The Experts below are selected from a list of 18894 Experts worldwide ranked by ideXlab platform
Sebastian Volz - One of the best experts on this subject based on the ideXlab platform.
-
High Surface Phonon-Polariton in-Plane Thermal Conductance along Coupled Films
Nanomaterials, 2020Co-Authors: Saeko Tachikawa, Sebastian Volz, Roman Anufriev, Jose Ordonez-miranda, Laurent Jalabert, Masahiro NomuraAbstract:Surface phonon-polaritons (SPhPs) are evanescent electromagnetic waves that can propagate distances orders of magnitude longer than the typical mean free paths of phonons and electrons. Therefore, they are expected to be powerful heat carriers capable of significantly enhancing the in-plane Thermal Conductance of polar nanostructures. In this work, we show that a SiO 2 /Si (10 µm thick)/SiO 2 layered structure efficiently enhances the SPhP heat transport, such that its in-plane Thermal Conductance is ten times higher than the corresponding one of a single SiO 2 film, due to the coupling of SPhPs propagating along both of its polar SiO 2 nanolayers. The obtained results thus show that the proposed three-layer structure can outperform the in-plane Thermal performance of a single suspended film while improving significantly its mechanical stability.
-
carbon nitride 2d nanostructures Thermal conductivity and interfacial Thermal Conductance with the silica substrate
Physical Chemistry Chemical Physics, 2019Co-Authors: Ali Rajabpour, Sebastian Volz, Saeed BazrafshanAbstract:The rate of heat dissipation from a 2D nanostructure strongly depends on the interfacial Thermal Conductance with its substrate. In this paper, the interfacial Thermal Conductance of carbon-nitride 2D nanostructures (C3N, C2N, C3N4's) with silica substrates was investigated using transient molecular dynamics simulations. It was found that a 2D nanostructure with higher Thermal conductivity, has a lower value of interfacial Thermal Conductance with the silica substrate. The Thermal conductivity of suspended carbon-nitride 2D nanostructures was also calculated using the Green–Kubo formalism and compared with that of graphene as a reference structure. It was found that the Thermal conductivities of C3N, C2N, C3N4 (s-triazine) and C3N4 (tri-triazine) are respectively 62%, 4%, 4% and 2% that of graphene; while their interfacial Thermal Conductances with silica are 113%, 171%, 212% and 188% that of graphene. These different behaviors of the Thermal conductivity and the interfacial Thermal Conductance with the substrate may be important in the Thermal management of carbon-nitride 2D nanostructures in nanoelectronics.
-
Phonon interference and Thermal Conductance reduction in atomic-scale metamaterials
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2014Co-Authors: Haoxue Han, G. Lyudmila, A. Alexandre, Sebastian Volz, Yuriy A. KosevichAbstract:We introduce and model a three-dimensional (3D) atomic-scale phononic metamaterial producing two-path phonon interference antiresonances to control the heat flux spectrum. We show that a crystal plane partially embedded with defect-atom arrays can completely reflect phonons at the frequency prescribed by masses and interaction forces. We emphasize the predominant role of the second phonon path and destructive interference in the origin of the total phonon reflection and Thermal Conductance reduction in comparison with the Fano-resonance concept. The random defect distribution in the plane and the anharmonicity of atom bonds do not deteriorate the antiresonance. The width of the antiresonance dip can provide a measure of the coherence length of the phonon wave packet. All our conclusions are confirmed both by analytical studies of the equivalent quasi-1D lattice models and by numerical molecular dynamics simulations of realistic 3D lattices.
-
quantized Thermal Conductance of nanowires at room temperature due to zenneck surface phonon polaritons
Physical Review Letters, 2014Co-Authors: Jose Ordonezmiranda, Laurent Tranchant, Beomjoon Kim, Yann Chalopin, Thomas Antoni, Sebastian VolzAbstract:Based on the Landauer formalism, we demonstrate that the Thermal Conductance due to the propagation of Zenneck surface-phonon polaritons along a polar nanowire is independent of the material characteristics and is given by ${\ensuremath{\pi}}^{2}{k}_{B}^{2}T/3h$. The giant propagation length of these energy carriers establishes that this quantization holds not only for a temperature much smaller than 1 K, as is the case for electrons and phonons, but also for temperatures comparable to room temperature, which can significantly facilitate its observation and application in the Thermal management of nanoscale electronics and photonics.
Masahiro Nomura - One of the best experts on this subject based on the ideXlab platform.
-
High Surface Phonon-Polariton in-Plane Thermal Conductance along Coupled Films
Nanomaterials, 2020Co-Authors: Saeko Tachikawa, Sebastian Volz, Roman Anufriev, Jose Ordonez-miranda, Laurent Jalabert, Masahiro NomuraAbstract:Surface phonon-polaritons (SPhPs) are evanescent electromagnetic waves that can propagate distances orders of magnitude longer than the typical mean free paths of phonons and electrons. Therefore, they are expected to be powerful heat carriers capable of significantly enhancing the in-plane Thermal Conductance of polar nanostructures. In this work, we show that a SiO 2 /Si (10 µm thick)/SiO 2 layered structure efficiently enhances the SPhP heat transport, such that its in-plane Thermal Conductance is ten times higher than the corresponding one of a single SiO 2 film, due to the coupling of SPhPs propagating along both of its polar SiO 2 nanolayers. The obtained results thus show that the proposed three-layer structure can outperform the in-plane Thermal performance of a single suspended film while improving significantly its mechanical stability.
