Electronic structure of the $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface: High-resolution ARPES and STM investigation

The electronic structure of a single domain $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface has been investigated by high-resolution angle-resolved photoelectron spectroscopy and scanning tunneling microscopy (STM). Four semiconducting surface states with flat dispersions, whose binding energies are 0.2, 0.4, 0.75, and 1.0 eV, were observed in the bulk band gap and more than six states were observed within the projected bulk band at binding energies less than 5.2 eV. The origins of the four surface states and of one state at a binding energy of approximately 1.5 eV at the $\overline{\Gamma }$ point are discussed based on the local density of states mappings obtained by STM. Further, a structural model that can explain all these five states is proposed.

Figure 1

LEED pattern of the $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface obtained at 100 K with a primary electron energy of 36 eV and the surface Brillouin zone of the $\text{Si}\left(110\right)\text{−}\left(1\times 1\right)$ surface. $16\times$ spots are clearly observed along the $\left[\overline{1}1\overline{1}\right]$ direction.

Figure 2

(Color online) $\text{Si}2p$ core-level spectrum of the $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface measured at $h\nu =130\text{eV}$ and ${\theta }_e=55°$. The open circles are the experimental data and the solid line overlapping the open circles is the result of the fit. Each component is indicated by different shading. The difference between the experimental data and the fit is shown by the lowermost solid line.

Figure 3

(Color online) Band dispersions of the $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface measured along the (a) $\overline{\Gamma }\text{−}\overline{X^{\prime }}$, (b) $\overline{\Gamma }\text{−}\overline{X}$, and (c) $\overline{\Gamma }\text{−}\overline{M}$ directions using $h\nu =21.2\text{eV}$. The shaded areas are the bulk band projection taken from Ref. 31 and the vertical dashed lines represent the symmetry points indicated at the top of each figure.

Figure 4

(Color online) Band dispersions of the $\text{Si}\left(110\right)\text{−}\left(16\times 2\right)$ surface measured from the $\overline{X^{\prime }}$ point to the $\overline{\Gamma }$ point of the second Brillouin zone along the $\left[00\overline{1}\right]$ direction.

Figure 5

(Color online) LDOS mappings at $E_B=\left(\text{a}\right)$ 0.2 eV, (b) 0.4 eV, (c) 0.7 eV, (d) 1.0 eV, and (e) 1.4 eV. The upper parts in (a)–(d) are overlapped with STM images to obtain information about the relation between the LDOS and surface structure. The inset in (e) and (f) are STM images obtained at sample biases of $-0.8$ and $-1.0\text{V}$, respectively.

Figure 6

(Color online) (a) STM image obtained at a sample bias of $+0.6\text{V}$. A pair of pentamers is indicated at the left side of the figure. (b) ATI model on top of the STM image and (c) the AB model proposed in this paper. The solid lines connecting the adatoms in (a) and (c) are drawn to clarify the pentagonal shape (they do not represent bonds between adatoms).