| Phononics 2013: 2nd International Conference on Phononic Crystals/Metamaterials, Phonon Transport and Optomechanics | ||||||
| June 2-7 2013, Sharm El-Sheikh, Egypt | ||||||
| Wednesday: June 5 | Detailed Program Information | |||||
| Registration (Amaraua Foyer) | 7:30 am - 12:00 pm | |||||
| Announcements (Amaraua Conf. Hall) | 7:45 am - 8:00 am | |||||
| Track 3: Phonon Transport | ||||||
| Session: 7 (Amaraua Conference Hall) | 8:00 am - 10:20 pm | |||||
| Session Chair: Baowen Li | ||||||
| Author: C. M. Sotomayor Torres | Category: Plenary Talk | |||||
| Affiliation: Catalan Institute of Nanotechnology | ||||||
| Paper #: 0156 | Time: 8:00 am -8:30 am | |||||
| Title: Acoustic Phonons in Silicon Free-Standing Membranes: From Slow Phonons to Engineering Thermal Conductivity | ||||||
| Abstract: Confined acoustic phonons are investigated and their dispersion relations simulated and measured. Based on this we investigate the impact on thermal transport in low dimensional semiconductors and carry out simulations for thermal rectification and storage. | ||||||
| Author: D. Donadio | Category: Plenary Talk | |||||
| Affiliation: Max Planck Institute for Polymer Research | ||||||
| Paper #: 0077 | Time: 8:30 am -9:00 am | |||||
| Title: Phonon Transport in Graphene: Effects of Strain and of Finite Temperature Gradients | ||||||
| Abstract: We compute phonon transport in suspended graphene by atomistic molecular dynamics simulations. We find that whereas at equilibrium conditions the thermal conductivity of suspended graphene is finite, in the presence of finite temperature gradients it diverges with the size of graphene patches. Thermal conductivity also diverges when graphene is strained. | ||||||
| Author: I. J. Maasilta | Category: Invited Oral | |||||
| Affiliation: University of Jyväskylä | ||||||
| Paper #: 0035 | Time: 9:00 am -9:20 am | |||||
| Title: Phononic Crystals for the Control of Thermal Conduct-ance at Sub-Kelvin Temperatures | ||||||
| Abstract: I will review recent progress in fabrication, measurement and modeling of two- and three dimensional phononic crystals for controlling thermal transport in the sub-Kelvin temperature regime. Initial measurements for 2D hole-array phononic crystal samples show good agreement with the calculated ballistic thermal conductance of the modified phonon eigenmode spectrum. Somewhat surprisingly, the calculation predicts that thermal conduct-ance is enhanced at the ultralow temperature limit below 0.1 K, as compared to a full, uncut membrane. | ||||||
| Author: A. Struck | Category: Invited Oral | |||||
| Affiliation: Hochschule Rhein-Waal | ||||||
| Paper #: 0090 | Time: 9:20 am -9:40 am | |||||
| Title: Minimizing the Thermal Conductivity in Isotopic Superlattices: A Molecular Dynamical Approach | ||||||
| Abstract: Superlattice structures can be tailored to manipulate phonon propagation. Modified density of states, multiple back-reflections at interfaces, reduced effective sound velocities and localization lead to strongly altered macroscopic quantities like thermal conductivity. We have investigated to which extent the tailoring of phononic structures can reduce the thermal conductivity in isotopically enriched silicon superlattices. Based on molecular dynamical simulations (MD) we have altered design parameters such as the number of interfaces and the periodicity. In accordance to experimental investigations the thermal conductivity could be engineered in the range from 170 W/(m∙K)1 to 50 W/(m∙K)2. We also discuss the modified material properties in the context of thermoelectric applications. | ||||||
| Author: C. M. Reinke | Category: Invited Oral | |||||
| Affiliation: Sandia National Laboratories | ||||||
| Paper #: 0155 | Time: 9:40 am -10:00 am | |||||
| Title: Modified Nanoscale Phonon Transport in Phononic Crystal Devices | ||||||
