The geometry of Bi nanolines on Si(0 0 1) R.H. Miwa a , J.M. MacLeod b , G.P. Srivastava c, * , A.B. McLean b a Faculdade de Fı ´sica, Universidade Federal de Uberla ˆndia, C.P. 593, 38400-902 Uberla ˆndia, MG, Brazil b Department of Physics, Queen’s University, Kingston, Ont., Canada K7L 3N6 c School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK Received 26 May 2004; accepted 6 October 2004 Available online 30 December 2004 Abstract A study of the Bi nanoline geometry on Si(0 0 1) has been performed using a combination of ab initio theoretical technique and scanning tunnelling microscopy (STM). Our calculations demonstrate decisively that the recently proposed Haiku geometry is a lower energy configuration than any of the previously proposed line geometries. Furthermore, we have made comparisons between STM constant-current topographs of the lines and Tersoff–Haman STM simulations. Although the Haiku and the Miki geometries both reproduce the main features of the constant-current topographs, the simulated STM images of the Miki geometry have a dark stripe between the dimer rows that does not correspond well with experiment. # 2004 Elsevier B.V. All rights reserved. PACS: 73.20.r; 73.20.At; 73.21.Hb Keywords: Silicon surface; Ab initio calculations; Nanolines; Scanning tunnelling microscopy; Semiconductor hetero-epitaxy Bismuth has been found to exhibit two distinct structural patterns of adsorption on the Si(0 0 1) surface. When it is deposited onto a room temperature Si(0 0 1) surface and the surface is subsequently annealed at 350 8C, the Bi adsorbates form an ordered (2  n) surface mesh where the value of n depends upon the duration of the annealing cycle [1]. The 2 superlattice period is produced by the formation of Bi- dimers and the n superlattice period arises from ordered rows of Bi-dimer vacancies that relax strain in the Bi overlayer. By raising the substrate temperature above the Bi desorption temperature, the Bi atoms can be coerced into a self-organized nanoline (hereafter line) structure with a high degree of order. The lines are grown either by (1) depositing Bi onto a room temperature Si(0 0 1) surface and annealing it above the Bi desorption temperature (T d  500 8C), or (2) by depositing Bi onto a surface that is maintained at a temperature that is above T d [2,3]. This is an unusual growth methodology and the lines are of particular interest because of their high structural quality. Clearly understanding why line structures with a width of only 1.5 nm and lengths of up to 500 nm form on Si(0 0 1) will have important implications for www.elsevier.com/locate/apsusc Applied Surface Science 244 (2005) 157–160 * Corresponding author. Tel.: +44 1392 264080; fax: +44 1392 264111. E-mail address: gps@excc.ex.ac.uk (G.P. Srivastava). 0169-4332/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2004.10.075