Understanding the physical processes involved in interfacial heat transfer is critical for the interpretation of thermometric measurements and the optimization of heat dissipation in nanoelectronic devices that are based on transition metal dichalcogenide (TMD) semiconductors. We model the phononic and electronic contributions to the thermal boundary conductance (TBC) variability for the MoS$_{2}$-SiO$_{2}$ and WS$_{2}$-SiO$_{2}$ interface. A phenomenological theory to model diffuse phonon transport at disordered interfaces is introduced and yields $G$=13.5 and 12.4 MW/K/m$^{2}$ at 300 K for the MoS$_{2}$-SiO$_{2}$ and WS$_{2}$-SiO$_{2} $ interface, respectively. We compare its predictions to those of the coherent phonon model and find that the former fits the MoS$_{2}$-SiO$_{2}$ data from experiments and simulations significantly better. Our analysis suggests that heat dissipation at the TMD-SiO$_{2}$ interface is dominated by phonons scattered diffusely by the rough interface although the electronic TBC contribution can be significant even at low electron densities ($n\leq10^{12}$ cm$^{-2}$) and may explain some of the variation in the experimental TBC data from the literature. The physical insights from our study can be useful for the development of thermally aware designs in TMD-based nanoelectronics.
We point out that the effective channel for the interfacial thermal conductance, the inverse of Kapitza resistance, of metal-insulator/semiconductor interfaces is governed by the electron-phonon interaction mediated by the surface states allowed in a thin region near the interface. Our detailed calculations demonstrate that the interfacial thermal conductance across Pb/Pt/Al/Au-diamond interfaces are only slightly different among these metals, and reproduce well the experimental results of the interfacial thermal conductance across metal-diamond interfaces observed by Stoner et al. [Phys. Rev.…
Energy dispersion and spin orientation of the protected states at interfaces between topological insulators (TIs) and non-topological materials depend on the charge redistribution, strain, and atomic displacement at the interface. Knowledge of these properties is essential for applications of topological compounds, but direct access to them in the interface geometry is difficult. We show that conductance of a gated double junction at the surface of a topological insulator exhibits oscillations and a quasi-linear decay as a function of gate voltage in different regimes. These give the values fo…
Thermal conductance across bonded SiOx-SiOx interfaces in hybrid bonding process
School of Integrated Circuits and Beijing Advanced Innovation Center for Integrated Circuits, Peking University（北京大学集成电路学院与北京集成电路先进创新中心）；School of Integrated Circuits, Southeast University（东南大学集成电路学院）
We report experimental and computational studies of thermal transport properties in hexagonal boron nitride (hBN) encapsulated molybdenum disulfide (MoS2) structure using refined optothermal Raman techniques, and reveal very high interfacial thermal conductance between hBN and MoS2. By studying the Raman shift of hBN and MoS2 in suspended and substrate-supported thin films under varying laser power and temperature, we calibrate lateral (in-plane) thermal conductivity of hBN and MoS2 and the vertical interfacial thermal conductance in the hBN/MoS2/hBN heterostructure as well as the interfaces b…
Ferromagnetic materials exhibiting low magnetic damping ($α$) and moderately high saturation magnetization are required from the viewpoints of generation, transmission and detection of spin wave. Since spin-to-charge conversion efficiency is another important parameter, high spin mixing conductance ($g_{r}^{\uparrow \downarrow}$) is the key for efficient spin-to-charge conversion. Full Heusler alloys e.g. $Co_2Fe_{0.4}Mn_{0.6}Si$ (CFMS), which are predicted to be 100$\%$ spin polarized, possess low $α$. However, the $g_{r}^{\uparrow \downarrow}$ at the interface between CFMS and a paramagnet h…
The effective spin-mixing conductance (G_eff) of a heavy metal/ferromagnet (HM/FM) interface characterizes the efficiency of the interfacial spin transport.Accurately determining G_eff is critical to the quantitative understanding of measurements of direct and inverse spin Hall effects. G_eff is typically ascertained from the inverse dependence of magnetic damping on the FM thickness under the assumption that spin pumping is the dominant mechanism affecting this dependence.Here we report that, this assumption fails badly in many in-plane magnetized prototypical HM/FM systems in the nm-scale th…
By way of the nonequilibrium Green's function simulations and first principles calculations, we report that borophene, a single layer of boron atoms that was fabricated recently, possesses an extraordinarily high lattice thermal conductance in the ballistic transport regime, which even exceeds graphene. In addition to the obvious reasons of light mass and strong bonding of boron atoms, the superior thermal conductance is mainly rooted in its strong structural anisotropy and unusual phonon transmission. For low-frequency phonons, the phonon transmission within borophene is nearly isotropic, sim…
Motivated by recent experiments, we study the variability of the thermal conductance of single dithiolated alkane molecules of varying length connecting two gold electrodes. For this purpose, we examine (i) the influence of the metal-molecule contact and of the electrode orientation on the thermal conductance of straight alkane chains, (ii) the effect of molecule-internal disorder realized through torsional gauche defects and the behavior upon stretching, and (iii) the modifications resulting from temperature-dependent dynamical variations of the geometry. While we analyze the former two aspec…
