Anomalous stopping and charge transfer in proton-irradiated graphene

TL;DR

This paper reveals a novel low-velocity stopping effect in proton-irradiated graphene, linked to electron capture, with implications for ion microscopy imaging contrast.

Contribution

It introduces a new anomalous stopping phenomenon in graphene due to electron capture, supported by first-principles calculations.

Findings

Shoulder feature in stopping power for channeling protons

Backward electron emission is more sensitive to proton trajectory

Steep drop in electron emission for slow protons

Abstract

We use first-principles calculations to uncover and explain a new type of anomalous low-velocity stopping effect in proton-irradiated graphene. We attribute a shoulder feature that occurs exclusively for channeling protons to enhanced electron capture from $\sigma$+$\pi$ orbitals. Our analysis of electron emission indicates that backward emission is more sensitive to proton trajectory than forward emission and could thus produce higher contrast images in ion microscopy. For slow protons, we observe a steep drop in emission, consistent with predictions from analytical models.