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Reversible shape evolution of Ge islands on Si(001).
A Rastelli1, M Kummer, H von Känel
1INFM-Università di Pavia, Via Bassi 6, I-27100 Pavia, Italy. rastelli@solid.phys.ethz.ch
Physical Review Letters
|December 12, 2001
Summary
Strained Germanium (Ge) islands on Silicon (Si) surfaces change shape dramatically when exposed to Si flux. This study reveals a complete reversal of morphological evolution compared to initial Ge island growth.
Area of Science:
- Materials Science
- Surface Science
- Nanotechnology
Background:
- Germanium (Ge) islands grown on Silicon (Si) substrates exhibit unique properties due to lattice mismatch.
- Understanding Ge/Si(001) island evolution is crucial for fabricating advanced semiconductor devices.
Purpose of the Study:
- To investigate the morphological evolution of strained Ge/Si(001) islands under silicon (Si) flux.
- To analyze the impact of alloying on island shape transformation.
- To develop a model explaining the observed shape changes.
Main Methods:
- Scanning tunneling microscopy (STM) was employed to observe surface morphology.
- Controlled exposure to silicon flux was used to induce changes in Ge islands.
- Analysis of island shape and facet evolution at various Si coverages.
Main Results:
- Dome-shaped Ge islands showed significant shape changes starting at 0.5 monolayer Si coverage.
- Islands transformed into [105]-faceted pyramids and subsequently into stepped mounds with <110>-oriented steps.
- Observed morphological changes were induced by alloying and reversed the initial Ge island growth patterns.
Conclusions:
- The equilibrium shape of Ge/Si(001) islands is strongly influenced by volume and composition.
- Alloying plays a critical role in the morphological reversal during Si flux exposure.
- These findings provide insights into controlling nanostructure morphology for potential applications.