Role of Strain in Quantum-Confined States of Heterobilayers of 2D Materials*

In a recent report [1], the present authors demonstrated the existence of quantum-confined states arising from spatially varying band edge energies in a MoS₂/WSe₂ vertical heterostructure. Here, this system is studied in more detail, combining results from low-temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements and density functional theory (DFT) calculations. It is experimentally observed that in addition to the band edge shifts, the moiré pattern, which forms due to a 3.7% lattice mismatch, results in spatially varying biaxial strain in the MoS₂ of ~2% tension (compression) at the corrugation minima (maxima). Including band edge shifts due to strain and corrugation of the underlying WSe₂ leads to a consistent explanation for the observed spatial locations of the quantum-confined states.
[1] Y. Pan, S. Fölsch, Y. Nie, D. Waters, Y.-C. Lin, B. Jariwala, K. Zhang, K. Cho, J. A. Robinson, and R. M. Feenstra, Nano Lett. 18, 1849 (2018).