AVS 61st International Symposium & Exhibition
    Surface Science Wednesday Sessions
       Session SS+AS-WeM

Paper SS+AS-WeM5
Elucidating Atomic-scale Wear Processes in Hydrocarbon-based Materials via Molecular Dynamics and AFM

Wednesday, November 12, 2014, 9:20 am, Room 312

Session: Atomistic Modeling of Surface Phenomena
Presenter: Judith Harrison, United States Naval Academy
Authors: J.A. Harrison, United States Naval Academy
T.D.B. Jacobs, University of Pennsylvania
P.L. Keating, United States Naval Academy
M. Fallet, United States Naval Academy
J.D. Schall, Oakland University
Y. Jiang, University of Pennsylvania
K.T. Turner, University of Pennsylvania
R.W. Carpick, University of Pennsylvania
K.E. Ryan, United States Naval Academy
Correspondent: Click to Email
Molecular dynamics (MD) simulations are unique in their ability to elucidate atomic-scale phenomena because the positions, velocities, and forces of all atoms in the system are known as a function of time. Atomic-scale wear in nanoscale contacts is of particular importance for tip-based nanomanufacturing applications. As a result, wear resistant materials, such as diamond-like carbon (DLC), have been used to coat AFM tips to improve the lifespan and reliability of AFM probes. We have performed atomic force microscope (AFM) experiments and MD simulations aimed at examining adhesion and wear in diamond, ultrananocrystalline diamond (UNCD), and amorphous carbon (a-C:H) materials. Specifically, we examined the normal and sliding contact of differently shaped axisymmetric tips, composed of a-C:H and UNCD, with hydrocarbon-based substrates. Specific attention was paid to elucidating specific atomic-scale wear mechanisms and their dependence on tip shape, material, surface termination, impact point, and roughness. To examine the effect of the potential energy function on wear mechanisms, identical simulations were performed with the AIREBO potential and the REBO+S potential. The AIREBO potential is based on the reactive empirical bond-order potential (REBO), which was developed to model CVD growth of diamond. Recently, it was demonstrated that the short-range cut-off for covalent bonding in the REBO potential resulted in bond-breaking forces that are an order of magnitude larger than those predicted by DFT calculations. A screening function was added to the REBO potential (REBO+S) to alleviate this situation. Simulations were carried out using each potential, and wear mechanisms identified in each set of simulations were compared.