Inherent surface roughening as a limiting factor in epitaxial cluster deposition K. Meinander * , K. Nordlund, J. Keinonen Accelerator Laboratory, University of Helsinki, P.O. Box 43, Helsinki 00014, Finland Abstract Deposition of nanoclusters at thermal energies will result in an onset of roughening of the deposited surface. In order to grow epitaxial films using cluster deposition at soft landing conditions, the effect of this inherent surface roughness on the alignment of deposited clusters must be investigated. Using molecular dynamics computer simulations we have determined the maximum size of Cu clusters that will align epitaxially, upon deposition at thermal energies, on rough (1 0 0) Cu substrates with temperatures ranging from 0 K to 750 K. We have also shown that the likelihood of epitaxial alignment for the resulting structures is dependent on the point of impact of a cluster relative to previously deposited clusters. Ó 2004 Elsevier B.V. All rights reserved. PACS: 61.46.+w; 82.20.Wt Keywords: Clusters; Molecular dynamics; Epitaxy; Deposition process 1. Introduction The use of nanocluster deposition as a means of thin film growth has been widely researched throughout the past two decades [1,2]. The leading candidate among cluster deposition techniques has long been energetic cluster impact (ECI) methods [3], due to their performance as growth processes for high quality thin films, coupled with their ten- dency towards facilitating a natural smoothing of the produced film. Despite this, deposition of nanoclusters at thermal energies is also a method with alluring properties. The prospect of growing structured thin films, at conditions which are gentle towards the under- lying substrate, by using pre-structured nanoclus- ters has facilitated the study of interactions between clusters and the surfaces upon which they are deposited. One possible application is the growth of nanocrystalline thin films, where the average grain size is of the same order in size as 0168-583X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2004.10.025 * Corresponding author. Tel.: +358 9 191 50088; fax: +358 9 191 50042. E-mail address: kmeinand@acclab.helsinki.fi (K. Meinander). Nuclear Instruments and Methods in Physics Research B 228 (2005) 69–74 www.elsevier.com/locate/nimb