Low-Humidity Sensing Properties of Multi-Layered Graphene Grown by Chemical Vapor Deposition

Abstract

Humidity sensing is fundamental in some applications, as humidity can be a strong interferent in the detection of analytes under environmental conditions. Ideally, materials sensitive or insensitive towards humidity are strongly needed for the sensors used in the first or second case, respectively. We present here the sensing properties of multi-layered graphene (MLG) upon exposure to different levels of relative humidity. We synthesize MLG by chemical vapor deposition, as shown by Raman spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Through an MLG-based resistor, we show that MLG is scarcely sensitive to humidity in the range 30%–70%, determining current variations in the range of 0.005%/%relative humidity (RH) well below the variation induced by other analytes. These findings, due to the morphological properties of MLG, suggest that defective MLG is the ideal sensing material to implement in gas sensors operating both at room temperature and humid conditions.

Humidity sensor based on multi-layer graphene (MLG) integrated onto a micro-hotplate (MHP)

“…A previous report working with MLG synthesized at similar conditions [11] shows a low-humidity response of the MLG-based device. But in that case, the SiO2 is the dielectric layer used to insulate the MLG from the Si wafer.…”

Reduced Graphene Oxide/Polyelectrolyte Multilayers for Fast Resistive Humidity Sensing

“…In particular, materials based on graphene, an atomically thin, highly electrically conductive material with ultrahigh specific surface area [ 43 , 44 ], have shown great potential for humidity sensing [ 22 , 23 , 45 ]. However, pristine graphene exhibits poor sensitivity towards humidity due to its lack of reactive sites for interacting with polar water molecules [ 46 ]. To address this issue, graphene oxide (GO) has been investigated for its surficial oxygen-containing functional groups, such as hydroxyl, carboxyl, and epoxy groups, which enable it to interact with water molecules [ 9 , 47 , 48 ].…”