abstract

Single-atom B or N substitutional doping in single-layer suspended graphene, realized by low-energy ion implantation, is shown to induce a dampening or enhancement of the characteristic interband π plasmon of graphene through a high-resolution electron energy loss spectroscopy study using scanning transmission electron microscopy. A relative 16% decrease or 20% increase in the π plasmon quality factor is attributed to the presence of a single substitutional B or N atom dopant, respectively. This modification is in both cases shown to be relatively localized, with data suggesting the plasmonic response tailoring can no longer be detected within experimental uncertainties beyond a distance of approximately 1 nm from the dopant. Ab initio calculations confirm the trends observed experimentally. Our results directly confirm the possibility of tailoring the plasmonic properties of graphene in the ultraviolet waveband at the atomic scale, a crucial step in the quest for utilizing graphene's properties toward the development of plasmonic and optoelectronic devices operating at ultraviolet frequencies.

Single-atom vibrational spectroscopy in the scanning transmission electron microscope

“…Vibrational electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) has recently emerged as a powerful means of probing the vibrational response of materials at a spatial resolution superior to other experimental techniques (9,10). Tip-enhanced Raman spectroscopy (TERS) (11) or inelastic electron tunneling spectroscopy 20 (IETS) (12,13) provide high spatial and energy resolution alternatives, but they are strictly limited to surface experiments and therefore present challenges for a range of applications. Vibrational STEM-EELS on the other hand takes advantage of versatile probe-forming optics to offer ground-breaking capabilities: nanometer-scale thermometry (14), mapping of bulk and surface-phonon-polariton modes (15), establishing phonon dispersion diagrams from nano-25 objects (16), site-specific isotopic labeling in molecular aggregates (17).…”

“…As discussed 15 therein, the important features observed in the vibrational EEL spectra of graphene can safely be interpreted in terms of the phonon density of states (DOS) of the bulk. The local behavior of the DOS can be quantified by the projected phonon DOS (PPDOS) defined as ( ) = | | ( ), where denotes a specific atom, and are the phonon angular frequency and normalized polarization, and the sum is carried over all the phonon modes of the 20 supercell. Since in our experiments the momentum transfer occurs predominantly in the plane perpendicular to the electron beam trajectory, only the components of the phonon polarization parallel to the graphene plane are relevant.…”

Localized Plasmon Response Engineering in B- and N-Doped Graphene

“…However, practical computational limitations restrict supercell sizes and prevent us from achieving the same match quality in low loss simulations as for core loss calculations [4]. Nevertheless, our results directly confirm the possibility of tailoring the plasmonic properties of graphene in the ultraviolet waveband, at the atomic scale, a crucial step in the quest for utilising graphene's properties towards the development of plasmonic and optoelectronic devices operating at ultraviolet frequencies [3,5].…”

“…A relative 16% decrease or 20% increase in the π plasmon quality factor is attributed to the presence of a single substitutional B or N atom dopant respectively. This modification is in both cases shown to be relatively localised, with data suggesting the plasmonic response tailoring can no longer be detected within experimental uncertainties beyond a distance of approximately 1 nm from the dopant [3].…”

Phonon-assisted processes in the ultraviolet-transient optical response of graphene

“…Electronic properties of such systems are shown to be highly sensitive to external perturbation that introduces excess electron or hole concentrations. For instance, electrostatic and chemical doping techniques were successfully utilized in order to tune optical absorption as well as plasmon and exciton energies in graphene-based materials [3][4][5][6][7][8][9], transitions metal dichalcogenides [10][11][12][13][14][15][16], and corresponding van-der-Waals heterostructures [17,18].…”