APS March Meeting, Denver, CO, 3/5 - 3/9/07

Heterogeneity in Ultrathin Films Simulated by Monte Carlo Method

Jiebing Sun (UNH), James B. Hannon (IBM Research Div.), Gary L. Kellogg (Sandia Nat. Labs), Karsten Pohl (UNH)

The 3D composition profile of ultra-thin Pd films on Cu(001) has been experimentally determined using low energy electron microscopy (LEEM)1. Quantitative measurements of the alloy concentration profile near steps show that the Pd distribution in the 3rd layer is heterogeneous due to step overgrowth during Pd deposition. Interestingly, the Pd distribution in the 2nd layer is also heterogeneous, and appears to be correlated with the distribution in the 1st layer. We describe Monte Carlo simulations that show that correlation is due to Cu-Pd attraction, and that the 2nd layer Pd is, in fact, laterally equilibrated. By comparing measured and simulated concentration profiles, we can estimate this attraction within a simple bond counting model.

1 J.B. Hannon, J. Sun, K. Pohl, G.L. Kellogg, Phys. Rev. Lett. 96, 246103 (2006).

Work at the University of New Hampshire is supported by the NSF under Grant No. DMR-0134933. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. DOE's NNSA under Contract DE-AC04-94AL85000.