Piezoresistivity and Strain-induced Band Gap Tuning in Atomically Thin MoS2

TL;DR

This study demonstrates strain-tunable bandgap modulation and piezoresistive effects in atomically thin MoS2 layers, highlighting its potential for advanced nanoelectromechanical systems and flexible electronics.

Contribution

It provides experimental evidence and finite element simulations of strain-induced bandgap tuning and piezoresistivity in monolayer, bilayer, and trilayer MoS2, with high gauge factors.

Findings

Piezoresistive gauge factors of -148, -224, and -43.5 for monolayer, bilayer, and trilayer MoS2.

Strain induces significant bandgap changes detectable via electrical conductivity.

MoS2's piezoresistive response surpasses that of suspended graphene, making it promising for NEMS applications.

Abstract

The bandgap of MoS2 is highly strain-tunable which results in the modulation of its electrical conductivity and manifests itself as the piezoresistive effect while a piezoelectric effect was also observed in odd-layered MoS2 with broken inversion symmetry. This coupling between electrical and mechanical properties makes MoS2 a very promising material for nanoelectromechanical systems (NEMS). Here we incorporate monolayer, bilayer and trilayer MoS2 in a nanoelectromechanical membrane configuration. We detect strain-induced band gap tuning via electrical conductivity measurements and demonstrate the emergence of the piezoresistive effect in MoS2. Finite element method (FEM) simulations are used to quantify the band gap change and to obtain a comprehensive picture of the spatially varying bandgap profile on the membrane. The piezoresistive gauge factor is calculated to be -148 +/- 19, -224 +/- 19 and -43.5 +/- 11 for monolayer, bilayer and trilayer MoS2 respectively which is comparable to state-of-the-art silicon strain sensors and two orders of magnitude higher than in strain sensors based on suspended graphene. Controllable modulation of resistivity in 2D nanomaterials using strain-induced bandgap tuning offers a novel approach for implementing an important class of NEMS transducers, flexible and wearable electronics, tuneable photovoltaics and photodetection.