Wave phononics
Phononic crystals have been studied for the past decades as a tool to control the propagation of acoustic and mechanical waves. Recently, researchers proposed that nanosized phononic crystals can also control heat conduction by phonon dispersion engineering using wave properties of phonons. In this project, we try to use phononic crystals to coherently control heat condution at nanoscale. We aim to experimentally test theoretical predictions of the thermal conductivity reduction caused by periodicity and local resonances.
Figure above summarizes our research on coherent thermal transport. Panel (a) shows thermal conductance “boost” effect when phononic crystal becomes more conductive than a membrane without holes due to phonon interference. Panel (b) shows tuning of thermal conductance via structure periodicity in various phononic crystals at low temperatures. Experiments on (c) hole-based phononic crystals of different lattices, (d) pillar-based phononic crystals, and (e) phononic crystals with ordered and disordered disordered lattices. At low temperatures, the difference between ordered and disordered lattices occurs, which indicates coherent regime.
Publications
Phonon dispersion of nanoscale honeycomb phononic crystal: gigahertz and terahertz spectroscopy comparison
In this work, we experimentally investigate the behavior of a honeycomb silicon phononic crystal in the gigahertz range, where the continuum approximation holds, and in the terahertz range, where the phonon wavelengths are comparable to interatomic distances.
Tailoring phonon dispersion of a genetically designed nanophononic metasurface
Using the inverse design approach, we create a two-dimensional phononic metasurface exhibiting a highly anisotropic phonon dispersion.
Phonon diffraction and interference using nanometric features
Phonon diffraction and interference patterns are observed at the atomic scale, using molecular dynamics simulations.
Impact of nanopillars on phonon dispersion and thermal conductivity of silicon membranes
We report on the fabrication and thermal measurements of silicon films with nanopillars as small as 12 nm in diameter.
Nanoscale limit of the thermal conductivity in crystalline silicon carbide membranes, nanowires, and phononic crystals
We systematically measured thermal conductivity in SiC nanostructures, including nanomembranes, nanowires, and phononic crystals.
Review of thermal transport in phononic crystals
In this article, we review the phonon and thermal transport in one and two-dimensional phononic crystals
Review of coherent phonon and heat transport control in one-dimensional phononic crystals at nanoscale
In this Research Update, we summarize the past decade of theoretical and experimental studies of coherent control of phonon and heat transport in one-dimensional phononic crystals.
Coherent and incoherent impacts of nanopillars on the thermal conductivity in silicon nanomembranes
Here, we fabricate nanopillars on suspended silicon membranes using damageless neutral-beam etching and investigate the impact of nanopillars on the thermal conductivity of the membranes in the 4–300 K range.
Thermal conductivity reduction in a silicon thin film with nanocones
We propose a cost-effective, large-area, and maskless nanofabrication method that creates external nanocones on the silicon surface while preserving its interior. Our experiments show that these nanocones reduce the thermal conductivity of thin silicon membranes by more than 40%.
Coherent thermal conduction in silicon nanowires with periodic wings
Here, we study coherent thermal conduction in silicon nanowires with added periodic wings at sub-Kelvin temperature. Our simulations show that the added periodic wings flatten the phonon dispersion and thus reduce the thermal conductance.
On the reduction and rectification of thermal conduction using phononic crystals with pacman-shaped holes
We measure the thermal conductivity of silicon phononic crystals with asymmetric holes at room and liquid helium temperatures and study the effect of thermal rectification, phonon boundary scattering, neck transmission, and hole positioning.
Phonon and heat transport control using pillar-based phononic crystals
In this review, we focus on recent theoretical and experimental advances in phonon and thermal transport engineering using pillar-based phononic crystals.
Thermal conductivity reduction in silicon fishbone nanowires
Here, we experimentally study heat conduction in silicon nanowires with periodic wings, called fishbone nanowires.
Aluminium nanopillars reduce thermal conductivity of silicon nanobeams
We experimentally investigate heat conduction in suspended silicon nanobeams with periodic arrays of aluminium nanopillars.
Heat conduction tuning by wave nature of phonons
We show a possibility to use the wave nature of heat for thermal conductivity tuning via spatial short-range order in phononic crystal nanostructures.
Heat conduction engineering in pillar-based phononic crystals
In this work, we systematically investigate how various parameters of pillar-based phononic crystals affect thermal conductance at low temperatures.
Impact of limiting dimension on thermal conductivity of one-dimensional silicon phononic crystals
We discover that the thermal conductivity does not strongly depend on the period of the phononic crystal nanostructures whereas the surface roughness and the smallest dimension of the structure—the neck—play the most important roles in thermal conductivity reduction.
Reduction of thermal conductance by coherent phonon scattering in two-dimensional phononic crystals of different lattice types
The impact of lattice type, period, porosity, and thickness of two-dimensional silicon phononic crystals on the reduction of thermal conductance by coherent modification of phonon dispersion is investigated using the theory of elasticity and the finite element method.
Reduction of thermal conductivity by surface scattering of phonons in periodic silicon nanostructures
We investigate the impact of various phonon-scattering mechanisms on the in-plane thermal conductivity of suspended silicon thin films with two-dimensional periodic arrays of holes, ie, phononic crystal (PnC) nanostructures.
Thermal conductance boost in phononic crystal nanostructures
A theoretical study of coherent phonon scattering in thin-film phononic-crystal nanostructures (also called thermocrystals) is presented.