Mobility enhancement in graphene by in situ reduction of random strain fluctuations

TL;DR

This study shows that applying uniaxial strain to graphene reduces local strain fluctuations, significantly improving carrier mobility and decreasing residual doping, as confirmed by transport and Raman measurements.

Contribution

The paper demonstrates in situ reduction of strain fluctuations in graphene via uniaxial strain, leading to enhanced mobility and reduced doping, revealing strain as a key disorder source.

Findings

Mobility increased by ~35% with 0.2% uniaxial strain

Residual doping decreased by ~39% under strain

Strong correlation between mobility and doping levels

Abstract

Microscopic corrugations are ubiquitous in graphene even when placed on atomically flat substrates. These result in random local strain fluctuations limiting the carrier mobility of high quality hBN-supported graphene devices. We present transport measurements in hBN-encapsulated devices where such strain fluctuations can be in situ reduced by increasing the average uniaxial strain. When $\sim0.2\%$ of uniaxial strain is applied to the graphene, an enhancement of the carrier mobility by $\sim35\%$ is observed while the residual doping reduces by $\sim39\%$. We demonstrate a strong correlation between the mobility and the residual doping, from which we conclude that random local strain fluctuations are the dominant source of disorder limiting the mobility in these devices. Our findings are also supported by Raman spectroscopy measurements.