Raman Spectral Indicators of Catalyst Decoupling for Transfer of CVD Grown 2D Materials

TL;DR

This paper demonstrates a scalable Raman spectroscopy method to predict and improve the transfer quality of 2D materials like graphene and h-BN from copper catalysts, achieving near-perfect coverage on large wafers.

Contribution

It introduces a Raman spectral indicator for catalyst decoupling that enables high-yield, wafer-scale transfer of 2D materials with real-time monitoring capabilities.

Findings

Strong correlation between Raman 2D peak features and transfer success

Achieved over 97.5% monolayer coverage for h-BN and 99.7% for graphene

Process is scalable and compatible with roll-to-roll manufacturing

Abstract

Through a combination of monitoring the Raman spectral characteristics of 2D materials grown on copper catalyst layers, and wafer scale automated detection of the fraction of transferred material, we reproducibly achieve transfers with over 97.5% monolayer hexagonal boron nitride and 99.7% monolayer graphene coverage, for up to 300 mm diameter wafers. We find a strong correlation between the transfer coverage obtained for graphene and the emergence of a lower wavenumber 2D- peak component, with the concurrent disappearance of the higher wavenumber 2D+ peak component during oxidation of the catalyst surface. The 2D peak characteristics can therefore act as an unambiguous predictor of the success of the transfer. The combined monitoring and transfer process presented here is highly scalable and amenable for roll-to-roll processing.