In-situ Raman Spectroscopy of the Graphene / Water Interface of a Solution-Gated Field Effect Transistor: Electron-Phonon Coupling and Spectroelectrochemistry

TL;DR

This paper introduces a combined electrical and Raman spectroscopic method to study the graphene/water interface in solution-gated transistors, revealing electron-phonon interactions and electrochemical reactions in real-time.

Contribution

It presents a novel in-situ measurement technique integrating Raman spectroscopy with electrical characterization of graphene transistors, enabling detailed analysis of electrochemical processes.

Findings

Raman signatures linked to electron-phonon coupling were observed.

Capacitance and Fermi levels of bilayer graphene were accurately determined.

Electrochemical reactions were monitored in-situ, showing partial reversibility.

Abstract

We present a novel measurement approach which combines the electrical characterization of solution-gated field effect transistors based on epitaxial bilayer graphene on 4H-SiC (0001) with simultaneous Raman spectroscopy. By changing the gate voltage, we observed Raman signatures related to the resonant electron-phonon coupling. An analysis of these Raman bands enabled the extraction of the geometrical capacitance of the system and an accurate calculation of the Fermi levels for bilayer graphene. An intentional application of higher gate voltages allowed us to trigger electrochemical reactions, which we followed in-situ by Raman spectroscopy. The reactions showed a partially reversible character, as indicated by an emergence / disappearance of peaks assigned to C-H and Si-H vibration modes as well as an increase / decrease of the defect-related Raman D band intensity. Our setup provides a highly interesting platform for future spectroelectrochemical research on electrically induced sorption processes of graphene on the micrometer scale.