Formation of Co/Ge intermixing layers after Co deposition on Ge(111)2x1 surfaces

TL;DR

This study investigates the formation and atomic structure of Co/Ge intermixing layers on Ge(111)2x1 surfaces using low-temperature STM, revealing atomic mobility, accumulation at specific sites, and a reconstructed surface with altered electronic properties.

Contribution

It presents the first detailed STM analysis of Co-induced surface reconstructions and intermixing layers on Ge(111)2x1, highlighting atomic mobility and new surface periodicities.

Findings

Co atoms are immobile at 4.5K but diffuse at 80K and above.

Reconstructed Co/Ge layers form at steps, boundaries, and terraces.

Surface exhibits a double periodicity related to electronic modifications.

Abstract

The formation of a novel surface reconstruction upon Co deposition on freshly cleaved Ge(111)2x1 surfaces is studied by means of scanning tunneling microscopy (STM) at low temperature. The deposited Co atoms are immobile at substrate temperatures of 4.5K, while they can diffuse along the upper pi-bonded chains at a temperature of 80K and higher. This mobility results in accumulation of Co atoms at atomic steps, at domain boundaries as well as on atomically flat Ge terraces at, e.g., vacancies or adatoms, where reconstructed Co/Ge intermixing layers are formed. Voltage dependent STM images reveal that the newly reconstructed surface locally exhibits a highly ordered atomic structure, having the same periodicity as that of the initial 2x1 reconstruction. In addition, it shows a double periodicity along the [2-1-1] direction, which can be related to the modified electronic properties of the pi-bonded chains.