| Abstract: We present an analysis of thermal conductivity reduction in micro-scale PnC devices using a method that combines the phonon dispersion of the atomic material lattice with that of the PnC lattice. The theoretical results are compared with thermal conductivity measurements of fabricated PnC samples, with good agreement observed between the thermal transport model and corresponding experimental data. | ||||||
| Author: K. Muralidharan | Category: Invited Oral | |||||
| Affiliation: University of Arizona | ||||||
| Paper #: 0103 | Time: 10:00 am -10:20 am | |||||
| Title: Analysis of Phonon Mode Lifetime in 1D and 2D Anharmonic Systems | ||||||
| Abstract: In nano-composite systems, high frequency thermal phonon modes are subject to multiple different mechanisms of decay. Of particular importance are effects related to the periodicity of the underlying structure (band-folding effects) and scattering effects related to boundaries, surfaces and interfaces as well as anharmonic effects. Thus, characterizing the thermal response of nanoscale composites requires a rigorous examination of these phenomena. In this work, we elucidate the role that band-folding and boundary scattering as well as anharmonicity play in decreasing the lifetime of high-frequency phonon modes using two novel simulation approaches. Specifically, using spectral energy density (SED)1 band structure calculations, a series of non-linear one-dimensional superlattices of masses and springs are investigated to identify the effect band-folding has on the availability of phonon-mode decay channels and phonon-mode lifetimes. Next, using the method of spatially resolved heat current autocorrelation function (HCAF) analysis, life-times of thermal phonons in two-dimensional high-Debye temperature nanophononic crystals such as boron-nitride nanoribbons with asymmetric defects are examined as a function of temperature to characterize the role of anharmonicity on phonon propagation and life-times as well as charcterize the possibility of thermal rectification in such systems. | ||||||
| Coffee Break (Amaraua Foyer) | 10:20 am - 10:40 am | |||||
| Track 3: Phonon Transport | ||||||
| Session: 8 (Amaraua Conference Hall) | 10:40 am - 1:00 pm | |||||
| Session Chair: C. M. Sotomayor Torres | ||||||
| Author: Z. C. Leseman | Category: Invited Oral | |||||
| Affiliation: University of New Mexico | ||||||
| Paper #: 0162 | Time: 10:40 am -11:00 am | |||||
| Title: Fabrication and Characterization of 2-D Phononic Crystals | ||||||
| Abstract: Techniques are described for the fabrication and characterization of nanostructured phononic crystals (PnCs). Fabrication of the PnCs is performed in Si while employing a fo-cused ion beam (FIB) to impart the nanostructure. Characterization is performed using a technique wherein the PnC is suspended between two thermally isolated islands. By raising the temperature with respect to the other the thermal conductivity of the PnC can be deter-mined. Results indicate that coherent scattering of phonons is occurring. | ||||||
| Author: O. Bourgeois | Category: Invited Oral | |||||
| Affiliation: Centre National de la Recherche Scientifique | ||||||
| Paper #: 0112 | Time: 11:00 am -11:20 am | |||||
| Title: Phonon Thermal Transport in Periodically Structured Nanosystems | ||||||
| Abstract: We report on the transport of thermal phonons in periodic nano-objects. The thermal conductance of suspended nanosystems (nano-engineered membranes, nanowires) has been measured down to very low temperature. It is shown that the presence of periodic structures (corrugation, lattice of holes) may strongly reduce the heat transfer in these nanosystems. | ||||||
| Author: S. Sinha | Category: Invited Oral | |||||
| Affiliation: University of Illinois at Urbana-Champaign | ||||||
| Paper #: 0142 | Time: 11:20 am -11:40 am | |||||
| Title: Phonon Transport in Periodic 3-Dimensional Nanostructures | ||||||
