High mobility graphene field effect transistors on flexible EVA/PET foils

Abstract

Monolayer graphene is a promising material for a wide range of applications, including sensors, optoelectronics, antennas, EMR shielding, flexible electronics, and conducting electrodes. Chemical vapor deposition (CVD) of carbon atoms on a metal catalyst is the most scalable and cost-efficient method for synthesizing high-quality, large-area monolayer graphene. The usual method of transferring the CVD graphene from the catalyst to a target substrate involves a polymer carrier which is dissolved after the transfer process is completed. Due to often unavoidable damage to graphene, as well as contamination and residues, carrier mobilities are typically 1 000 − 3 000 cm^2/(V s), unless complex and elaborate measures are taken. Here, we report on a simple scalable fabrication method for flexible graphene field-effect transistors that eliminates the polymer interim carrier, by laminating the graphene directly onto office lamination foils, removing the catalyst, and depositing Parylene N as a gate dielectric and encapsulation layer. The fabricated transistors show field and Hall-effect mobilities of 7 000 − 10 000 cm^2/(V s) with a residual charge-carrier density of 2 × 10^11 1/cm^2 at room temperature. We further validate the material quality by terahertz time domain spectroscopy (THz-TDS) and observation of the quantum Hall effect at low temperatures in a moderate magnetic field of ∼ 5 T. The Parylene encapsulation provides long-term stability and protection against additional lithography steps, enabling vertical device integration in multilayer electronics on a flexible platform.