Metal Oxide Nanowires as Gas Sensing Elements: from Basic Research to Real World Applications
21 Sep 2009 | Online Presentations | Contributor(s): Andrei Kolmakov
Quasi 1-D metal oxide single crystal chemiresistors are close to occupy their specific niche in the real world of solid state sensorics. Potentially, the major advantage of this kind of sensors with respect to available granular thin film sensors will be their size and stable, reproducible and quantifiable performance in a wide range of operating conditions. The performance of such a gas sensor and especially its sensitivity is determined by its materials-specific surface chemistry as well as the size and shape of its active element(s). We report on the array of methods that allow one to fabricate, functionalize and characterize chemiresistors and chemi-FETs made of metal oxide nanowires. In particular, we grow nanowires with pre-programmed morphologies, which are most suitable for sensorics applications. To evaluate the heat management in the chemiresistor device we have performed a comparative study of the nanostructures with different thermal coupling with the support. To address the surface chemistry of the nanowires with greater details, we have tested a range of spectroscopy and imaging techniques to address local transport particularities taking place in the individual operating metal oxide nanostructure sensor. In particular, we were using Scanning Surface Potential Microscopy (SSPM) to investigate dc potential distributions in an operating device. We also have successfully implemented synchrotron radiation based photoelectron emission spectro- microscopy (PEEM) to explore submicron compositional and electronic (work function) inhomogeneouties in individual metal oxide nanowire wired as a chemiresistor. Finally, recent real world prototype devices such as gas sensors and e-noses based on metal oxide nanowires will be discussed.