Atomic structure of Ge quantum dots on the Si(001) surface

TL;DR

This study investigates the atomic structure of Ge quantum dots on Si(001) surfaces, revealing detailed facet structures and proposing models that explain their morphology and shape stability.

Contribution

It provides the first detailed atomic models of {105} facets in Ge hut clusters, distinguishing pyramids and wedges and explaining their shape stability.

Findings

Identified identical {105} facet structures in pyramids and wedges

Revealed differences in vertex and ridge structures

Proposed models explaining shape stability and transition limitations

Abstract

In situ morphological investigation of the {105} faceted Ge islands on the Si(001) surface (hut clusters) have been carried out using an ultra high vacuum instrument integrating a high resolution scanning tunnelling microscope and a molecular beam epitaxy vessel. Both species of hut clusters--pyramids and wedges--were found to have the same structure of the {105} facets which was visualized. Structures of vertexes of the pyramidal clusters and ridges of the wedge-shaped clusters were revealed as well and found to be different. This allowed us to propose a crystallographic model of the {105} facets as well as models of the atomic structure of both species of the hut clusters. An inference is made that transitions between the cluster shapes are impossible.