Two-dimensional Graphene Heterojunctions: the Tunable Mechanical Properties

TL;DR

This study investigates the mechanical properties of two-dimensional graphene heterojunctions with various allotropes, revealing how composition and structure influence their brittleness, hardening behavior, and potential for flexible electronic applications.

Contribution

It provides a comprehensive analysis of the tensile behavior of graphene heterojunctions, highlighting the effects of different allotropes and configurations on their mechanical properties.

Findings

All heterojunctions are brittle except alpha-GY, which hardens due to triple carbon rings.

Yielding initiates at the interface between graphene and allotropes, with monoatomic rings forming afterward.

Increasing graphene percentage decreases yield strain and increases Young's modulus.

Abstract

We report the mechanical properties of different two-dimensional carbon heterojunctions (HJs) made from graphene and various stable graphene allotropes, including {\alpha}-, {\beta}-, {\gamma}- and 6612-graphyne (GY), and graphdiyne (GDY). It is found that all HJs exhibit a brittle behaviour except the one with {\alpha}-GY, which however shows a hardening process due to the formation of triple carbon rings. Such hardening process has greatly deferred the failure of the structure. The yielding of the HJs is usually initiated at the interface between graphene and graphene allotropes, and monoatomic carbon rings are normally formed after yielding. By varying the locations of graphene (either in the middle or at the two ends of the HJs), similar mechanical properties have been obtained, suggesting insignificant impacts from location of graphene allotropes. Whereas, changing the types and percentages of the graphene allotropes, the HJs exhibit vastly different mechanical properties. In general, with the increasing graphene percentage, the yield strain decreases and the effective Young's modulus increases. Meanwhile, the yield stress appears irrelevant with the graphene percentage. This study provides a fundamental understanding of the tensile properties of the heterojunctions that are crucial for the design and engineering of their mechanical properties, in order to facilitate their emerging future applications in nanoscale devices, such as flexible/stretchable electronics.