Reconstruction of Zigzag Graphene Edges: Energetics, Kinetics and Residual Defects

TL;DR

This study uses ab initio calculations to analyze the energetics and kinetics of zigzag graphene edge reconstruction, revealing the slow initial step, defect formation, and temperature-dependent domain sizes.

Contribution

It provides new insights into the energy barriers, defect formation, and temperature effects on graphene edge reconstruction through detailed kinetic modeling.

Findings

First reconstruction step is the slowest energy barrier.

Residual defects are common when domains merge.

Average domain length decreases exponentially with temperature.

Abstract

Ab initio calculations are performed to study consecutive reconstruction of a zigzag graphene edge. According to the obtained energy profile along the reaction pathway, the first reconstruction step, formation of the first pentagon-heptagon pair, is the slowest one, while the growth of an already nucleated reconstructed edge domain should occur steadily at a much higher rate. Domains merge into one only in 1/4 of cases when they get in contact, while in the rest of the cases, residual defects are left. Structure, energy and magnetic properties of these defects are studied. It is found that spontaneous formation of pairs of residual defects (i.e. spontaneous domain nucleation) in the fully reconstructed edge is unlikely at temperatures below 1000 K. Using a kinetic model, we show that the average domain length is of several $\mathrm{\mu}$m at room temperature and it decreases exponentially upon increasing the temperature at which the reconstruction takes place.