Surface Science
250 x 250 nm STM topograph of 2.0 monolayer-equivalent coverage of Pd on an SnO2 epitaxial film, grown on r-axis sapphire. The cross-section slice from the position indicated in the image is shown in a height vs distance plot. The metal particles are 10 to 20 nm wide and 0.5 nm high. From Poirier, G.E., Cavicchi, R.E., and Semancik, S.; J. Vac. Sci. and Tech., A12 (4), 2149-2152 (1994).Chemical microsensor researchers at NIST use surface science techniques to investigate foundational concepts which underlie future advancements in sensor design, fabrication and operation. A multi-technique surface analytical facility is used in desorption studies and mechanistic studies of metal oxide single crystals and thin film surfaces. The facility houses techniques such as scanning tunneling microscopy (STM), X-ray and UV photoemisssion spectroscopies (XPS, UPS), ion scattering spectroscopy (ISS), temperature programmed desorption (TPD) and in situ four-point conductance measurements.
Tin oxide serves as an important base material in a variety of conductance-type gas-sensing devices. Tin oxide single crystals and thin film surfaces have been examined extensively. Catalytic metal additives (Pd, Pt) are used to modify pure SnO2 surfaces, as an approach for producing enhanced responses and increased selectivity.
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Desorption |
The Tin Oxide |
Metal |
Mechanistic |