Pb nanoribbons on the Si(553) surface

The crystallographic structure and morphology of the Si(553) surface ordered by Pb atoms are investigated with the reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and density functional theory (DFT) techniques. Adsorption of 1.3 monolayers of Pb, and a subsequent gentle annealing, causes regular distribution of Si atomic steps over the macroscopic sample area. The step periodicity is exactly the same as in the case of the Au-induced Si(553). However, the hybridization between Pb and Si atoms is weaker, as compared to Au and Si atoms on the Si(553) surface. Instead of two Au atomic chains strongly bonded to Si atoms, Pb forms a five-atom-wide nanoribbon on each Si(111) terrace. The simulated STM topography images obtained with the DFT calculations agree very well with the results obtained in the RHEED and STM experiments.

Figure 1

(a) RHEED pattern of Si(553)-Pb recorded with electron beam parallel to the step edges. (b) Intensity profile from the RHEED pattern of (a). (c) Intensity profile taken from the RHEED pattern with electron beam perpendicular to the step edges. (d) Ratio of the intensity of Si (10) and (00) diffraction spots vs Pb coverage.

Figure 2

(a) $50\text{nm}\times 50$ nm STM image of Si(553)-Pb. $\mathit{\text{U}}=-0.3$ V, $\mathit{\text{I}}=1$ nA. (b) $8\text{nm}\times 8$ nm STM image of Si(553)-Pb, $\mathit{\text{U}}=+0.3$ V, $\mathit{\text{I}}=1$ nA. (c) Profile taken along the line shown in (a). (d) Profile taken along the line shown in (b).

Figure 3

Structural model (a) and (b), and simulated STM image (c) of Si(553)-Pb. Topmost atoms in (a) denote Pb.