We report on strong coupling of the charge-carrier plasmon ${\ensuremath{\omega}}_{PL}$ in graphene with the surface-optical phonon ${\ensuremath{\omega}}_{SO}$ of the underlying SiC(0001) substrate with low-electron concentration $(n=1.2\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }{\text{cm}}^{\ensuremath{-}3})$ in the long-wavelength limit $({q}_{\ensuremath{\parallel}}\ensuremath{\rightarrow}0)$. Energy-dependent energy-loss spectra give clear evidence of two coupled phonon-plasmon modes ${\ensuremath{\omega}}_{\ifmmode\pm\else\textpm\fi{}}$ separated by a gap between ${\ensuremath{\omega}}_{SO}({q}_{\ensuremath{\parallel}}\ensuremath{\rightarrow}0)$ and ${\ensuremath{\omega}}_{\text{TO}}({q}_{\ensuremath{\parallel}}⪢0)$, the transverse-optical-phonon mode, in particular, for higher primary electron energies $({E}_{0}\ensuremath{\ge}20\text{ }\text{eV})$. A simplified model based on dielectric theory is able to simulate our energy-loss spectra as well as the dispersion of the two coupled phonon-plasmon modes ${\ensuremath{\omega}}_{\ifmmode\pm\else\textpm\fi{}}$. In contrast, Liu and Willis [Phys. Rev. B 81, 081406(R) (2010)] postulate in their recent publication no gap and a discontinuous dispersion curve with a one-peak structure from their energy-loss data.

Strong phonon-plasmon coupled modes in the graphene/silicon carbide heterosystem

We have re-investigated the well-studied hydrogen covered Si(100) surface using high resolution electron energy loss spectroscopy (HREELS) with a spectral resolution down to 13 cm1, representing an improvement by a factor of 3–4 compared to earlier work. For the first time in HREELS, it has been possible to clearly distinguish between the stretching vibrations of H-Si-Si-H units on monohydride surfaces with a 2×1 low energy electron diffraction pattern, on the one hand, and SiH2 units on dihydride surfaces with 1×1 symmetry on the other hand, the two being shifted by 5 cm-1 with respect to each other, in good agreement with results from infrared spectroscopy. Furthermore, we find trihydride units even for relatively low exposures beyond monohydride saturation coverage from their distinct stretching frequencies, and this points towards early etching stages. The question of the scattering mechanism applicable in our experiments is discussed. Since there are no spectral limitations in HREELS, we can analyze the bending and scissor vibrations with similar accuracy as the stretching vibration. Again, we observe fine structure in our loss peaks, the umbrella mode, for example, giving once more evidence for trihydride species at the surface. The complicated line shape of all vibrational modes can thus be used to deduce detailed structural information about the surface atomic structure, opening up entirely new possibilities by employing HREELS for the structural characterization of (silicon) surfaces with atomic hydrogen as a local probe.

Ultimate resolution electron energy loss spectroscopy at H/Si(100) surfaces

Graphitization of the 6H–SiC(0 0 0 1) surface studied by HREELS

Electron energy loss spectroscopy, in the regime corresponding to losses < 500 meV, is now routinely exploited for the characterisation of material surfaces. Recent instrumental advances and improvements in data analysis enable the study of widely different materials and contributions to the solution of surface and near-surface problems, many of which have a technological importance in fields as diverse as semiconductor devices, molecular sensors and heterogeneous catalysis.

High resolution electron energy loss spectroscopy

We report on the first observation of surface plasmons at a GaN surface by high-resolution electron energy loss (HREEL) spectroscopy. Dipole scattering theory using self-consistent electron density profiles is employed to calculate the surface energy loss function and hence the expected energy loss spectra. The characteristic features of both the surface plasmons and the Fuchs-Kliewer (FK) surface optical phonons are well reproduced in the framework of this model. Fitting measured HREEL spectra allows us to give estimates of important semiconductor parameters such as electron density, electron mobility and band bending. Moreover, it is found that the plasmon damping strongly depends on primary beam energy. Similarly, the FK phonon damping and frequency are also affected by the variation of primary beam energy.

https://iopscience.iop.org/article/10.1088/0268-1242/13/12/011/pdf

Surface plasmons at MOCVD-grown GaN

High-resolution electron-energy-loss spectroscopy was applied to analyze in detail the spatial distribution of dopants in \ensuremath{\delta}-doped (Si) GaAs(100) samples, molecular-beam epitaxially grown at 550 \ifmmode^\circ\else\textdegree\fi{}C with different doping levels and depths. The fitting of the measured energy-loss spectra, based on a smooth self-consistent electron-density profile, reveals that at this growth temperature the silicon atoms are spread symmetrically around the initial doping plane for the doping level of ${\mathit{N}}_{\mathrm{Si}}$=1.3\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. However, the asymmetry in the dopant spreading becomes appreciable for the higher doped sample with ${\mathit{N}}_{\mathrm{Si}}$=6\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. In this case different diffusion coefficients of the dopant atoms were assumed in the growth direction and backward from the initial doping plane in order to obtain better fits to the measured energy-loss spectra. It was found that the damping of the plasmon excitations \ensuremath{\Gamma} changes versus a variation of the primary electron-beam energy ${\mathit{E}}_{0}$ with a significant decrease for the lowest primary energy applied. The observed dependence of \ensuremath{\Gamma} on ${\mathit{E}}_{0}$ is connected with the dominant optical phonon scattering, mostly contributing to the plasmon damping at room temperature. \textcopyright{} 1996 The American Physical Society.

Silicon spreading in delta -doped GaAs(100): A high-resolution electron-energy-loss-spectroscopy study.

Investigation of the space charge regime of epitaxially grown GaAs (100) by high-resolution electron energy-loss spectroscopy

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Silicon spreading in delta -doped GaAs(100): A high-resolution electron-energy-loss-spectroscopy study.

Investigation of the space charge regime of epitaxially grown GaAs (100) by high-resolution electron energy-loss spectroscopy