-
reduction of Thermal Conductance by coherent phonon scattering in two dimensional phononic crystals of different lattice types
Physical Review B, 2016Co-Authors: Roma Anufriev, Masahiro NomuraAbstract: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. Increases in the period and porosity of the phononic crystal affect the group velocity and phonon density of states and, as a consequence, reduce the in-plane Thermal Conductance of the structure as compared to the unpatterned membrane. This reduction does not depend significantly on the lattice type and thickness of phononic crystals. Moreover, the reduction is strongly temperature dependent and strengthens as the temperature is increased.
-
Thermal Conductance boost in phononic crystal nanostructures
Physical Review B, 2015Co-Authors: Roman Anufriev, Masahiro NomuraAbstract:A theoretical study of coherent phonon scattering in thin-film phononic-crystal nanostructures (also called thermocrystals) is presented. It is commonly assumed that phononic crystals may only reduce Thermal conductivity of materials. In this theoretical paper, contrary to this assumption, we demonstrate that phononic nanopatterning can enhance the Thermal Conductance of thin films under certain conditions. That is to say, it is shown that a thin membrane with many holes can have a higher Thermal Conductance than an unpatterned membrane. This effect originates from the increase in the density of states due to the coherent modifications of phonon dispersion. This counterintuitive phenomenon, called the Thermal Conductance boost effect, can be used for applications involving phonon management.
-
Thermal Conductance of silicon interfaces directly bonded by room temperature surface activation
Applied Physics Letters, 2015Co-Authors: Masanori Sakata, Masahiro Nomura, Takafumi Oyake, Jeremie Maire, Eiji Higurashi, Junichiro ShiomiAbstract:Using the recently developed method to directly measure Thermal boundary Conductance (TBC) across bonded interfaces, we report the measurements of TBC at interfaces bonded by surface activated bonding at room temperature. The TBC of as-bonded silicon-silicon interface is limited to 1.3 × 102 MW m−2 K−1, which is equivalent to Thermal Conductance of micrometer-thick bulk silicon. We further show that the TBC can be greatly improved by recrystallizing the amorphous interlayer, which here is realized by Thermal annealing. The dependence of the TBC on the annealing temperature is highly nonlinear, which can be explained in terms of Thermal activation of crystal growth.
Arunava Majumdar - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Conductance and thermopower of an individual single wall carbon nanotube
Nano Letters, 2005Co-Authors: Li Shi, Zhen Yao, Arunava MajumdarAbstract:We have observed experimentally that the Thermal Conductance of a 2.76-μm-long individual suspended single-wall carbon nanotube (SWCNT) was very close to the calculated ballistic Thermal Conductance of a 1-nm-diameter SWCNT without showing signatures of phonon−phonon Umklapp scattering for temperatures between 110 and 300 K. Although the observed thermopower of the SWCNT can be attributed to a linear diffusion contribution and a constant phonon drag effect, there could be an additional contact effect.
David G Cahill - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Conductance of metal diamond interfaces at high pressure
Nature Communications, 2015Co-Authors: Gregory T Hohensee, Richard Wilson, David G CahillAbstract:The Thermal Conductance of interfaces between metals and diamond, which has a comparatively high Debye temperature, is often greater than can be accounted for by two-phonon processes. The high pressures achievable in a diamond anvil cell (DAC) can significantly extend the metal phonon density of states to higher frequencies, and can also suppress extrinsic effects by greatly stiffening interface bonding. Here we report time-domain thermoreflectance measurements of metal-diamond interface Thermal Conductance up to 50 GPa in the DAC for Pb, Au0.95Pd0.05, Pt and Al films deposited on type 1A natural [100] and type 2A synthetic [110] diamond anvils. In all cases, the Thermal Conductances increase weakly or saturate to similar values at high pressure. Our results suggest that anharmonic Conductance at metal-diamond interfaces is controlled by partial transmission processes, where a diamond phonon that inelastically scatters at the interface absorbs or emits a metal phonon.
