AVS 51st International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM3
Durability Studies of MEMS/NEMS Materials/Coatings at High Sliding Velocities (upto 10 mm/s) Using a Modified AFM

Tuesday, November 16, 2004, 9:00 am, Room 213C

Session: MEMS and NEMS: Enabling Tools for Scientific Research
Presenter: N.S. Tambe, The Ohio State University
Authors: N.S. Tambe, The Ohio State University
B. Bhushan, The Ohio State University
Correspondent: Click to Email
Most micro/nanoelectromechanical (MEMS/NEMS) devices and components operate at very high sliding velocities (of the order of tens of mm/s to few m/s). Micro/nanoscale tribology and mechanics of these devices is crucial for evaluating reliability and failure issues. Atomic force microscopy (AFM) studies to investigate potential materials/coatings for these devices have been rendered inadequate due to inherent limitations on the highest sliding velocities achievable with commercial AFMs. We have developed a new technique to study nanotribological properties at high sliding velocities (upto 10 mm/s) by modifying the commercial AFM setup with a customized closed loop piezo stage for mounting samples. Durability of various materials/coatings used for MEMS/NEMS applications such as silicon, diamondlike carbon (DLC), polydimethlysiloxane (PDMS), polymethylmethacrylate (PMMA), self assembled monolayer of hexadecanethiol (HDT) and perfluropolyether Z-DOL are studied at various normal loads and sliding velocities ranging between 1 µm/s and 10 mm/s. The effect of different sliding materials on the interface wear is studied by using three different AFM tips, viz. Si, Si@sub 3@N@sub 4@ and diamond. The tip wear is monitored by measuring the tip radii. The primary wear mechanisms for the different samples at high velocities are deformation of the contacting asperities due to impacts as in the case of single crystal silicon; phase transformation from amorphous to low shear strength graphite as found for DLC; localized melting due to high frictional energy dissipation as found for PDMS and PMMA; and substrate wear as found for HDT and Z-DOL. An analytical model is presented to explain wear mechanisms and different wear regimes at high sliding velocities.