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 u sed together in the design and fabrication of advanced sensor componen ts based on gas-induced variations in electronic properties. Surface s pectroscopies 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 constr uct faster, more reliable gas sensors rely upon model studies (on crys talline materials) which attempt to isolate adsorption/desorption, dis sociation, diffusion and Schottky barrier modulation phenomena. Guided by such results, microstructure-controlled films and selectivity-enha ncing adlayers are deposited and the composites are evaluated for perf ormance characteristics and stability under various operating conditio ns. 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 a re expected to make toward future generations of gas sensors is also d iscussed.