Intrinsic Response of Graphene Vapor Sensors

TLDR

Graphene’s exceptional chemical sensor properties are well known, but the effect of lithography‑residue contamination on sensor performance remains unclear. The authors developed a cleaning protocol that removes resist residue, enabling measurement of graphene’s intrinsic chemical response. Contamination layers chemically dope graphene, increase scattering, and concentrate analytes, boosting sensor response, yet the intrinsic graphene response to strong vapors like ammonia is unexpectedly weak.

Abstract

Graphene is a two-dimensional material with extremely favorable chemical sensor properties. Conventional nanolithography typically leaves a resist residue on the graphene surface, whose impact on the sensor characteristics has not yet been determined. Here we show that the contamination layer chemically dopes the graphene, enhances carrier scattering, and acts as an absorbent layer that concentrates analyte molecules at the graphene surface, thereby enhancing the sensor response. We demonstrate a cleaning process that verifiably removes the contamination on the device structure and allows the intrinsic chemical responses of the graphene monolayer to be measured. These intrinsic responses are surprisingly small, even upon exposure to strong analytes such as ammonia vapor.