Single- and triple-height-step distributions on Si(1 1 1) vicinal surfaces inclined toward [1̄ 1̄ 2] studied by reflection electron microscopy

Equilibrium distributions of single- and triple-height steps (Ss and Ts) were studied on Si(1 1 1) vicinal surfaces inclined toward [1̄ 1̄ 2] by angles between 0° and 10.5°. The Ts formed at off-angles θ larger than about 1.5°. The Ts coexisted with the Ss at 1.5°<θ<5°. However, the surface did not have a hill and valley structure composed of areas with only Ss or Ts. At θ=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 θ=5° and 6°, respectively. A hill and valley structure composed of the two surface phases formed at 5°<θ<6°. Another hill and valley structure composed of the narrowly spaced surface phase (9 nm) and a surface with Miller indices (h h m) (h/m=1.4–1.5) formed at 6°<θ<10.5°. The (h h m) structure covered most of surface at θ=10.5°.