Quantitative Raman spectrum and reliable thickness identification for atomic layers on insulating substrates

Area of Science:

• Materials Science
• Spectroscopy
• Nanotechnology

Background:

• Quantifying Raman intensities in stacked layers is challenging.
• Accurate thickness determination of atomic layers is crucial for material characterization.
• Existing methods may lack speed or precision for atomic-scale layers.

Purpose of the Study:

• To propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates.
• To quantify Raman intensities of both specimen and substrate layers in a stacked configuration.
• To compare wide-range Raman data of atomically flat MoS2 flakes with theoretical models.

Main Methods:

• Collecting wide-range Raman spectroscopy data for atomically flat MoS2 flakes.
• Incorporating optical interference effects into theoretical models.
• Analyzing specimen and substrate spectral intensities.
• Developing a substrate-weighted spectral intensity metric.

Main Results:

• Raman intensity features were accurately captured by including optical interference.
• Freely suspended few-layer chalcogenide flakes showed a stronger Raman response than bulk.
• Specimen spectrum intensity oscillated with thickness, but substrate-weighted intensity became monotonic.
• The substrate-weighted spectral intensity demonstrated sensitivity to specimen thickness.

Conclusions:

• A general and rapid thickness identification technique for atomic layers on dielectric substrates was demonstrated.
• The substrate-weighted spectral intensity is a reliable metric for accurate atomic layer thickness determination.
• This method offers a significant advancement in characterizing 2D materials.