Single- and triple-height-step distributions on Si(1 1 1) vicinal surfaces inclined toward [  1  1 2] studied by reflection electron microscopy T. Suzuki * , H. Minoda, Y. Tanishiro, K. Yagi Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan Received 21 March 2001; accepted for publication 17 September 2001 Abstract Equilibrium distributions of single- and triple-height steps (Ss and Ts) were studied on Si(1 1 1) vicinal surfaces in- clined toward [  1  1 2] by angles between 0° and 10.5°. The Ts formed at off-angles h larger than about 1.5°. The Ts coexisted with the Ss at 1:5° < h < 5°. However, the surface did not have a hill and valley structure composed of areas with only Ss or Ts. At h ¼ 5° long annealing transformed most of the Ss into Ts, so that the sparse Ss could not exist side by side. Two surface phases with regularly arranged Ts of distinct spacings of 11 and 9 nm formed at h ¼ 5° and 6°, respectively. A hill and valley structure composed of the two surface phases formed at 5° < h < 6°. Another hill and valley structure composed of the narrowly spaced surface phase (9 nm) and a surface with Miller indices ðhhmÞ ðh=m ¼ 1:4–1:5Þ formed at 6° < h < 10:5°. The ðhhmÞ structure covered most of surface at h ¼ 10:5°. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Vicinal single crystal surfaces; High index single crystal surfaces; Silicon; Reflection electron microscopy (REM) 1. Introduction Vicinal low-index Si surfaces have attracted much interest, because they exhibit an interesting surface topography (step structure). Their topo- graphy can be modified by controlling thermody- namic and kinetic parameters. For example, step bunching and faceting induced by adsorption of foreign metals, are caused by changes of the thermodynamic parameters. Step bunching and in- phase step wandering induced by direct current (dc) heating are caused by changes of the kinetic parameters [1]. In case of Si(1 1 1) vicinal surfaces, the step structures of 1  1 and 7  7 phases are different. For the 1  1 phase, single-height steps (Ss) are regularly arranged in equilibrium (smooth sur- face), while they are not regularly arranged for the 7  7 phase [2–9]. A particularly interesting case is that of vicinal surfaces inclined toward [  1  12] [4,5,7–9], where triple-height steps (Ts) are stabi- lized for off-angles h larger than about 1.3°. This was studied using low energy electron diffraction (LEED) [4] and scanning tunneling microscopy (STM) [5]. The LEED studies showed that the Surface Science 496 (2002) 179–186 www.elsevier.com/locate/susc * Corresponding author. Present address: Fritz-Haber- Institut, Max-Planck-Gesellschaft, Physikalische Chemie, Faradayweg 4-6, D-14195 Berlin, Germany. Tel.: +49-30- 8413-5201/5303; fax: +49-30-8413-5106. E-mail addresses: suzuki@fhi-berlin.mpg.de, takayuki@ surface.phys.titech.ac.jp (T. Suzuki). 0039-6028/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0039-6028(01)01633-8