| Abstract: We report measurements and modeling of thermal conductivity in periodic three-dimensional dielectric nanostructures: silicon inverse opals. The periodicities and shell thicknesses are in the range 420-900 nm and 18-38 nm respectively. The material thermal conductivity is in the range 5-12 W/mK at 300 K and has an anomalous ~T1.8 dependence at low temperatures, distinct from the typical ~T3 behavior of bulk polycrystalline silicon. Using phonon scattering theory, we show such dependence arising from coherent phonon reflections in the inter-grain region. | ||||||
| Author: R. Chen | Category: Invited Oral | |||||
| Affiliation: University of California | ||||||
| Paper #: 0171 | Time: 11:40 am -12:00 pm | |||||
| Title: Thermal and Thermoelectric Transport in Thin Nanowires | ||||||
| Abstract: Thermal and thermoelectric transport in small diameter nanowires where both heat and charge carriers (phonons and electrons) are confined have been rarely probed experimentally due to several changes associated with the small size. In this presentation, we will present our recent progress on experimental study of thermal conductivity and thermoelectric power factor in small diameter Ge and Ge-Si nanowires. | ||||||
| Author: Baowen Li | Category: Org. Colloquium | |||||
| Affiliation: National University of Singapore | ||||||
| Paper #: 0128 | Time: 12:00 pm -12:20 pm | |||||
| Title: Anomalous Phonon Transport and Anomalous Diffusion | ||||||
| Abstract: Heat conduction is an important energy transport process in nature. Phonon is the major energy carrier for heat in semiconductors and dielectric materials. In analogy to Ohm’s law of electrical conduction, Fourier’s law is the fundamental law of heat conduction in solids. Although Fourier’s law has received great success in describing macroscopic heat conduction in the past two hundred years, its validity in low dimensional systems is still an open question. Here we give a brief review of the recent developments in experimental, theoretical and nu-merical studies of heat conduction in low dimensional systems, including lattice models and low dimensional nanostructures such as nanowires, nanotubes and graphene. We will demon-strate that phonons transport in low dimensional systems superdiffusively, which leads to a size dependent thermal conductivity. In other words, Fourier’s law is not applicable in low dimensional structures. | ||||||
| Author: M. I. Hussein | Category: Org. Colloquium | |||||
| Affiliation: University of Colorado Boulder | ||||||
| Paper #: 0177 | Time: 12:20 pm -12:40 pm | |||||
| Title: Thermal Conductivity Reduction by Nanophononic Metamaterials | ||||||
| Abstract: We present the concept of a locally resonant nanophononic metamaterial for the purpose of thermal conductivity reduction and utilization as a thermoelectric material system. The proposed configuration consists of a silicon thin-film with a periodic array of pillars erected on its free surface(s). This configuration qualitatively alters the base thin-film phonon spectrum due to a hybridization mechanism between the pillar local resonances and the underlying lattice dispersion, thus causing a significant reduction in the thermal conductivity. | ||||||
| Author: E. Abdel-Rahman | Category: Guest Lecture on Thermoacoustics | |||||
| Affiliation: The American University in Cairo | ||||||
| Paper #: N/A | Time: 12:40 pm -1:00 pm | |||||
| Title: TBA | ||||||
| Abstract: TBA | ||||||
| Lunch Break (Kahramana Resturant) | 1:00 pm - 3:30 pm | |||||
| Bloch Lecture | ||||||
| Session: 9 (Amaraua Conference Hall) | 3:30 pm - 4:15 pm | |||||
| Session Chair: I. El-Kady | ||||||
| Author: B. Djafari-Rouhani | Category: Award Lecture | |||||
| Affiliation: Université Lille 1 Sciences et Technologies | ||||||
| Paper #: Bloch-Paper | Time: 3:30 pm -4:15 pm | |||||
| Title: Optomechanical interactions in phoxonic cavities | ||||||
| Abstract: Phoxonic crystals can exhibit dual phononic/photonic band gaps. Therefore, the confinement of both acoustic and optical waves in a phoxonic cavity can allow the enhancement of their interaction. In this paper, we discuss some of our recent theoretical works on the strength of the optomechanic coupling, based on both photoelastic and moving interfaces mechanisms, in different (2D, slabs, strips) phoxonic crystals cavities. | ||||||
