Atomic layer déposition for metal oxide nanomaterials

Abstract

Solid state gas sensors based on semiconducting metal oxides have been widely investigated and utilized in environmental monitoring, chemical process controls and personal safety. In recent years, one dimensional nanostructures, such as nanowires, nanorods, nanotubes and nanobelts, have attracted much attention due to their great potential application in gas sensing, and for overcoming fundamental limitations due to their ultra high surface-to-volume ratio. A variety of methods have been developed to fabricate these nanostructures. The nanostructure based gas sensors demonstrated excellent response and recovery characteristics. However, the developed methods are not convenient for mass production and improvements on sensitivity, selectivity and long term stability are still needed. Atomic layer deposition (ALD) is a film deposition technique based on the sequential use of self-terminating surface reactions. Due to the unique nature of the reaction process, ALD becomes an ideal deposition technique to form atomic thin films and nanolaminate structures. ALD is finding ever more applications for emerging nanodevices. The potential to control thickness at the sub-nm level, and the ability to deposit thin films over highly corrugated substrates with high aspect ratio topography makes ALD of great interest in fabrication of one dimensional nanomaterial. Utilizing fabrication through nanotechnology, ALD has found new opportunities in gas sensors based on metal oxide semiconductors. In this chapter, the general characteristics of atomic layer deposition, the sensing performance enhancements by quasi-1 dimensional nanostructures and nanomaterials, the method to fabricate such nanostructures and the recent exploration of ALD in gas sensing studies are reviewed.