Atomic Layer Deposition to Materials for Gas Sensing Applications

Abstract

Atomic layer deposition is a thin film deposition technique based on self‐terminated surface reactions. Contrarily to most of the thin film deposition techniques, it is not a line of sight deposition technique due to the sequential introduction of the gaseous precursors and because the reactants can only react with surface species. The precursors can thus diffuse into porous structures and the conformal coating of high aspect ratio structures can be achieved. Because of these peculiarities, atomic layer deposition is an attractive technique for fabricating materials to be applied in resistive gas sensors. This article focuses on materials for resistive gas sensor devices in which the sensing material is elaborated using atomic layer deposition, in at least one step of the fabrication. It will be shown that atomic layer deposition has proven to be well‐suited for the elaboration of compact thin films, nanostructures, and heterostructures to be applied for the detection of a variety of analytes such as toxic compounds, pollutants, explosives, etc. The chemical and physical properties of the sensing layers will be discussed in parallel to the gas sensing mechanisms in an attempt to develop clear structure–property correlations

The Effect of Film Thickness on the Gas Sensing Properties of Ultra-Thin TiO2 Films Deposited by Atomic Layer Deposition

“…Previously, reported methods for depositing thin film gas sensing materials include magnetron sputtering [5], sol-gel [6], chemical vapor deposition (CVD) [7], ultrasonic spray pyrolysis [5] and more recently by atomic layer deposition (ALD) [8]. ALD is a gas-phase thin film deposition technique that involves sequential, alternative dosing of chemical precursors.…”

“…ALD allows atomic level control of film growth, allowing fabrication of materials with defined thickness and is capable of depositing semiconductor materials in the order of the Debye length, making it an ideal tool for exploring the fundamental sensing properties of these materials. The use of ALD for deposition of gas sensing materials has recently been reviewed [8] but the most persuasive demonstration of the use of ALD for exploring the thickness dependence of sensor response has been the work of Du and George for SnO 2 [3] where an optimum sensitivity was found at a film thickness of 3 nm, which was suggested to correlate with the Debye length of the material under the test conditions.…”

Semiconducting Metal Oxides Nanocomposites for Enhanced Detection of Explosive Vapors

“…), surface potential and intercrystallite barriers, phase composition, sizes of crystallites, and others also [33,34]. Heterojunctions can increase SMOs' sensitivity and are based on two different metal oxides admixed or layered together (p-n, n-n and p-p diodes made from a p-and a n-type semiconductor) [32,35,36].…”

Controlled Carbon Doping in Anatase TiO2 (101) Facets: Superior Trace‐Level Ethanol Gas Sensor Performance and Adsorption Kinetics

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years, many efforts have been made toward tuning structural and electronic properties of metal oxides to reduce the working temperature and enhancing gas sensor performance. [17][18][19][20] But most of these cases, metal oxide sensors have to be operated at high temperature or under UV irradiation conditions because of their large bandgap. MOS gas sensors based chemiresistive sensors have ability to measure and monitor trace level concentration of hazardous gases such as NO x , CO x , NH 3 , CH 4 , H 2 S, and SO 2 .

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“…MOS gas sensors based chemiresistive sensors have ability to measure and monitor trace level concentration of hazardous gases such as NO x , CO x , NH 3 , CH 4 , H 2 S, and SO 2 . [17][18][19][20] But most of these cases, metal oxide sensors have to be operated at high temperature or under UV irradiation conditions because of their large bandgap. [19] Metal oxides usually display superior catalytic properties toward oxidation of reducing gas or volatile organic compounds (VOCs) at high temperature leading to change in depletion layer thickness on the metal oxide surface.…”