| Track 3: Phonon Transport | ||||||
| Session: 10 (Amaraua Conference Hall) | 4:15 pm - 6:30 pm | |||||
| Session Chair: I. J. Maasilta | ||||||
| Author: M. Y. Swinkels | Category: Contributed Oral | |||||
| Affiliation: Eindhoven University of Technology | ||||||
| Paper #: 0072 | Time: 4:15 pm -4:30 pm | |||||
| Title: Investigation of Phonon Transport in Nanowires for Thermoelectric Applications | ||||||
| Abstract: Nanowires could be interesting candidates for future thermoelectric materials thanks to the reduced phonon transport in these wires. A full understanding of phonon transport in these small scales is required to take full advantage of this. In this work we will present an approach for investigations on the thermoelectric properties of nanowires. | ||||||
| Author: T. A. Puurtinen | Category: Contributed Oral | |||||
| Affiliation: University of Jyväskylä | ||||||
| Paper #: 0026 | Time: 4:30 pm -4:45 pm | |||||
| Title: Ballistic Heat Transfer in Thin-Film Phononic Crystals | ||||||
| Abstract: We have measured the thermal transport properties of various thin-film phononic crystals in the sub-Kelvin temperature range using sensitive normal-metal-insulator-superconductor (NIS) tunnel junction thermometry. We have also compared the measurements to numerical results of a ballistic phonon radiation model implemented by the finite element method, and found good agreement. | ||||||
| Author: K. Sääskilahti | Category: Contributed Oral | |||||
| Affiliation: Aalto University | ||||||
| Paper #: 0066 | Time: 4:45 pm -5:00 pm | |||||
| Title: Quantum Heat Transfer in Graphene Nanostructures: Self-Consistent Thermal Bath Calculation | ||||||
| Abstract: We present an extended Green’s function method to study phonon heat transfer and apply the method to graphene point contacts. Phonon damping and dephasing are introduced by coupling all atoms to Langevin heat baths, whose temperatures are determined self-consistently. We calculate temperature profiles for various geometries and discuss the im-portance of quantum effects at different temperatures. | ||||||
| Author: P. E. Hopkins | Category: Contributed Oral | |||||
| Affiliation: University of Virginia | ||||||
| Paper #: 0052 | Time: 5:00 pm -5:15 pm | |||||
| Title: Einstein Oscillations and Exceptionally Low Thermal Conductivities of Fullerene Derivative PCBM | ||||||
| Abstract: We report on the thermal conductivities of microcrystalline [6,6]-phenyl C61-butyric acid methyl ester (PCBM) thin films from 135 to 387 K as measured by time domain thermoreflectance. Thermal conductivities are independent of temperature above 180 K and less than 0:030+/-0:003 W m-1 K-1 at room temperature. The longitudinal sound speed is determined via picosecond acoustics and is found to be 30% lower than that in C60/C70 fullerite compacts. Using Einstein’s model of thermal conductivity, we find the Einstein characteristic frequency of microcrystalline PCBM is 2.88x1012 rad s-1. By comparing our data to previous reports on C60/C70 fullerite compacts, we argue that the molecular tails on the fullerene moieties in our PCBM films are responsible for lowering both the apparent sound speeds and characteristic vibrational frequencies below those of fullerene films, thus yielding the exceptionally low observed thermal conductivities. | ||||||
| Author: R. Cheaito | Category: Contributed Oral | |||||
| Affiliation: University of Virginia | ||||||
| Paper #: 0081 | Time: 5:15 pm -5:30 pm | |||||
| Title: Experimental Evidence of Crossover from Incoherent to Coherent phonon Scattering in Epitaxial Oxide Superlattices | ||||||
| Abstract: We experimentally demonstrate the theoretically predicted crossover from incoherent to coherent phonon transport in (SrTiO3)m/(CaTiO3)m oxide superlattices by showing a local minimum in phonon thermal conductivity as a function of period spacing in these struc-tures. | ||||||
