Biaxial Tensile Strain Enhances Electron Mobility of Monolayer Transition Metal Dichalcogenides

TL;DR

Applying biaxial tensile strain to monolayer WS$_2$ and MoS$_2$ significantly enhances electron mobility, achieving the highest reported improvements at low strain levels, through reduced intervalley electron-phonon scattering.

Contribution

This study demonstrates for the first time that biaxial tensile strain can substantially improve electron mobility in monolayer 2D semiconductors, supported by experimental and theoretical analysis.

Findings

~2x higher on-state current and mobility at 0.3% strain in WS$_2$

Enhanced mobility primarily due to reduced intervalley electron-phonon scattering

Highest mobility improvement at the lowest strain reported to date

Abstract

Strain engineering can modulate the material properties of two-dimensional (2D) semiconductors for electronic and optoelectronic applications. Recent theory and experiments have found that uniaxial tensile strain can improve the electron mobility of monolayer MoS$_2$, a 2D semiconductor, but the effects of biaxial strain on charge transport are not well-understood in 2D semiconductors. Here, we use biaxial tensile strain on flexible substrates to probe the electron mobility in monolayer WS$_2$ and MoS$_2$ transistors. This approach experimentally achieves ~2x higher on-state current and mobility with ~0.3% applied biaxial strain in WS$_2$, the highest mobility improvement at the lowest strain reported to date. We also examine the mechanisms behind this improvement through density functional theory simulations, concluding that the enhancement is primarily due to reduced intervalley electron-phonon scattering. These results underscore the role of strain engineering 2D semiconductors for flexible electronics, sensors, integrated circuits, and other optoelectronic applications.