Ultra-large polymer-free suspended graphene films

TL;DR

This paper presents a novel polymer-free method to produce large, clean, suspended graphene films with uniform properties, suitable for advanced applications like ion-electron conversion, avoiding contamination issues of traditional methods.

Contribution

It introduces a polymer-free fabrication process for large suspended graphene films, maintaining high quality and uniformity, and demonstrates their practical use in mass spectrometry.

Findings

High fabrication yield of uniform triple-layer graphene films.

Structural and electronic properties similar to monolayer graphene.

Effective as thin, robust ion-electron converters in mass spectrometry.

Abstract

Due to its extraordinary properties, suspended graphene is a critical element in a wide range of applications. Preparation methods that preserve the unique properties of graphene are therefore in high demand. To date, all protocols for the production of large graphene films have relied on the application of a polymer film to stabilize graphene during the transfer process. However, this inevitably introduces contaminations that have proven to be extremely difficult, if not impossible, to remove entirely. Here we report the polymer-free fabrication of suspended films consisting of three graphene layers spanning circular holes of 150 $\mu$m diameter. We find a high fabrication yield, very uniform properties of the freestanding graphene across all holes as well across individual holes. A detailed analysis by confocal Raman and THz spectroscopy reveals that the triple-layer samples exhibit structural and electronic properties similar to those of monolayer graphene. We demonstrate their usability as ion-electron converters in time-of-flight mass spectrometry and related applications. They are two orders of magnitude thinner than previous carbon foils typically used in these types of experiments, while still being robust and exhibiting a sufficiently high electron yield. These results are an important step towards replacing free-standing ultra-thin carbon films or graphene from polymer-based transfers with much better defined and clean graphene.