Nucleation and Growth Mechanism of a Covalent Material: Magic Clusters and Chemical Reactions

TL;DR

This study uses scanning tunneling microscopy to investigate the early nucleation and growth of silicon on a Pb-covered Si(111) surface, revealing the role of mobile magic clusters and their chemical reactions in covalent material formation.

Contribution

It introduces a new scenario based on magic clusters and their chemical reactions to explain nucleation and growth in covalent materials.

Findings

Identification of highly mobile Si magic clusters on defect-free surfaces

Observation of stable cluster aggregates lasting days at room temperature

Proposal of a chemical reaction-based nucleation and growth mechanism

Abstract

With scanning tunneling microscopy, we study the very early stage of Si deposition on a Pb monolayer covered Si(111) surface. We find a special type of Si magic clusters which are highly mobile on the defect-free surface but may be trapped temporarily at certain boundary or defect sites. They may also aggregate and a special aggregate arrangement is found to be stable for one to two days at room temperature. Adding more Si on the cluster aggregate can transform it into a metastable structure. A scenario based on magic clusters and their chemical reactions is proposed to describe the nucleation and growth processes of covalent materials.