Optical spectroscopy of interlayer coupling in artificially stacked MoS2 layers

TL;DR

This study uses optical spectroscopy to analyze how stacking angle and interlayer distance affect interlayer coupling in artificially assembled MoS2 layers, revealing energy transfer mechanisms despite electronic decoupling.

Contribution

It introduces a comprehensive optical spectroscopy approach to characterize interlayer coupling in custom-stacked MoS2 layers with varied stacking configurations.

Findings

Resonant energy transfer occurs between layers even when electronically decoupled.

Artificial stacks show similar valley polarization as monolayers at low temperatures.

Interlayer coupling varies with stacking angle and interlayer distance.

Abstract

We perform an optical spectroscopy study to investigate the properties of different artificial MoS$_2$ bi- and trilayer stacks created from individual monolayers by a deterministic transfer process. These twisted bi- and trilayers differ from the common 2H stacking in mineral MoS$_2$ in the relative stacking angle of adjacent layers and the interlayer distance. The combination of Raman spectroscopy, second-harmonic-generation microscopy and photoluminescence measurements allows us to determine the degree of interlayer coupling in our samples. We find that even for electronically decoupled artificial structures, which show the same valley polarization degree as the constituent MoS$_2$ monolayers at low temperatures, there is a resonant energy transfer between individual layers which acts as an effective luminescence quenching mechanism.