Humidity Sensing Properties of Different Atomic Layers of Graphene on SiO2/Si Substrate

TL;DR

This study investigates how the number of atomic layers of graphene affects humidity sensor performance on SiO2/Si substrates, revealing layer-dependent responsivity and response times for potential biomedical applications.

Contribution

It is the first to systematically analyze the impact of graphene atomic layers on humidity sensing performance on SiO2/Si substrates.

Findings

Relative resistance change decreases with more graphene layers.

Tri-layer graphene sensors have the fastest response/recovery.

Double-layer graphene sensors offer a good balance of responsivity and stability.

Abstract

Graphene has the great potential to be used for humidity sensing due to ultrahigh surface area and conductivity. However, the impact of different atomic layers of graphene on SiO2/Si substrate on the humidity sensing have not been studied yet. In this paper, we fabricated three types of humidity sensors on SiO2/Si substrate based on one to three atomic layers of graphene, in which the sensing areas of graphene are 75 {\mu}m * 72 {\mu}m and 45 {\mu}m * 72 {\mu}m, respectively. We studied the impact of both the number of atomic layers of graphene and the sensing areas of graphene on the responsivity and response/recovery time of the prepared graphene-based humidity sensors. We found the relative resistance change of the prepared devices decreased with the increase of number of atomic layers of graphene under the same change of relative humidity. Further, devices based on tri-layer graphene showed the fastest response/recovery time while devices based on double-layer graphene showed the slowest response/recovery time. Finally, we chose the devices based on double-layer graphene that have relatively good responsivity and stability for application in respiration monitoring and contact-free finger monitoring.