DFT study of Pt-induced Ge(001) reconstructions

TL;DR

This study uses density functional theory to analyze Pt-induced Ge(001) surface reconstructions, revealing atomic arrangements that explain the formation of stable nanowire arrays observed experimentally.

Contribution

It provides a detailed atomic-level understanding of Pt-Ge surface reconstructions, clarifying the location of Pt atoms responsible for nanowire formation.

Findings

Pt atoms are located in the top surface layer.

Reconstructed surface has rows of alternating Pt-Ge and Ge-Ge dimers.

Second or third layer Pt atoms do not match experimental STM images.

Abstract

Pt deposited on a Ge(001) surface spontaneously forms nanowire arrays. These nanowires are thermodynamically stable and can be hundreds of atoms long. The nanowires only occur on a reconstructed Pt-Ge-surface where they fill the troughs between the dimer rows on the surface. This unique connection between the nanowires and the underlying substrate make a thorough understanding of the latter necessary for understanding the growth of the nanowires. In this paper we study possible surface reconstructions containing 0.25 and 0.5 of a monolayer of Pt. Comparison of calculated STM images to experimental STM images of the surface reconstruction reveal that the Pt atoms are located in the top layer, creating a structure with rows of alternating Pt-Ge and Ge-Ge dimers in a c(4x2) arrangement. Our results also show that Pt atoms in the second or third layer can not be responsible for the experimentally observed STM images.