Review of model sensor studies on Pd/SnO2(110) surfaces

Studies performed at the National Institute of Standards and Technology on the model gas sensor system, Pd/SnO2(110), are reviewed. Adsorption and interfacial effects play a primary role in the gas sensing process, as they do in catalysis. For this reason, researchers have used a variety of surface sensitive techniques in the research, including x ray and ultraviolet photoelectron spectroscopies (XPS and UPS), low energy electron diffraction (LEED), and ion scattering spectroscopy (ISS). By combining these complementary techniques with in situ gas response (conductance) measurements, researchers were able to correlate directly sensor activity with the composition and structure of the Pd/SnO2 interface. Although the intent of this work is to develop an understanding of gas sensing mechanisms, its relevance to Pt/SnO2 catalytic systems is obvious

Correlation of Chemisorption and Electronic Effects for Metal Oxide Interfaces: Transducing Principles for Temperature Programmed Gas Microsensors

The spectrum of chemical monitoring problems faced by the Department of Energy at its hazardous waste sites is formidable. It is likely that a variety of existing types of instrumentation will be applied in the years ahead, with varying degrees of practicality and success. A tremendous impact could be realized, however, if instrumental methods could be supplemented by a low-cost, reliable sensing technology for continuous monitoring of a range of species, including, for example, volatile organics, chlorinated hydrocarbons, ammonia, and hydrogen. To meed the diverse gas and vapor monitoring needs at ODE hazardous waste sites, the sensing system must offer, inherently, and adaptability to match the wide variety of analytes and environmental conditions that well be encountered (in tank vapor spaces, and at locations with contaminated soil or groundwater.) The purpose of this project was to investigate scientific and technical concepts that could enable a MEMS-based chemical sensing technology (developed in its foundational form at NIST during early and mid 1990's) to be made tunable for multiple target analytes in differing types of backgrounds relevant to DOE waste storage and remediatio

Coupling Nanowire Chemiresistors with MEMS Microhotplate Gas Sensing Platforms

Recent advances in nanotechnology have yielded materials and structures that offer great potential for improving the sensitivity, selectivity, stability, and speed of next-generation chemical gas sensors. To fabricate practical devices, the “bottom-up” approach of producing nanoscale sensing elements must be integrated with the “top-down” methodology currently dominating microtechnology. In this letter, the authors illustrate this approach by coupling a single-crystal SnO2 nanowire sensing element with a microhotplate gas sensor platform. The sensing results obtained using this prototype sensor demonstrate encouraging performance aspects including reduced operating temperature, reduced power consumption, good stability, and enhanced sensitivity

Correlation of Chemisorption and Electronic Effects for Metal/Oxide Interfaces: Transducing Principles for Temperature-Programmed Gas Microsensors

This research project seeks to produce, and demonstrate the utility of, a scientific database for oxide conductometric sensing materials that relates materials performance (sensitivity, selectivity and stability) to composition, microstructure and temperature. This information and the capabilities derived from it would be applied to developing a robust, low cost and application tunable chemical monitoring technology based on micromachined platforms

Correlation of Chemisorption and Electronic Effects for Metal/Oxide Interfaces: Transducing Principles for Temperature-Programmed Gas Microsensors

This Report discusses progress and accomplishments during the initial 8 months (October 1, 1998 through May 31, 1999) of a 3-year project. Work is being performed through a collaboration between NIST and the Institute for Systems Research at the University of Maryland (PI: Professor T. J. McAvoy). This three year project has a goal of producing a scientific database for conductometric sensing materials and using this information to advance gas microsensor technology. The technology will use arrays of miniature solid state devices in which adsorption of target analytes produces measurable and quantifiable changes in conductance on a suitably chosen collection of sensing materials. Microsensor development evolving from this work would allow monitoring devices to be tailored for a range of Department of Energy hazardous waste sites (and for other applications). The primary project objectives for this three year program, summarized below, have not changed from those described in our proposal document