Spectroscopic Evaluation of Charge-transfer Doping and Strain in Graphene/MoS2 Heterostructures

TL;DR

This study uses Raman and photoluminescence spectroscopy to analyze how mechanical exfoliation and thermal annealing affect strain and charge transfer in graphene/MoS2 heterostructures, revealing tunable electromechanical properties.

Contribution

It introduces a spectroscopic method to simultaneously evaluate and modulate strain and charge transfer in 2D heterostructures.

Findings

Both layers experience compressive strain and doping after fabrication.

Thermal annealing modulates strain and carrier concentration.

The study emphasizes the importance of mechanical and electronic coupling in heterostructures.

Abstract

It is important to study the van der Waals interface in emerging vertical heterostructures based on layered two-dimensional (2D) materials. Being atomically thin, 2D materials are susceptible to significant strains as well as charge transfer doping across the interfaces. Here we use Raman and photoluminescence (PL) spectroscopy to study the interface between monolayer graphene/MoS2 heterostructures prepared by mechanical exfoliation and layer-by-layer transfer. By using correlation analysis between the Raman modes of graphene and MoS2 we show that both layers are subjected to compressive strain and charge transfer doping following mechanical exfoliation and thermal annealing. Furthermore, we show that both strain and carrier concentration can be modulated in the heterostructures with additional thermal annealing. Our study highlights the importance of considering both mechanical and electronic coupling when characterizing the interface in van der Waals heterostructures, and demonstrates a method to tune their electromechanical properties.