Surface Diffusion - It Is Not Trivial

Friday, April 17, 2009
9:00 - 10:00 AM
Room 229, Norris Hall

Dr. Chun-Wei Pao
Theoretical Division, Los Alamos National Laboratory
Los Alamos, NM

Surface diffusion is critical for thin film growth processes. Recently, it has also been demonstrated that surface diffusion is a key issue in improving the recharging speed of Lithium ion battery. In the past, adatom hopping was considered the only surface diffusion mechanism on metallic surfaces. However, with the recent advances in both computational materials science and real-time high-resolution electron microscopy, researchers have found that the surface diffusion is much more complicated than simple surface adatoms hopping. In this presentation, I will talk about a novel and surprising surface diffusion mechanism: the surface dislocation on Au. This surface dislocation is formed by collective injection of surface adatoms into the surface, and forms an edge-dislocation like structure. This surface dislocation is extremely mobile and is a very efficient mechanism of surface diffusion. I will present atomistic calculation results in the thermodynamic and kinetic properties of surface dislocations. I will also present long-time scale atomistic scale simulation of surface dislocation using temperature accelerated dynamics (TAD). The simulation results fit experimental observations extremely well and provide valuable insights in understanding the properties of surface dislocations.

Biography
Dr. Chun-Wei Pao is a post-doctoral research associate in Theoretical Division at Los Alamos National Laboratory. His research interests include applying accelerated molecular dynamics (AMD) simulations to simulate thin film growth and defects/impurity diffusion in materials, in particular, in materials subjected to stress field. He received his Ph.D. degree from Mechanical and Aerospace Engineering Department at Princeton University in October 2007 under the supervision of Prof. David J. Srolovitz. His Ph.D. works were focused on studying thin film growth stresses from both atomistic scale simulations and continuum level modeling. Dr. Chun-Wei Pao can be reached at Theoretical Division, Mail Stop B268, Los Alamos National Laboratory, Los Alamos, NM 87545; email: cwpao@lanl.gov

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