Quantitative Raman Spectrum and Reliable Thickness Identification for Atomic Layers on Insulating Substrates

TL;DR

This paper introduces a rapid, reliable Raman spectroscopy method for determining the thickness of atomic layers on insulating substrates by analyzing interference effects and substrate-weighted intensities, validated on MoS2 flakes.

Contribution

It presents a novel quantitative Raman analysis technique that accurately identifies atomic layer thicknesses on dielectric substrates, incorporating optical interference effects.

Findings

Raman intensities can be quantitatively modeled including interference effects.

Substrate-weighted spectral intensity provides a monotonic and sensitive measure of thickness.

Freely suspended chalcogenide flakes exhibit stronger Raman response than bulk materials.

Abstract

We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS2 flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.