Paper TR+AS+NS+SS-MoA3
Molecular Dynamics Simulations of Adhesion & Friction between Carbon-based Materials, Silicon, and Silicon Carbide

Monday, October 28, 2013, 2:40 pm, Room 203 C

The nanoscale properties of two bodies in contact cannot be fully analyzed on an atomistic level using experimental methods or understood solely using continuum mechanics. Molecular dynamics (MD) simulations allow nanoscale behavior to be modeled by resolving the positions, velocities, and forces of discrete atoms in the system. Diamond has been of interest as both an object of scientific study and as an ideal material for applications such as, cutting tool coatings, waste water purifiers, chemical sensors, electronic devices, and micro- and nanoelectromechanical systems (M/NEMS) because of its unique electrical, mechanical, and tribological properties. Due to its high fracture strength and chemical robustness, it can withstand exposure to harsh environments and resist mechanical wear. It can be grown in nanocrystalline form with nearly equivalent mechanical performance to the crystalline form. Silicon, due to the ability to create atomically sharp tips, is frequently used in scanning probe microscopy. Recently, carbon implantation of preformed Si-tips has been used to improve wear properties. In this work, MD was used to simulate the nanoscale adhesion and tribological behavior between diamond, diamond-like carbon (DLC) surfaces and silicon, and silicon carbide tips. Work of adhesion values from the MD simulations with axisymmetric tips are compared to, and discussed within the context of, complementary AFM experiments where available, finite element simulations, and continuum mechanics-based analytical models. MD simulations show that the work of adhesion is sensitive to the identity of the contacting materials because they have inherent roughness differences. In addition, work of adhesion values obtained from continuum mechanics-based analytical models are consistently higher than values obtained using the atomic-force microscope, which are higher than the simulated values. A recently developed bond-order potential for C-, H-, and Si-containing systems was used to carry out these simulations. The novel aspects of this model will be discussed.