Ultra-low gas sensing utilizing metal oxide thin films

The structure, functionality and sensing response of metal oxide films is discussed with emphasis on ZnO and InOx prepared by Aerosol Spray Pyrolysis in ambient atmosphere and DC Magnetron Sputtering techniques under vacuum. Optical, structural and electrical characterization techniques applied for the in-depth analysis of the film properties are described. Sensing response towards ozone is presented utilizing a conventional conductivity technique as well as surface acoustic wave (SAW) structures and devices. It is shown that sensing responses of extremely low ozone concentrations in the range of a few parts per billion (ppb), at room temperature (RT), may be obtained by appropriate control of the film nanostructure. It is also shown that InOx employed as sensitive layer on top of surface acoustic wave structures can lead to strong frequency shifts for low concentrations of NO2, H2 and O3 gases.