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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Alloying mechanisms for epitaxial nanocrystals.
M S Leite1, G Medeiros-Ribeiro, T I Kamins
1Laboratório Nacional de Luz Síncrotron, Caixa Postal 6192, CEP 13083-970, Campinas, SP, Brazil.
Physical Review Letters
|May 16, 2007
Summary
This study reveals how alloying mechanisms like intermixing and diffusion shape germanium-silicon (Ge:Si) nanocrystals. Growth conditions and annealing environments dictate whether surface or intraisland diffusion dominates, controlling alloy composition.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Physics
Background:
- Epitaxial nanocrystals are crucial for advanced electronic devices.
- Understanding alloying mechanisms is key to controlling nanocrystal composition and properties.
- Germanium-Silicon (Ge:Si) islands are model systems for studying alloying in semiconductor nanostructures.
Purpose of the Study:
- To investigate the distinct mechanisms governing the alloying of epitaxial Ge:Si nanocrystals.
- To determine the relative contributions of intermixing, surface diffusion, and intraisland diffusion.
- To correlate these mechanisms with specific growth conditions and annealing environments.
Main Methods:
- Utilized chemical vapor deposition (CVD) to grow dome-shaped Ge:Si (001) islands.
- Varied growth rates and annealing environments (H2 and PH3) to study alloying.
- Analyzed composition profiles to evaluate the impact of different diffusion mechanisms.
Main Results:
- Reduced intermixing during growth was observed for samples deposited at faster rates.
- Silicon (Si) surface diffusion was found to be dominant during annealing in a hydrogen (H2) environment.
- Germanium (Ge) surface diffusion and intraisland diffusion were prevalent during annealing in a phosphine (PH3) environment.
Conclusions:
- The composition profile of Ge:Si islands is determined by a combination of intermixing, surface diffusion, and intraisland diffusion.
- Growth rate significantly influences intermixing during the epitaxial growth phase.
- The choice of annealing gas (H2 or PH3) selectively activates different diffusion pathways, enabling control over alloy composition.
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