SCIENCE AND TECHNOLOGY OF ULTRANANOCRYSTALLINE DIAMOND FILMS FOR MULTIFUNCTIONAL MEMS/NEMS DEVICES

The objectives of this project are to investigate microstructure-mechanical-electronic transport property relationships of a new multifunctional material designated as ultrananocrystalline diamond (UNCD), and to utilize this material in microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). Through interdisciplinary research and educational efforts of the team members from Northwestern University (NU), University of Illinois at Chicago (UIC) and University of Missouri-Columbia (UMC), in collaboration with Argonne and Sandia National Laboratories (ANL and SNL), an integrated experimental, analytical and computational program has evolved with the following approaches: 1. Scan probe microscopy approaches, including conductive atomic force microcopy and ultra high vacuum scanning tunneling microscopy/spectroscopy, for nanoscale characterization of surface structure and conductivity of UNCD films, that will enable the microstructure to be ascertained for films made with various dopings; 2. Investigation of mechanical properties, such as Young’s modulus, hardness, plasticity, and fracture, of UNCD with varying degrees of doping at the microlevel using a recently developed membrane deflection experiment, and at the nanolevel by means of a novel MEMS loading device that can operate within various microscopes; and 3. Multiscale model-based simulation of the film deposition and growth process, and the relationship between microstucture and electro-mechanical properties of UNCD films, by using combined ab initio, molecular dynamics, kinetic Monte Carlo and continuum methods. The new methods of chemical vapor deposition (CVD) recently developed by this team make possible the manufacturing of the UNCD films that exhibit unique and outstanding properties such as high hardness, high fracture strength, high Young’s modulus, extremely low friction coefficient and high wear resistance, low residual stress in as-deposited thin films, unique field electron-emission properties, a wide range of conductivity controlled by microstructure and doping, and highly conformal films, which are all critical to MEMS/NEMS applications. The integrated experimental, analytical and computational study of the unique properties of UNCD films, via the above interdisciplinary approaches, is the first of its kind and we expect it to make an important intellectual impact on the understanding of the relationship between grain size-grain boundary chemistry and electro-mechanical properties of UNCD at the nanoscale. In particular, the atomic-scale information suitable to unraveling the electronic conduction mechanism in UNCD and the effect of its microstructure on this phenomenon could be positively used to design MEMS/NEMS devices. The preliminary results obtained from this project since it was funded in September 2003 are summarized as follows.