Resistive humidity sensor made from palm-oil-derived graphene film

Abstract

Graphene is known to be highly conductive and sensitive to adsorbed molecules thus make it suitable for sensor application. The astonishing properties of graphene attracted the attention to develop ultra-high sensitive sensor with very fast response and recovery time. In this project, a resistive humidity sensor which utilizes graphene as the sensing area has been fabricated and characterized. Different types of graphene samples (i.e. single-layer graphene on copper substrate, single-layer graphene on nickel substrate synthesized using thermal CVD, multi-layers graphene on nickel substrate synthesized using thermal CVD) were used in this project to further investigate the effect of crystallinity of the graphene on its sensing behavior. In order to fabricate the sensor device, the 2-terminals and 4-terminals electrodes configuration was chosen. Sensor fabrication process includes photolithography, copper etching and graphene transfer process. Current-voltage measurement of the fabricated is performed at different relative humidity inside dry box. The result of the resistance of the graphene sample responding towards the change of relative humidity shows an inverse exponential association. Measurement result for different type of graphene are compared to assess the relationship between the crystallinity and sensor performance.