THE USE OF SURFACE AND THIN-FILM SCIENCE IN THE DEVELOPMENT OF ADVANCED GAS SENSORS

This paper illustrates how surface science and thin-film science are used together in the design and fabrication of advanced sensor components based on gas-induced variations in electronic properties. Surface spectroscopies are combined with electrical measurements to examine the near-surface region of materials where local chemisorption events can be transduced into measurable collective responses. Efforts to construct faster, more reliable gas sensors rely upon model studies (on crystalline materials) which attempt to isolate adsorption/desorption, dissociation, diffusion and Schottky barrier modulation phenomena. Guided by such results, microstructure-controlled films and selectivity-enhancing adlayers are deposited and the composites are evaluated for performance characteristics and stability under various operating conditions. In our research approach, analytical, deposition and modification instrumentation are combined in a single, controlled-vacuum (UHV-based) enclosure to efficiently study sensor materials and mechanisms. The impact that high-resolution, probe-tip techniques and micromachining are expected to make toward future generations of gas sensors is also discussed.