Molecular Bridge Mediated Ultra-Low-Power Gas Sensing

TL;DR

This paper introduces a novel ultra-low-power gas sensor that detects target gases by measuring changes in tunneling characteristics across a molecular junction formed by gas-capturing SAMs, achieving high sensitivity and minimal power consumption.

Contribution

The study demonstrates a new molecular junction-based gas sensing device that significantly reduces power consumption and enhances sensitivity through gas-mediated tunneling mechanisms.

Findings

Over 10^8 times resistance change upon gas exposure

Ultra-low standby power consumption below 15 pW

Effective detection of 80 ppm diamine gas

Abstract

We report the electrical detection of captured gases through measurement of the tunneling characteristics of gas-mediated molecular junctions formed across nanogaps. The gas sensing nanogap device consists of a pair of vertically stacked gold electrodes separated by an insulating spacer of (~1.5 nm of sputtered amorphous Si and ~4.5 nm ALD SiO2) which is notched ~10 nm along the edges of the top electrode. The exposed gold surface is functionalized with a self-assembled monolayer (SAM) of conjugated thiol linker molecules. When the device is exposed to a target gas (1, 5-diaminopentane), the SAM layer electrostatically captures the target gas molecules forming a molecular bridge across the nanogap. The gas capture lowers the barrier potential for electron tunneling from ~5 eV to ~0.9 eV across the notched edge regions and establishes additional conducting paths for charge transport between the gold electrodes, leading to a substantial decrease in junction resistance. We demonstrated an output resistance change of greater than 100000000 times on exposure to 80 ppm of diamine target gas as well as ultra-low standby power consumption of smaller than 15 pW, confirming electron tunneling through molecular bridges for ultra-low power gas sensing.