Bei Peng
Ph.D. Candidate, Department of Materials Science and Engineering and Nanoscale Science and Engineering Center, Northwestern University
Ultrananocrystallinde Diamond Thin Films – Mechanical Properties and NEMS Applications
Ultrananocrystalline diamond (UNCD) coating technology developed at Argonne National Laboratory provides the basis for a new Micro and Nano Electromechanical Systems (MEMS/NEMS) technology capable of yielding devices with superior performance. Preliminary work has demonstrated the feasibility of fabricating 2-D and 3-D MEMS components that can be the basis for the fabrication of complete MEMS/NEMS devices. Components such as cantilevers and devices with multiple structural UNCD layers such as microturbines have already been produced. These preliminary achievements are promising steps toward full-scale application of UNCD components in functional MEMS devices. However, before full-scale integration can occur, several intrinsic material properties, such as elastic modulus, plasticity and fracture of undoped and doped UNCD must be well characterized to fully exploit the potential of this material. The work was organized in three phases:
Phase1, Investigation of the wide range of material nanostructural features and associated electro-mechanical properties available for UNCD films using SEM, TEM, and contact AFM potentiometry techniques.
Phase2, Mechanical properties of UNCD such as elastic modulus, fracture strength, fracture toughness, and the ideal strength were investigated using a membrane deflection experiment (MDE). Particularly, the widely used Weibull statistics was applied to study the distribution of the fracture strength. The applicability of Weibull's theory in predicting the fracture strength of specimens with different sizes was verified. Multi-scale modeling and simulation of the experiments, through a two-way (bottom-up and top-down) iterative process, to elucidate the physics and properties related to UNCD was discussed.
Phase3, a novel UNCD AFM tip was designed and micro-fabricated for the contact mode AFM potentiometry. The UNCD tip is conformal, smooth, conductive, and with sharp tip radius that can have better resolution and longer life than standard AFM tips. This technique has the potential to be arrayed and actuated to detect and repair the failure of nano-circuitry.
