Resonance Raman Spectroscopy of Silicene and Germanene

Abstract

We model Raman processes in silicene and germanene involving scattering of quasiparticles by, either, two phonons, or, one phonon and one point defect. We compute the resonance Raman intensities and lifetimes for laser excitations between 1 and 3 eV using a newly developed third-nearest neighbour tight-binding model parametrized from first principles density functional theory. We identify features in the Raman spectra that are unique to the studied materials or the defects therein. We find that in silicene, a new Raman resonance arises from the 2.77 eV π − σ plasmon at the M point, measurably higher than the Raman resonance originating from the 2.12 eV π plasmon energy. We show that in germanene, the lifetimes of charge carriers, and thereby the linewidths of the Raman peaks, are influenced by spin-orbit splittings within the electronic structure. We use our model to predict scattering cross sections for defect induced Raman scattering involving adatoms, substitutional impurities, Stone-Wales pairs, and vacancies, and argue that the presence of each of these defects in silicene and germanene can be qualitatively matched to specific features in the Raman response.

RHEED Study of the Epitaxial Growth of Silicon and Germanium on Highly Oriented Pyrolytic Graphite

“…This is consistent with the previous report on germanene, where Jung et al revealed a Raman band at 296 cm −1 in a germanene sample [52]. This line was also predicted theoretically by Kukucska et al [53]. The rest of the spectrum corresponded to the spectrum of the HOPG substrate.…”

The Expanding Frontiers of Tip-Enhanced Raman Spectroscopy

“…234 However, experimental studies were rarely reported on Raman characterization of germanene, although its vibrational properties have been investigated by means of first-principles calculations. 235,236 Recently, germanene sheets have been epitaxially prepared on Ag(111) films supported on Ge(111) 237 and on hexagonal (h)-AlN grown on Ag(111), 238 affording researchers the opportunities to perform TERS studies on its vibrational properties and interactions with the underlying substrates.…”

Optical scanning tunneling microscopy based chemical imaging and spectroscopy

“…Moving beyond carbon and silicon, germanene, a planar germanium allotrope has been grown on supporting surfaces by molecular beam epitaxy [133][134][135][136][137]. However, its vibrational properties have thus far only been investigated with first-principle calculations [138,139]. Metal-supported ultrathin oxide films are other types of functionalized substrates, which have been extensively studied in the fields of physical chemistry and model catalysis [140][141][142].…”