A Gas Sensor Based on a Single SnO Micro-Disk

Mateus Masteghin,Marcelo Orlandi

doi:10.3390/s18103229

Abstract

In this study, individual nanofabricated SnO micro-disks, previously shown to exhibit exceptional sensitivity to NOx, are investigated to further our understanding of gas sensing mechanisms. The SnO disks presenting different areas and thickness were isolated and electrically connected to metallic electrodes aided by a Dual Beam Microscope (SEM/FIB). While single micro-disk devices were found to exhibit short response and recovery times and low power consumption, large interconnected arrays of micro-disks exhibit much higher sensitivity and selectivity. The source of these differences is discussed based on the gas/solid interaction and transport mechanisms, which showed that thickness plays a major role during the gas sensing of single-devices. The calculated Debye length of the SnO disk in presence of NO2 is reported for the first time.

Highlights

Large-scale combustion of fossil fuels, while well known to contribute to global warming and air pollution, is likely to continue for many decades to satisfy the continued growth in worldwide demands for electrical power, heating and cooling, and high energy density fuels for vehicles
The key byproducts of fossil fuel combustion include gases such as CO and hydrocarbons due to incomplete combustion, NO2 that arises from the reaction of atmospheric N2 and O2 gases at the high temperatures and pressures experienced under combustion, as well as CO2 and water vapor
A suspension containing SnO disks was prepared in isopropyl alcohol, dispersed in an ultrasonic bath, and one drop was deposited onto Si/SiO2 substrates with interdigitated platinum electrodes (IDE)

Summary

Introduction

Large-scale combustion of fossil fuels, while well known to contribute to global warming and air pollution, is likely to continue for many decades to satisfy the continued growth in worldwide demands for electrical power, heating and cooling, and high energy density fuels for vehicles. Considerable progress has been made over the past decades in minimizing such emissions by the introduction of various emission sensors (e.g., zirconia-based electrochemical oxygen sensors) [2,3], catalysts (e.g., three-way catalysts) [4] and traps (e.g., lean NOx traps) [5]. Semiconducting metal oxide (SMO) nanowire-based structures are some of the most studied chemoresistive devices, in which gases adsorbed/chemisorbed on the surface of such materials modulate their conductivity. In terms of SMOs applied for chemoresistive devices, by far the greatest attention has been focused on tin dioxide (SnO2 ), given its robust character and proven sensitivity to many types of gases [7,8]. Other stoichiometries in the Sn-O system have been identified as having exceptional sensor characteristics, including the Sn3 O4 [9,10,11] and SnO [12]

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