Line defects in Graphene: How doping affects the electronic and mechanical properties

TL;DR

This paper investigates how doping influences the electronic and mechanical properties of line defects in graphene, revealing that n-type doping and nitrogen substitution can significantly enhance tensile strength and enable tunable electronic transitions.

Contribution

The study provides a detailed first-principles analysis of doping effects on line defects in graphene, proposing doping as a strategy to strengthen and tune the material's electronic properties.

Findings

N-type doping increases tensile strength.

Nitrogen substitution stabilizes defects.

Doping enables tunable metal/semiconductor transitions.

Abstract

Graphene and carbon nanotubes have extraordinary mechanical and electronic properties. Intrinsic line defects such as local non-hexagonal reconstructions or grain boundaries, however, significantly reduce the tensile strength, but feature exciting electronic properties. Here, we address the properties of line defects in graphene from first-principles on the level of full-potential density-functional theory, and assess doping as one strategy to strengthen such materials. We carefully disentangle the global and local effect of doping by comparing results from the virtual crystal approximation with those from local substitution of chemical species, in order to gain a detailed understanding of the breaking and stabilization mechanisms. We find that n-type doping or local substitution with nitrogen increases the ultimate tensile strength significantly. In particular, it can stabilize the defects beyond the ultimate tensile strength of the pristine material. We therefore propose this as a key strategy to strengthen graphenic materials. Furthermore, we find that doping and/or applying external stress lead to tunable and technologically interesting metal/semi-conductor transitions.