Electronic Excitations in Graphene in the 1–50 eV Range: The π and π + σ Peaks Are Not Plasmons

• Published in: Nano letters 2014-07, Vol.14 (7), p.3827-3831
• Main Authors: Nelson, Florence J, Idrobo, Juan-Carlos, Fite, John D, Mišković, Zoran L, Pennycook, Stephen J, Pantelides, Sokrates T, Lee, Ji Ung, Diebold, Alain C
• Format: Article
• Language: English
• Subjects: Aberration; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Density functional theory; EELS; Electron states; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Excitation; Excitation spectra; Fullerenes and related materials; diamonds, graphite; Graphene; Materials science; Methods of electronic structure calculations; Physics; Plasmonics; Plasmons; Scanning electron microscopy; Specific materials; Surface and interface electron states
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl500969t

The field of plasmonics relies on light coupling strongly to plasmons as collective excitations. The energy loss function of graphene is dominated by two peaks at ∼5 and ∼15 eV, known as π and π + σ plasmons, respectively. We use electron energy-loss spectroscopy in an aberration-corrected scanning transmission electron microscope and density functional theory to show that between 1 to 50 eV, these prominent π and π + σ peaks are not plasmons, but single-particle interband excitations.