Atomic structure of the single step and dynamics of Sn adatoms on the Si(111)-\sqrt{3}\times\sqrt{3}-Sn surface

TL;DR

This study reveals the atomic structure of single steps on the Sn-covered Si(111) surface and investigates Sn adatom dynamics near these steps using low-temperature STM and ab initio calculations.

Contribution

It provides a detailed atomic model of step structures and explains adatom trapping and dynamics through potential double wells near the steps.

Findings

Single steps consist of Sn atomic chains.

Potential double wells trap Sn adatoms near steps.

Adatom dynamics exhibit telegraph noise at 80 K.

Abstract

The atomic structure of well-ordered single steps on the Si(111)-\sqrt{3}\times\sqrt{3}-Sn surface and the dynamics of Sn adatoms in the vicinity of these steps was studied. The work was performed using low-temperature scanning tunneling microscopy (STM) and ab initio calculations based on the density-functional theory. The STM tip was used to record the tunneling current versus time on top of oscillating adatoms, keeping the feedback loop turned off. The dynamics of adatoms, detected as the telegraph noise present in the tunneling current, was registered near the steps at 80 K. The atomic structure model of the single steps consisting of Sn atomic chains along the steps was developed. This structure leads to the formation of potential double wells near the steps acting as traps for Sn atoms and explains the fluctuating current recorded in these areas.