Chemical Sensors for CVD Processing

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ABSTRACT Proposal Title: Chemical Sensors for CVD Processing Proposal Number: CTS-9810176 Principal Investigator: Arthur B. Ellis and Thomas F. Kuech Institution: U. Wisconsin - Madison The proposed research objective is to attain better physicochemical understanding of the interfaces between doped II-VI and III-V semiconductor surfaces and chemisorbed gases of III-VI compound semiconductor precursors. Prior work demonstrated that the semiconductor photoluminescence can be made more or less sensitive and selective with respect to adsorbate by appropriate surface passivation or modification. This work will produce a description of surface bonding and Fermi level of the substrate upon exposure of GaAs to SeS2, and structural changes of CdSe upon adsorption of silapentanes. Techniques to be used include photoreflectance spectroscopy, synchrotron IR absorption to detect Fermi level changes, and scanning probe microscopy. Surface modification will be performed with metalloporphyrin films, bifunctional molecules like phenylenediamine and dendrimers, and also by molecular imprinting by polymerization around analyte molecules. Heterostructures produced by MO-CVD will consist of ZnSe atop GaAs and CdSe atop GaSb. The buried interfaces will characterized from the photoluminescence response. Practical sensors will be tested for the gases adsorbed during the metallo-organic vapor phase epitaxy process. The Chemistry-Chemical Engineering collaboration has a strong influence both on the research and the educational impacts of this work. The immediate applicability of these fundamental results to CVD gas detection can be extended to the detection of hazardous gases, explosives, and food quality.