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Confined phonons in Si nanowires
K W Adu1, H R Gutiérrez, U J Kim
1Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Nano Letters
|March 10, 2005
Summary
Raman spectroscopy reveals how phonon confinement changes in silicon nanowires (Si NWs) as their diameter shrinks. The study found this effect aligns with a model, with a key parameter showing no diameter dependence for NWs between 4-25 nm.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Silicon nanowires (Si NWs) are crucial in nanoelectronics.
- Understanding phonon behavior in Si NWs is key to their application.
- Phonon confinement effects are diameter-dependent in nanomaterials.
Purpose of the Study:
- To investigate the evolution of phonon confinement in Si NWs.
- To correlate Raman spectral changes with Si NW diameter.
- To validate and refine existing theoretical models for phonon confinement.
Main Methods:
- Utilized Raman microprobe spectroscopy.
- Studied long crystalline silicon nanowires with varying diameters.
- Analyzed the downshift and broadening of the Si Raman band (~520 cm-1).
Main Results:
- Observed a downshift and asymmetric broadening of the Raman band with decreasing wire diameter.
- Results agree well with a phenomenological confinement model.
- An adjustable parameter (alpha) in the model was found to be insensitive to diameter (4-25 nm).
Conclusions:
- Demonstrated the direct link between Si NW diameter and phonon confinement.
- Validated the applicability of the Richter et al. model with an added parameter.
- The phonon confinement parameter is robust across a range of small nanowire diameters.