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Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon
Published on: July 17, 2020
Crystallisation of amorphous germanium thin films.
G Garcia1, A F Lopeandía, A Bernardi
1Grup de Nanomaterials i Microsistemes, Departament de Física, UAB, 08193 Bellaterra, Spain.
Journal of Nanoscience and Nanotechnology
|May 21, 2009
Summary
Ultrathin germanium (Ge) films avoid crystallization at higher temperatures as thickness decreases. Germanium nanocrystal formation occurs via a liquid-mediated mechanism, where a metallic liquid film dewets and solidifies into barrel-type nanocrystals.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Understanding nanocrystal formation is crucial for advanced electronic and optical devices.
- Amorphous silicon dioxide/germanium/silicon dioxide (SiO2/Ge/SiO2) trilayers are promising for novel applications.
- Controlling the amorphous-to-crystalline (a-to-c) transition in thin films is a key challenge.
Purpose of the Study:
- To investigate the mechanism of germanium nanocrystal formation in ultrathin SiO2/Ge/SiO2 trilayers.
- To determine the influence of annealing temperature and amorphous germanium (a-Ge) layer thickness on nanocrystal formation.
- To elucidate the role of a liquid-mediated mechanism in Ge nanocrystal growth.
Main Methods:
- Utilized cross-sectional transmission electron microscopy (TEM) and scanning electron microscopy (SEM).
- Employed Raman scattering spectroscopy for material characterization.
- Grew ultrathin SiO2/Ge/SiO2 trilayers using e-beam evaporation.
Main Results:
- Decreasing a-Ge thickness significantly increases the annealing temperature required for the a-to-c transition.
- Films below 2 nm thickness can avoid crystallization altogether.
- Germanium nanocrystals form around 900 degrees C through a liquid-mediated mechanism.
- Observed metallic liquid film dewetting, forming droplets that solidify into barrel-type nanocrystals.
Conclusions:
- The thickness of the a-Ge layer is a critical parameter controlling the crystallization behavior.
- A liquid-mediated mechanism, involving dewetting and solidification, drives Ge nanocrystal formation.
- These findings provide insights into controlling nanocrystal morphology and crystallization in ultrathin films.
