A Versatile Approach to Create Nanobubbles on Arbitrary Two‐Dimensional Materials for Imaging Exciton Localization

Abstract

Strained 2D materials with lattice deformation have the optimal band structure, lattice vibration, and thermal conductivity and various methods have been proposed to introduce strain into 2D materials. However, the creation of localized strain in arbitrary 2D materials in predesigned areas is difficult and challenging. Herein, a versatile approach to creating on‐demand nanobubbles on five different 2D materials using a functional atomic force microscopy (AFM) tip is described. Strain‐induced redshifts are observed from the Raman scattering and photoluminescence (PL) spectra of the 2D materials in the region with the nanobubble arrays. In addition, the localized exciton state is observed from the periphery of a steep WS2 nanobubble by high‐resolution nano‐photoluminescence and is supported by theoretical simulation. These results demonstrate a programmable and reliable method to create localized strain in different 2D materials and pave the way for nanoscale strain engineering of 2D materials to cater to different applications.

Enhanced Electromechanical Response Due to Inhomogeneous Strain in Monolayer MoS2

“…The halo-like phenomenon presented here coincides with a growing body of evidence for localized strain effects occurring at the periphery of nanobubbles in 2D materials. Chen et al observed a “doughnut-like” pattern in nanophotoluminescence maps of exciton emission in WS 2 nanobubbles, which they attribute to localized inhomogeneous elastic strain and the associated carrier funneling effect . Using valence force field simulations and tight-binding electronic-state calculations, Carmesin et al modeled the spatial distributions of strain and electronic states in TMD nanobubbles.…”

“…Chen et al observed a "doughnut-like" pattern in nanophotoluminescence maps of exciton emission in WS 2 nanobubbles, which they attribute to localized inhomogeneous elastic strain and the associated carrier funneling effect. 45 Using valence force field simulations and tight-binding electronic-state calculations, Carmesin et al modeled the spatial distributions of strain and electronic states in TMD nanobubbles. They showed that bubbles in monolayer MoS 2 should exhibit strong carrier localization in their peripheries due primarily to nonuniform strain and the corresponding bond deformations, which alter the bandgap and confinement potentials.…”