Mechanistic insight into the limiting factors of graphene-based environmental sensors

TL;DR

This study investigates how microscopic surface imperfections and cleanliness influence the performance of graphene-based environmental sensors, using experimental and theoretical methods to identify key limiting factors.

Contribution

It provides new insights into the microscopic interactions affecting graphene sensor performance and highlights the importance of surface cleanliness for device reliability.

Findings

Surface cleanliness critically impacts sensor performance.

Thermal treatments and surface visualization correlate with sensing efficiency.

Contaminants become more influential as sensor active zones shrink.

Abstract

Graphene has demonstrated great promise for technological use, yet control over material growth and understanding of how material imperfections affect the performance of devices are challenges that hamper the development of applications. In this work we reveal new insight into the connections between the performance of the graphene devices as environmental sensors and the microscopic details of the interactions at the sensing surface. Specifically, we monitor changes in the resistance of the chemical-vapour deposition grown graphene devices as exposed to different concentrations of ethanol. We perform thermal surface treatments after the devices are fabricated, use scanning probe microscopy to visualize their effects on the graphene sensing surface down to nanometer scale and correlate them with the measured performance of the device as an ethanol sensor. Our observations are compared to theoretical calculations of charge transfers between molecules and the graphene surface. We find that, although often overlooked, the surface cleanliness after device fabrication is responsible for the device performance and reliability. These results further our understanding of the mechanisms of sensing in graphene-based environmental sensors and pave the way to optimizing such devices, especially for their miniaturization, as with decreasing size of the active zone the potential role of contaminants will rise.