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Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials
Published on: September 26, 2014
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Two-Dimensional Phononic Crystals: Disorder Matters.
Markus R Wagner1, Bartlomiej Graczykowski1, Juan Sebastian Reparaz1
1Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology , Campus UAB, Bellaterra, 08193 Barcelona, Spain.
Nano Letters
|September 1, 2016
Summary
Disorder in phononic crystals (PnCs) affects hypersonic properties like phonon dispersion and coherence. However, it does not impact room-temperature thermal conductivity, offering insights for predicting phonon coherence.
Area of Science:
- Materials Science
- Nanotechnology
- Acoustics
Background:
- Phononic crystals (PnCs) are crucial for controlling nanoscale heat and sound propagation.
- Experimental data on the effects of disorder on PnC phononic properties is limited.
- Understanding disorder is key to optimizing PnC applications.
Purpose of the Study:
- To experimentally investigate the influence of disorder on hypersonic and thermal properties of 2D PnCs.
- To compare the effects of ordered versus disordered lattices on phononic behavior.
- To establish criteria for predicting phonon coherence based on disorder and roughness.
Main Methods:
- Fabrication of ordered and disordered 2D phononic crystals in silicon membranes.
- Ultrafast pump-probe spectroscopy (asynchronous optical sampling) for gigahertz (GHz) hypersonic properties.
- Raman thermometry for terahertz (THz) thermal properties.
- Finite element method simulations for phonon dispersion and displacement fields.
Main Results:
- Increased surface roughness and short-range disorder modify phonon dispersion and coherence in the GHz range.
- Room-temperature thermal conductivity remains unaffected by the investigated levels of disorder.
- Hypersonic vibrations were identified using simulations.
Conclusions:
- Disorder significantly impacts GHz-range phonon coherence and dispersion in PnCs.
- Thermal conductivity at room temperature is robust against surface roughness and short-range disorder.
- A predictive framework for phonon coherence can be developed based on disorder and surface characteristics.
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