Resistive Graphene Humidity Sensors with Rapid and Direct Electrical Readout

TL;DR

This paper presents a rapid, direct electrical readout humidity sensor using CVD graphene on SiO2, demonstrating high sensitivity, selectivity, and fast response times, suitable for integration with CMOS circuits.

Contribution

The study introduces a graphene-based humidity sensor with rapid response and direct electrical readout, validated through experiments and density functional theory simulations.

Findings

Response and recovery times are on the order of hundreds of milliseconds.

Sensor shows selectivity towards water vapor over other gases.

Device is compatible with CMOS integration.

Abstract

We demonstrate humidity sensing using a change of electrical resistance of a single- layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N2), oxygen (O2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. Results from the interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO2 substrate, which in turn leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical read out and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.