-
interfacial Thermal Conductance of transfer printed metal films
Advanced Materials, 2011Co-Authors: Seok Kim, David G Cahill, John A Rogers, Sanjiv SinhaAbstract:IO N Deterministic assembly of microdevices by transfer-printing is an advanced manufacturing technology that enables the heterogeneous integration of disparate materials on largearea substrates.[1–5] All active electronic devices generate heat as a byproduct of their operation and Thermal management of transfer-printed assemblies must be a consideration whenever the heat flux is large. While the Thermal conductivities of most materials used in microelectronics are well known, the Thermal Conductance of interfaces formed by transfer-printing is unknown. We report studies of the Thermal Conductance of interfaces formed by transfer-printing of Au and Au(Pd) alloy thin films, 100 μm × 100 μm in area and 100 nm thick, on amorphous SiO2 , hydrogen-terminated Si(001), and singlecrystal Al2O3 substrates. We find that the Thermal Conductance Gt of transfer-printed interfaces spans a relatively small range, 10 10 kW cm−2. The Thermal Conductance G of interfaces formed by physical vapor deposition of metal films on dielectric substrates has been studied extensively. G is the transport coefficient that relates the heat flux JQ to the temperature drop ΔT at an interface, JQ = GT . The observed values span a large range, from a low Conductance of G ≈ 10 MWm−2K−1 for Bi deposited on hydrogen-terminated diamond[6] to a high Conductance[7] of G ≈ 700 MWm−2K−1 for epitaxial TiN/MgO. Often,
-
pressure tuning of the Thermal Conductance of weak interfaces
Physical Review B, 2011Co-Authors: Wenpin Hsieh, Pawel Keblinski, Eric Pop, Austin S Lyons, David G CahillAbstract:We use high pressure to reveal the dependence of interfacial heat transport on the stiffness of interfacial bonds. The combination of time-domain thermoreflectance and SiC anvil techniques is used to measure the pressure-dependent Thermal Conductance $G$($P$) of clean and modified Al/SiC interfaces at pressures as high as $P$ $=$ 12 GPa. We create low-stiffness, van der Waals--bonded interfaces by transferring a monolayer of graphene onto the SiC surface before depositing the Al film. For such weak interfaces, $G$($P$) initially increases approximately linearly with $P$. At high pressures, $P$ g 8 GPa, the Thermal Conductance of these weak interfaces approaches the high values characteristic of strongly bonded, clean interfaces.
-
interfacial Thermal Conductance in spun cast polymer films and polymer brushes
Applied Physics Letters, 2010Co-Authors: Mark D Losego, David G Cahill, Lionel C H Moh, Kevin A Arpin, Paul V BraunAbstract:Interfaces between inorganic materials and anharmonic polymers have potentially intriguing Thermal transport behavior. The low Thermal conductivity of amorphous polymers limits significant interfacial effects to polymer film thicknesses of only a few nanometers. We use time-domain thermoreflectance to directly measure interfacial effects in the Thermal Conductance of spun-cast poly(methyl methacrylate) (PMMA) thin films and PMMA brushes “grafted-from” the substrate. PMMA brushes are expected to have polymer chains partially aligned perpendicular to the substrate, yet only a modest increase (13%) in Thermal conductivity is observed over spun-cast layers.
-
Thermal Conductance of inas nanowire composites
Nano Letters, 2009Co-Authors: Ann I Persson, David G Cahill, Yee Kan Koh, Lars Samuelson, Heiner LinkeAbstract:The ability to measure and understand heat flow in nanowire composites is crucial for applications ranging from high-speed electronics to thermoelectrics. Here we demonstrate the measurement of the Thermal Conductance of nanowire composites consisting of regular arrays of InAs nanowires embedded in PMMA using time-domain thermoreflectance (TDTR). On the basis of a proposed model for heat flow in the composite, we can, as a consistency check, extract the Thermal conductivity Lambda of the InAs nanowires and find Lambda(NW) = 5.3 +/- 1.5 W m(-1) K(-1), in good agreement with theory and previous measurements of individual nanowires.
Li Shi - One of the best experts on this subject based on the ideXlab platform.
-
effects of basal plane Thermal conductivity and interface Thermal Conductance on the hot spot temperature in graphene electronic devices
Applied Physics Letters, 2017Co-Authors: David Choi, Nirakar Poudel, Stephen B Cronin, Li ShiAbstract:Electrostatic force microscopy and scanning Thermal microscopy are employed to investigate the electric transport and localized heating around defects introduced during transfer of graphene grown by chemical vapor deposition to an oxidized Si substrate. Numerical and analytical models are developed to explain the results based on the reported basal-plane Thermal conductivity, κ, and interfacial Thermal Conductance, G, of graphene and to investigate their effects on the peak temperature. Irrespective of the κ values, increasing G beyond 4 × 107 W m−2 K−1 can reduce the peak temperature effectively for graphene devices made on sub-10 nm thick gate dielectric, but not for the measured device made on 300-nm-thick oxide dielectric, which yields a cross-plane Thermal Conductance (Gox) much smaller than the typical G of graphene. In contrast, for typical G values reported for graphene, increasing κ from 300 W m−1 K−1 toward 3000 W m−1 K−1 is effective in reducing the hot spot temperature for the 300-nm-thick oxi...
-
Thermal Conductance and thermopower of an individual single wall carbon nanotube
Nano Letters, 2005Co-Authors: Li Shi, Zhen Yao, Arunava MajumdarAbstract:We have observed experimentally that the Thermal Conductance of a 2.76-μm-long individual suspended single-wall carbon nanotube (SWCNT) was very close to the calculated ballistic Thermal Conductance of a 1-nm-diameter SWCNT without showing signatures of phonon−phonon Umklapp scattering for temperatures between 110 and 300 K. Although the observed thermopower of the SWCNT can be attributed to a linear diffusion contribution and a constant phonon drag effect, there could be an additional contact effect.
