SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 108: Poster Session VIII: Poster to Mini-Symposium: Frontiers of electronic-structure theory V
O 108.2: Poster
Donnerstag, 4. März 2021, 13:30–15:30, P
Anomalous low-velocity electronic stopping in proton-irradiated graphene — •Alina Kononov1 and Andre Schleife2 — 1Department of Physics, University of Illinois at Urbana-Champaign — 2Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign
Ion beams in high-resolution imaging and patterning techniques can be used efficiently to manipulate and characterize 2D materials. Low particle velocities are particularly interesting, since in this regime the drag force induced on an incident ion by electrons is rife with material-specific effects. Examples include the threshold velocity for semiconductors and insulators below which an ion cannot excite electrons across the band gap and electronic stopping vanishes. In addition, directional bonding in these materials makes electronic stopping sensitive to the ion’s trajectory even for slow ions, when core electrons are negligible. Graphene, thus, presents a highly interesting case with directional bonding but no band gap. Our real-time time-dependent density functional theory simulations of proton-irradiated graphene reveal a shoulder in the low-velocity stopping of channeling protons which does not occur for protons traversing a centroid path. From analyzing the post-impact band occupations and projectile charge state, we infer that resonant charge capture from certain valence bands by channeling protons is responsible for this feature. Our prediction of a new form of anomalous low-velocity stopping has implications for ion beam imaging, where such trajectory-dependent behavior could be exploited to achieve high resolution. (Supported by NSF OAC 17-40219)