Regular step distribution of the bare Si(553) surface

Vicinal Si(111) surfaces are known to undergo faceting when the temperature is lowered below the $(1\times 1)$ to $(7\times 7)$ phase transition temperature. Depending on the cutoff angle value and direction with respect to the crystallographic axis, various facets, together with low Miller index terraces, are formed. Here, we report the formation of regularly distributed steps over macroscopic sample regions of the bare Si(553) surface. The surface morphology is studied with scanning tunneling microscopy and reflection high energy electron diffraction techniques. The (111) terraces of 2.88 nm in width, which are separated by double atomic height steps, reveal an unusual reconstruction. However, the electronic structure determined with angle resolved photoemission spectroscopy shows bands very similar to those observed for the $\mathrm{Si}\left(111\right)\text{−}(7\times 7)$ surface.

Figure 1

RHEED patterns of the Si(553) sample annealed at $450{}^{\circ }\mathrm{C}$ with an electron beam along $\left[1\overline{1}0\right]$ (a) and (c). (a) The 0th Laue zone. (b) Intensity profile (black lower line) taken from the pattern of (a) and from Si(553)-Au (blue upper line) for comparison. (d) Intensity profile taken from the diffraction pattern shown in (c). $g_{\left[1\overline{1}0\right]}=\frac{2\pi }{3.84} \AA {}^{-1}$.

Figure 2

(a) $150\text{nm}\times 150\text{nm}$ ($U=-1.5$ V, $I=0.20$ nA) and (c) $20\text{nm}\times 20\text{nm}$ ($U=1.0$ V, $I=0.15$ nA) STM images of Si(553) annealed at $450{}^{\circ }\mathrm{C}$. (b) and (d) profiles taken along the lines shown in (a) and (c), respectively. (e) $10\text{nm}\times 10\text{nm}$ ($U=0.5$ V) STM image with a marked step direction and outlined surface unit cell. (f) Sketch of the $(7\times 7)$ reconstruction with circles indicating adatoms. Blue squares in (e) indicate adatoms with similar locations as in (f).

Figure 3

(a) RHEED pattern of Si(553) annealed at $600{}^{\circ }\mathrm{C}$ with the electron beam along $\left[1\overline{1}0\right]$. (b) RHEED intensity profiles taken along the $\left[1\overline{1}0\right]$ direction for Si(553) annealed at $520$ and $600{}^{\circ }\mathrm{C}$. $g_{\left[1\overline{1}0\right]}=\frac{2\pi }{3.84} \AA {}^{-1}$.

Figure 4

Photoemission intensity maps (second derivative) of Si(553) annealed at (a), (c) $450{}^{\circ }\mathrm{C}$ and (b) Si(553)-Au. Zero binding energy denotes the Fermi level position.