| Author: F. Döring | Category: Contributed Oral | |||||
| Affiliation: University of Göttingen | ||||||
| Paper #: 0039 | Time: 5:30 pm -5:45 pm | |||||
| Title: Interface Design for Minimizing thermal Conductivity by Phonon Blocking in Multilayers | ||||||
| Abstract: Different kinds of multilayers with small layer thicknesses and a high number of interfaces were fabricated by pulsed laser deposition. The thermal conductivities of the grown multilayers were studied using fs-pump-probe reflectivity measurements. In this contribution, the phonon spectra are discussed with respect to the possibility to obtain phonon blocking by multilayer design in order to minimize the thermal conductivity. | ||||||
| Author: A. K. Kushwaha | Category: Contributed Oral | |||||
| Affiliation: K.N. Govt. P.G. College | ||||||
| Paper #: 0027 | Time: 5:45 pm -6:00 pm | |||||
| Title: Phonon Spectrum of MnTe, HgTe and Their Mixed Semiconductor MnxHg1-xTe | ||||||
| Abstract: We have calculated the phonon spectrum of MnTe, HgTe and their mixed semiconductor MnxHg1-xTe in the framework of three-body shell model. This model incorporates the effect of the short-range repulsive interactions up to and including the second nearest neighbours, in addition to the long-range Coulombic interactions in the framework of the rigid-shell model with both the ions are polarizable. The calculated phonon spectrum for MnTe, HgTe and MnxHg1-xTe are plotted along with their available experimental results. We find an overall good agreement with the experimental results. | ||||||
| Author: J. S. Reparaz | Category: Contributed Oral | |||||
| Affiliation: Catalan Institute of Nanotechnology | ||||||
| Paper #: 0048 | Time: 6:00 pm -6:15 pm | |||||
| Title: Si and Ge Membranes Investigated through Raman Thermometry: The Role of Phonon Boundary Scattering and Phonon Confinement in 2D Systems | ||||||
| Abstract: The unique thermal properties exhibited by free-standing ultra-thin semiconductor membranes, have recently triggered a considerable amount of research in this field. A precise knowledge of the influence of low dimensionality, chemical composition, degree of crystallinity and surface roughness is essential to tailor the thermal properties of membranes. We investigate the thermal conductivity reduction in Si and Ge free-standing membranes at 300 K as function of thickness, ranging from 6 to 700 nm, using Raman thermometry. This contactless technique is extremely convenient for those cases where electrical techniques are not easily applicable. We show that the thermal conductivity systematically decreases as the membranes thickness decrease, which we show to originate from boundary scattering at the membrane´s surfaces and phonon confinement. Reductions of the thermal conductivity of up to one order of magnitude with respect to its bulk value were observed for the thinnest membranes. Furthermore, we discuss the validity of Raman thermometry regarding experimental accuracy and we provide general guidelines to perform finite element calculations to solve the heat equation in order to extract the thermal conductivity. | ||||||
| Author: D. Schneider | Category: Contributed Oral | |||||
| Affiliation: Max Planck Institute for Polymer Research | ||||||
| Paper #: 0040 | Time: 6:15 pm -6:30 pm | |||||
| Title: 1D Hybrid Phononic Bragg-Stacks: Propagation of Hypersound in Soft Periodic Structures* | ||||||
| Abstract: Soft periodic structures constitute a promising material class to study phononic properties. Here, we focus on 1D hybrid phononic crystals as model system to study fundamentals of elastic wave propagation. Spontaneous Brillouin light scattering (BLS) in combination with theoretical calculations provide full description of phononic band diagrams at hypersonic frequencies. | ||||||
| Adjourn | 6:30 PM | |||||
| * Phononic Crystals Talk | ||||||