The optical properties of transferred graphene and the dielectrics grown on it obtained by ellipsometry

TL;DR

This study uses spectroscopic ellipsometry to analyze the optical properties of transferred CVD graphene and dielectric layers grown on it, highlighting the importance of accounting for contamination and substrate effects.

Contribution

It introduces a method to accurately determine the thickness and optical properties of transferred graphene layers considering substrate effects and contamination.

Findings

Ellipsometry can accurately measure transferred graphene thickness when substrate effects are considered.

Contamination from transfer chemicals affects the optical properties of graphene.

Dielectric layers grown on graphene can be characterized optically using the proposed approach.

Abstract

Graphene layers grown by chemical vapour deposition (CVD) method and transferred from Cu-foils to the oxidized Si-substrates were investigated by spectroscopic ellipsometry (SE), Raman and X-Ray Photoelectron Spectroscopy (XPS) methods. The optical properties of transferred CVD graphene layers do not always correspond to the ones of the exfoliated graphene due to the contamination from the chemicals used in the transfer process. However, the real thickness and the mean properties of the transferred CVD graphene layers can be found using ellipsometry if a real thickness of the SiO2 layer is taken into account. The pulsed layer deposition (PLD) and atomic layer deposition (ALD) methods were used to grow dielectric layers on the transferred graphene and the obtained structures were characterized using optical methods. The approach demonstrated in this work could be useful for the characterization of various materials grown on graphene.