IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Microelectromechanical Systems (MEMS) Thursday Sessions
       Session MM-ThM

Paper MM-ThM4
Amorphous Diamond MEMS

Thursday, November 1, 2001, 9:20 am, Room 130

Session: Characterization of MEMS Materials
Presenter: J.P. Sullivan, Sandia National Laboratories
Authors: J.P. Sullivan, Sandia National Laboratories
T.A. Friedmann, Sandia National Laboratories
M.P. de Boer, Sandia National Laboratories
M.T. Dugger, Sandia National Laboratories
M. Mitchell, Sandia National Laboratories
R.G. Dunn, Sandia National Laboratories
R. Ellis, Sandia National Laboratories
D.A. LaVan, Massachusetts Institute of Technology
Correspondent: Click to Email
Microelectromechanical systems (MEMS), including electrostatic comb drives, simply-supported beams, and tensile test specimens, have been fabricated from amorphous diamond (aD), a pure carbon material with mechanical properties similar to crystalline diamond. Measurements using aD MEMS revealed that the material has high strength (8 GPa), fracture toughness (8 MPa.m@super 1/2@), and elastic modulus (800 GPa). These properties, combined with good inherent wear resistance, makes the material useful for achieving long lifetime MEMS that have rubbing surfaces or experience impact loading. Hydrophobicity and bio-compatibility of aD were also evaluated. The water contact angle was found to range from 84° for the as-prepared MEMS material up to 94° after annealing to 850°C. The increase in contact angle with annealing is similar to that found for crystalline diamond surfaces, which is due to O desorption that leaves an H-terminated surface. The hydrophobic nature of aD greatly reduces stiction in MEMS, thus permitting release without the use of applied hydrophobic coatings or supercritical drying. Bio-compatibilty was tested through the use of cultured cell growth, using bovine capillary endothelial cells, on bare and fibronectin-coated aD surfaces. Limited cell growth and adhesion was found for the uncoated aD surface, while good growth and adhesion was found for the fibronectin-coated aD. This is desirable for the creation of bioMEMS. Finally, the very high elastic modulus of this material is desirable for achieving mechanical structures with high resonant frequency. A key requirement for mechanical oscillators used for electrical signal processing is the need for high quality factor, Q. The Q for aD MEMS oscillators operating in vacuum will be reported and compared to that found for silicon oscillators. Sandia is a multiprogram lab operated by Sandia Corp., a Lockheed Martin Co., for the U.S. D.O.E. under contract DE-AC04-94AL85000.