Investigation of the dynamic bending properties of MoS2 thin films by interference colours.

Peng Wang,Han Huang,Xiaohong Li,Shubo Cheng,Si Xiao,Jun He,Bosai Lyu,Yongli Gao,Yingbao Huang

doi:10.1038/srep18441

Abstract

A non-contact method for the observation of the elastic deformation of 2D molybdenum disulfide (MoS2) thin films using an ordinary optical microscope is reported. A pulsed laser is used to rapidly increase the bending deformation of the MoS2 thin films via heating. The bending angle of the MoS2 thin films shows high stability, changing only 5% in forty days without external forces. However, the bending angle of the MoS2 thin films substantially decreases after being wetted with the volatile polar solvent tetrahydrofuran (THF), because of its low surface tension. By removing the nano-Newton scale forces on the MoS2 thin films, the bending angle increases significantly within 4 minutes, and this feature of the thin films shows great potential for use in the fabrication of micro-force sensors. This is the first attempt to study the mechanical properties of 2D materials by optical methods. Further utilization of industrially manufactured MoS2 thin films for detecting micro-force qualitatively on the basis of their excellent bending properties would significantly reduce the production costs of micro-force sensors.

Highlights

Films are measured, and the error determined by AFM is less than 2%
Our findings show that micro-forces can be characterized qualitatively on the basis of the elastic bending of commercial MoS2 thin films, which would reduce the cost of micro-elastic dynamometers
The isoclinic interference is determined by the distances from the upper surface and lower surface of the MoS2 thin films, which can be clearly observed if the thickness of MoS2 thin films exceeds 250 nm according to the optical theory[21]

Summary

Introduction

Films are measured, and the error determined by AFM is less than 2%. Modulations are consistent with the experimental results showing that the gap variation leads to the changes in the interference colours. We measured the nano-Newton forces on the basis of the elastic property of the MoS2 thin films directly with a simple optical instrument. Our findings show that micro-forces can be characterized qualitatively on the basis of the elastic bending of commercial MoS2 thin films, which would reduce the cost of micro-elastic dynamometers

Methods

Results

Conclusion