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Diameter-dependent composition of vapor-liquid-solid grown Si(1-x)Ge(x) nanowires
Xi Zhang1, Kok-Keong Lew, Pramod Nimmatoori
1Department of Materials Science and Engineering, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Nano Letters
|September 27, 2007
Summary
The germanium concentration in silicon-germanium nanowires decreases as diameter shrinks below 50 nm. This size-dependent composition is linked to Gibbs-Thomson effects in nanowire growth.
Area of Science:
- Materials Science
- Nanotechnology
- Semiconductor Physics
Background:
- Silicon-germanium (SiGe) nanowires are crucial for advanced electronic and optoelectronic devices.
- Understanding composition control during nanowire growth is essential for tailoring material properties.
- Previous studies have explored SiGe nanowire growth, but diameter-dependent composition effects require further investigation.
Purpose of the Study:
- To investigate the relationship between SiGe nanowire diameter and composition.
- To elucidate the underlying mechanisms governing size-dependent composition in SiGe nanowires.
- To provide insights into controlling SiGe nanowire properties for specific applications.
Main Methods:
- Growth of SiGe nanowires using a vapor-liquid-solid (VLS) mechanism with silane (SiH4) and germane (GeH4) precursors.
- Characterization of nanowire composition using transmission electron microscopy (TEM).
- Quantitative analysis of elemental composition via X-ray energy dispersive spectroscopy (XEDS).
Main Results:
- SiGe nanowire composition exhibits a strong dependence on nanowire diameter.
- Germanium (Ge) concentration decreases significantly in nanowires with diameters below approximately 50 nm.
- This size-dependent composition effect was observed under the studied growth conditions.
Conclusions:
- The observed decrease in Ge concentration with decreasing nanowire diameter suggests the influence of surface energy effects.
- Gibbs-Thomson effects are strongly implicated as the primary mechanism behind the size-dependent composition in SiGe nanowires.
- This finding highlights a critical phenomenon in nanowire growth that must be considered for precise material engineering.
