Ultra-clean high-mobility graphene on technologically relevant substrates

Abstract

Graphene grown via chemical vapour deposition (CVD) on copper foil has emerged as a high-quality, scalable material, that can be easily integrated on technologically relevant platforms to develop promising applications in the fields of optoelectronics and photonics. Most of these applications require low-contaminated high-mobility graphene (i.e., approaching 10 000 cm² V⁻¹ s⁻¹ at room temperature) to reduce device losses and implement compact device design. To date, these mobility values are only obtained when suspending or encapsulating graphene. Here, we demonstrate a rapid, facile, and scalable cleaning process, that yields high-mobility graphene directly on the most common technologically relevant substrate: silicon dioxide on silicon (SiO₂/Si). Atomic force microscopy (AFM) and spatially-resolved X-ray photoelectron spectroscopy (XPS) demonstrate that this approach is instrumental to rapidly eliminate most of the polymeric residues which remain on graphene after transfer and fabrication and that have adverse effects on its electrical properties. Raman measurements show a significant reduction of graphene doping and strain. Transport measurements of 50 Hall bars (HBs) yield hole mobility μ_h up to ∼9000 cm² V⁻¹ s⁻¹ and electron mobility μ_e up to ∼8000 cm² V⁻¹ s⁻¹, with average values μ_h ∼ 7500 cm² V⁻¹ s⁻¹ and μ_e ∼ 6300 cm² V⁻¹ s⁻¹. The carrier mobility of ultraclean graphene reaches values nearly double than those measured in graphene processed with acetone cleaning, which is the method widely adopted in the field. Notably, these mobility values are obtained over large-scale and without encapsulation, thus paving the way to the adoption of graphene in optoelectronics and photonics.