Metal Oxides for Room-Temperature Gas Sensors

In plasmon resonance gas sensors, which also usually operate at room temperatures, we have another situation. In these devices, in order to shift the operating point of the surface plasmon resonance toward an aqueous environment, a thin high-refractive index dielectric overlayer can be employed. The use of overlayers with higher refractive indexes allow for thinner overlayers and potentially better sensor sensitivity. Analysis of results obtained indicates that tantalum pentoxide, which has high refractive index (see Table 2.18) and good environmental stability, may be used for this purpose (Dostalek et al. 2001 Boozer 2003). 

As was shown before, conventional gas-sensing metal oxides, such as SnO, In Oj, WO3, ZnO, as a rule are used in conductometric gas sensors operated at high temperatures. However, during experiments carried out recently (last decade) it was established that conductometric gas sensors based on these metal oxides can operate at room temperatures as well. Examples of these sensors are presented in Table 2.19. 

MeOx geometry Material (grain size, nm) /oR/R) Gas tested i,(s) Reference 

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