Impact of Mismatch Angle on Electronic Transport Across Grain Boundaries and Interfaces in 2D Materials

Arnab K. Majee,Cameron J. Foss,Zlatan Aksamija

doi:10.1038/s41598-017-16744-0

Arnab K. Majee, Cameron J. Foss + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-16744-0

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Abstract

We study the impact of grain boundaries (GB) and misorientation angles between grains on electronic transport in 2-dimensional materials. Here we have developed a numerical model based on the first-principles electronic bandstructure calculations in conjunction with a method which computes electron transmission coefficients from simultaneous conservation of energy and momentum at the interface to essentially evaluate GB/interface resistance in a Landauer formalism. We find that the resistance across graphene GBs vary over a wide range depending on misorientation angles and type of GBs, starting from 53 Ω μm for low-mismatch angles in twin (symmetric) GBs to about 1020 Ω μm for 21° mismatch in tilt (asymmetric) GBs. On the other hand, misorientation angles have weak influence on the resistance across MoS2 GBs, ranging from about 130 Ω μm for low mismatch angles to about 6000 Ω μm for 21°. The interface resistance across graphene-MoS2 heterojunctions also exhibits a strong dependence on misorientation angles with resistance values ranging from about 100 Ω μm for low-mismatch angles in Class-I (symmetric) interfaces to 1015 Ω μm for 14° mismatch in Class-II (asymmetric) interfaces. Overall, symmetric homo/heterojunctions exhibit a weak dependence on misorientation angles, while in MoS2 both symmetric and asymmetric GBs show a gradual dependence on mismatch angles.

Highlights

Besides experimental measurements, there are several theoretical studies[15,16,17,18,19] which have helped to gain more insight on transport across graphene grain boundaries (GB)
To study the impact of misorientation angles on interface resistance, we have developed a numerical model based on first-principles Density Functional Theory (DFT) electronic bandstructure calculations and electron transmission coefficients from simultaneous energy and momentum conservation
We calculate the transmission and resistance of graphene GBs in order to explore the impact of the misorientation angle

Summary

Introduction

There are several theoretical studies[15,16,17,18,19] which have helped to gain more insight on transport across graphene GBs. Graphene has been reported to form an ohmic contact with MoS226,37, resulting in an increase in mobility up to an order of magnitude as compared to that of in metal-MoS2 field-effect transistors (FETs) This calls for investigating the role of misorientation angles in determining the graphene-MoS2 interface resistance in such heterostructures. To study the impact of misorientation angles on interface resistance, we have developed a numerical model based on first-principles DFT electronic bandstructure calculations and electron transmission coefficients from simultaneous energy and momentum conservation. The latter is an extension of the approach originally proposed by Yazyev and Louie[15] to calculate the transmission coefficient of electrons across a graphene grain boundary

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