Abstract
Mechanisms of microscale wear in silicon-based microelectromechanical systems (MEMS) are elucidated by studying a polysilicon nanotractor, a device specifically designed to conduct friction and wear tests under controlled conditions. Photoelectron emission microscopy (PEEM) was combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) to quantitatively probe chemical changes and structural modification, respectively, in the wear track of the nanotractor. The ability of PEEM–NEXAFS to spatially map chemical variations in the near-surface region of samples at high lateral spatial resolution is unparalleled and therefore ideally suited for this study. The results show that it is possible to detect microscopic chemical changes using PEEM–NEXAFS, specifically, oxidation at the sliding interface of a MEMS device. We observe that wear induces oxidation of the polysilicon at the immediate contact interface, and the spectra are consistent with those from amorphous SiO2. The oxidation is correlated with gouging and debris build-up in the wear track, as measured by AFM and scanning electron microscopy (SEM).
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Acknowledgments
This study was partly funded by Air Force grant FA9550-08-1-0024, and partly by Sandia—a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. The authors thank Dr. Scholl and Dr. Doran for their help with PEEM II at the Advanced Light Source (ALS). The ALS and use of the Center for Nanoscale Materials facility are supported by the DOE under Contract DE-AC02-05CH11231 and Contract DE-AC02-06CH11357, respectively.
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Grierson, D.S., Konicek, A.R., Wabiszewski, G.E. et al. Characterization of Microscale Wear in a Polysilicon-Based MEMS Device Using AFM and PEEM–NEXAFS Spectromicroscopy. Tribol Lett 36, 233–238 (2009). https://doi.org/10.1007/s11249-009-9478-7
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DOI: https://doi.org/10.1007/s11249-009-9478-7