COLL 479 |
| Dion A. Rivera, Jason R. Brown, Steven M. Thornberg, and M. Kathleen Alam. Chemical and Biological Sensing, Imaging, and Analysis, Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185-0886 |
| The process of gettering small concentrations of gases using reactive metals or ceramic oxides is important in display electronics, alkali metal dispensers for photocathode/image intensifiers, and MEMS devices. However, most investigations of getters employ techniques that do not yield a rich amount of information about the chemistry occurring at the getter surface. We have developed a technique that flashes a thin, relatively high surface area film of barium onto an infrared transparent substrate. Sections of the film a thin enough to employ FT-IR in standard transmission mode and allow high quality IR spectra to be generated. A variety of gases have been studied using FT-IR in-situ as a function of temperature to determine over temperature range gettering occurs and when irreversible chemical reaction occurs at the barium surface. Gases studied include O2, CO, CO/H2O, CO2, CH4, and CH4/H2O. Onset temperature of chemical reaction products will be discussed along with changes to this in the presence of H2O. In the case of CO and CO/H2O multivariate curve resolution was employed to separate the spectrally overlapped gas phase CO from CO adsorbed to the barium surface. Results of this analysis show that more of the CO adsorbs to the surface of the barium as the temperature in increased with oxidation of the surface occurring near 80 oC. The presence of water in the system lowers the barrier to oxidation and greatly increases the amount of adsorbed CO at lower temperatures. Results from these studies indicate that device performance at low temperatures is unpredictable and that the presence of water even in relatively low concentrations can drastically change the gettering process for a specific gas.
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Vibrational Analyses of Dry and Wet Surfaces
8:30 AM-11:30 AM, Thursday, April 1, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |