Analog and digital control of graphene field effect transistor sensors with the Raspberry Pi

Abstract

Graphene based sensing platforms have been used in the development of novel sensors requiring high sensitivity and discriminatory selectivity with much success in many recent research publications. This report discusses the integration, and theory of operation behind such devices, mainly commercially available platforms of graphene field effect transistors (GFET). These devices are easily controlled on a breadboard with Python run on the Raspberry Pi 4 with an Analog-to-Digital Controller (ADC) and Digital-to-Analog Controller (DAC) shield. The control circuit for GFET signal reading uses passive bypass and decoupling circuits to power a current-driven full-bridge resistance measurement across the GFET channel. Voltage values are read directly, stored, converted to resistance measures, and plotted with a Python automation script. The data collected clearly shows the channel resistance across the GFET actively controlled for signaling with a common gate architecture. The increase in channel resistance with increasing voltage bias across the gate is indicative of several phenomena: formation of p-channel depletion layer buildup, parasitic capacitance arresting electron flow, trap quantum state activations across the graphene surface, band bending of the graphene Dirac zero-points in the presence of an electric potential field, as well as shunting electron tunneling in the [0001] direction into the Si (111) wafer substrate.