Humidity Sensing in Graphene-Trenched Silicon Junctions via Schottky Barrier Modulation

TL;DR

This paper introduces a new graphene-based sensor that detects humidity by changing the electrical properties of a silicon junction.

Contribution

The novel use of suspended and supported graphene regions in a silicon junction to modulate the Schottky barrier for humidity sensing.

Findings

Humidity affects the Schottky barrier height, ideality factor, and series resistance in the sensor.

Larger trench widths reduce graphene's density of states, influencing sensor performance.

The sensor works under both forward and reverse bias with high selectivity and low power consumption.

Abstract

In this study, we develop a graphene-trenched silicon Schottky junction for humidity sensing. This novel structure comprises suspended graphene bridging etched trenches on a silicon substrate, creating both free-standing and substrate-contacting regions of graphene that enhance water adsorption sensing. Suspended graphene is intrinsically insensitive to water adsorption, making it difficult for adsorbed H2O to effectively dope the graphene. In contrast, when graphene is supported on the silicon substrate, water molecules can effectively dope the graphene by modifying the silicon’s impurity bands and their hybridization with graphene. This humidity-induced doping leads to a significant modulation of the Schottky barrier at the graphene–silicon interface, which serves as the core sensing mechanism. We investigate the current–voltage (I–V) characteristics of these devices as a function of trench width and relative humidity. Our analysis shows that humidity influences key device parameters, including the Schottky barrier height, ideality factor, series resistance, and normalized sensitivity. Specifically, larger trench widths reduce the graphene density of states, an effect that is accounted for in our analysis of these parameters. The sensor operates under both forward and reverse bias, enabling tunable sensitivity, high selectivity, and low power consumption. These features make it promising for applications in industrial and home safety, environmental monitoring, and process control.

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