Surface Science Letters Energy scaling and surface patterning of halogen-terminated Si(0 0 1) surfaces N.A. Zarkevich * , D.D. Johnson Department of Materials Science and Engineering and the Frederich Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, USA Received 7 December 2004; accepted for publication 20 June 2005 Available online 18 July 2005 Abstract We show that steric repulsion energies between halogen dimers on a passivated Si(0 0 1) surface scale with square of the principle quantum number (or period) n of the halogen, and arise principally from bonding with Si substrate. We exemplify the scaling from previously calculated steric interactions of F, Cl, and Br, predict the interactions for I and At, and then verify the prediction by direct density-functional calculations. From the energetics, we explain the pattern- ing of the halogen-terminated Si(0 0 1), for a better understanding of the halogen-roughening process, and predict a crossover to a new vacancy-line defect for large halogens. Ó 2005 Elsevier B.V. All rights reserved. Keywords: Surface energy; Scaling; Surface structure; Morphology; Roughness; Topology 1. Introduction Halogen roughening of silicon is an important process in manufacturing silicon-based devices. During the last few years this process is also exten- sively studied experimentally with scanning tunnel- ing microscopes (STM) [1–6]. However, the science governing this process and the associated surface rearrangements are not well understood, in spite of the fact that on a Si surface halogen–halogen interactions are extremely short-ranged and domi- nated mostly by the nearest-neighbor intra- and inter-row repulsions (denoted by a and b, respec- tively). Recent measurements combined with density-functional theory (DFT) calculations have estimated steric-repulsion energies for light halo- gens on Si(0 0 1) [4]. Here we find that there is a simple scaling behavior of those energies. We show in Fig. 1 that those energies scale as n 2 , where n is the period of the halogen. From this scaling, we predict a value for iodine interactions a/2 and b, 0039-6028/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.susc.2005.06.036 * Corresponding author. Tel.: +1 217 2448487; fax: +1 217 3332736. E-mail addresses: zarkevic@uiuc.edu (N.A. Zarkevich), duanej@uiuc.edu (D.D. Johnson). Surface Science 591 (2005) L292–L298 www.elsevier.com/locate/susc