Comparison of charged particle energy loss in epitaxial with free-standing multilayer graphene

TL;DR

This paper develops a formalism to analyze how a charged particle loses energy when passing through multilayer graphene, comparing epitaxial and free-standing types, and explores the effects of substrate-induced energy gaps on plasma oscillations and energy loss.

Contribution

It introduces a new formalism for calculating energy loss in multilayer graphene considering substrate effects and applies it to interpret experimental EELS data.

Findings

Energy gap increases plasmon wave number range and red-shifts stopping power.

Substrate-induced gaps significantly alter plasma oscillation characteristics.

Formalism successfully explains features observed in experimental EELS data.

Abstract

We present a formalism and numerical results for the energy loss of a charged particle scattered at an arbitrary angle from epitaxially grown multilayer graphene (MLG). It is compared with that of free-standing graphene layers. Specifically, we investigated the effect of the substrate induced energy gap on one of the layers. The gap yields collective plasma oscillations whose characteristics are qualitatively and quantitatively different from those produced by Dirac fermions in gapless graphene. The range of wave numbers for undamped self-sustaining plasmons is increased as the gap is increased, thereby increasing and red-shifting the MLG stopping power for some range of charged particle velocity. We also applied our formalism to interpret several distinct features of experimentally obtained electron energy loss spectroscopy (EELS) data.