STUDY ON 2D GRAPHENE AS THE SENSING FILM OF ISFETS FOR PH SENSING APPLICATIONS

Abstract

This work aims to investigate the sensing performances of CVD graphene, develop highly stable graphene-based ISFETs with reduced drift and hysteresis effects and further improve the sensing performance by applying plasma treatments on graphene. The advantage of graphene is its robust honeycomb ring structure formed by tightly bonded sp² carbons, which makes it a super barrier against diffusion species like water. This property addresses the stability issues of ISFETs, which are mainly caused by the slow penetration of water and water-related species into the gate oxide. As a result, graphene-based ISFETs exhibit low drift rates below 1 mV/hr, and small hysteresis widths within 3.4 mV. Meanwhile, the sensitivity can be tuned by surface plasma treatments like O₂, reaching up to 40 mV/pH. The final demonstration of a reference-less ISFET shows a drift rate as low as 0.38mV/hr, indicating the unlimited potentials for future graphene-based ISFETs.