Toward multiscale modeling of thin-film growth processes using SLKMC
- PDF / 857,682 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 60 Downloads / 221 Views
Talat S. Rahmana) Department of Physics, University of Central Florida, Orlando, Florida 32816, USA; and Donostia International Physics Center, Donostia-San Sebastian 20018, Spain (Received 30 December 2017; accepted 13 February 2018)
The self-learning kinetic Monte Carlo method has been shown to be suitable for examining the temporal and spatial evolution of adatom islands on the (111) surface of several fcc metals, unbiased by diffusion processes chosen a priori. A pattern-recognition scheme and a diffusion path finder scheme enable collection of a large database of diffusion processes and their energetics. A variety of mechanisms involving single and multiple atoms, and concerted island motion are uncovered in long-time simulations. In this contribution, after reviewing the methodology, we present results comparing the diffusion kinetics of two sets of homo-epitaxial and hetero-epitaxial systems: small (2–8 atom) Pd and Ag islands on the respective (111) surfaces and small Cu islands on Ni(111) and Ni islands on Cu(111). We trace the dominance of concerted motion in Pd/Pd(111) and Ni/Cu(111) and competition among concerted, multiatom and single-atom processes in Ag/Ag(111) and Cu/Ni(111) to the strength of the lateral interaction among adatoms in these systems.
I. INTRODUCTION
There is preponderance of evidence that the variation of evolving morphology during thin-film growth on a surface, e.g., experimental observation of growth modes as cluster, fractal, or dendritic on fcc(111) surface,1–3 results from competition among several phenomena including surface diffusion. In fact, diffusion of adatom islands on surfaces provides important insights not only in thin-film growth4–6 but also in surface chemical reactions,7 mass transport,8 deformation,9 and corrosion,10 making it a focus of many experimental and theoretical investigations. In thin-film growth in particular, a complete understanding of its morphological evolution requires atomic-level understanding of the processes executed at early stages. Experimental observations (using scanning tunneling microscopy or field ion microscopy) of various diffusion mechanisms of islands on a surface such as edge diffusion,11,12 dimer-shearing,13,14 and concerted gliding15,16 have already pointed out the factors that may control a growth mode. However, because of insufficient time resolution, these experimental findings cannot uncover complete pathways of short-lived diffusion process; instead, on the basis of experimental evidence alone, those processes must be inferred indirectly. By contrast, a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.44
theoretical atomistic simulations are capable of determining directly the diffusion pathways and so play an important role in revealing the processes driving morphological evolution of the nanostructures. Among the available simulation techniques, one of the widely used tools at atomic resolution is molecular dynamics (MD) simulation17 which implicitly includes system vibrational and st
Data Loading...