Understanding the properties of electronic transport across metal-molecule interfaces is of central importance for controlling a large variety of molecular-based devices such as organic light emitting diodes, nanoscale organic spin-valves and single-molecule switches. One of the primary experimental methods to reveal the mechanisms behind electronic transport through metal-molecule interfaces is the study of conductance as a function of molecule length in molecular junctions. Previous studies focused on transport governed either by tunneling or hopping, both at low conductance. However, the up…
The acoustic mismatch model and the diffuse mismatch model have been widely used to predict the thermal interface conductance. However, the acoustic mismatch model (diffuse mismatch model) is based on the hypothesis of a perfectly smooth (completely disordered) interface. Here, we present a new modified model, named as the mixed mismatch model, which considers the roughness/bonding at the interface. By taking partially specular and partially diffuse transmissions into account, the mixed mismatch model can predict the thermal interface conductance with arbitrary roughness. The proportions of sp…
We report a study on spin conductance in ultra-thin films of Yttrium Iron Garnet (YIG), where spin transport is provided by propagating spin waves, that are generated and detected by direct and inverse spin Hall effects in two Pt wires deposited on top. While at low current the spin conductance is dominated by transport of thermal magnons, at high current, the spin conductance is dominated by low-damping non-equilibrium magnons thermalized near the spectral bottom by magnon-magnon interaction, with consequent a sensitivity to the applied magnetic field and a longer decay length. This picture i…
The traditional atomistic Green's function (AGF) was formulated in the harmonic regime, preventing it from capturing the role of anharmonicity in interfacial thermal transport. Incorporating anharmonicity into AGF has long been desired but remains challenging. We developed a rigorous anharmonic AGF model to incorporate anharmonicity at interfaces in 3-D structures with first-principles force constants. Thermal conductance of silicon- and aluminum-based interfaces is significantly enhanced resulting from the new channels opened by inelastic scattering. This work represents a major step forward …
Thermoelectric conductance of an edge mode is investigated. The edge modes of a $2D $ and $3D$ two band model with parabolic dispersion is considered. For the the one dimensional non interacting fermions the thermal conductivity computed agrees with the result known from $Bosonization$ computations. In the presence of a magnetic field, backscattering is allowed and controls the value of the thermal conductivity. The thermal conductivity is obtained from the continuity equation of thermal current energy conservation. The thermal conductivity is computed introducing the $Scattering$ matrix for p…
Periodic hole array phononic crystals (PnC) can strongly modify the phonon dispersion relations, and have been shown to influence thermal conductance coherently, especially at low temperatures where scattering is suppressed. One very important parameter influencing this effect is the period of the structure. Here, we measured the sub-Kelvin thermal conductance of nanofabricated PnCs with identical hole filling factors, but three different periodicities, 4, 8, and 16 $μ$m, using superconducting tunnel junction thermometry. We found that all the measured samples can suppress thermal conductance …
Quantized thermal conductance of dielectric quantum wires
利用输运理论的Landauer公式，我们预测介电量子线在低温下应该表现出量子化的热导，在弹道声子制度。热传导的量子是通用的，与材料的特性无关，并且等于$π^2 k^2_B T /3h$，其中$k_B$是玻耳兹曼常量，h是普朗克常数，T是温度。量子化的热导应该是实验上可观察到的悬浮纳米结构，磁耦合到水库，设备，可以实现在目前的时间。
Thermoelectric conductance of Dirac materials and in particular zero modes reveals the effect of topology .Weyl semimetals with a boundary at z = 0 give rise to chiral zero modes with- out backscattering resulting in a significant contribution to thermal conductivity. By doping the surface with paramagnetic impurities backscattering is allowed, and the thermal conductivity is controlled by the decrease of the transmission function |t|^{2} < 1. We attach a thermal reservoir at the edge of the sample and study the thermal and electrical conductance. For the ballistic and mesoscopic situations, q…
Motivated by recent experiments [Science 355, 6330 (2017); Nat. Nanotechnol. 12, 430 (2017)], we present here an extensive theoretical analysis of the thermal conductance of atomic-size contacts made of three different metals, namely gold (Au), platinum (Pt) and aluminum (Al).
Despite the importance of high thermal conductance (i.e. low thermal resistance) of metal contacts to thermal management of graphene devices, prior reported thermal conductance of metal/graphene interfaces are all relatively low, only 20-40 MW m$^{-2}$ K$^{-1}$. One possible route to improve the thermal conductance ($G$) of metal/graphene interfaces is through additional heat conduction by electrons, since graphene can be easily doped by metals. In this paper, we evaluate the electronic heat conduction across metal/graphene interfaces by measuring the thermal conductance of Pd/transferred grap…
Influence of electrical properties on thermal boundary conductance at metal/semiconductor interface
Université de Reims Champagne-Ardennes（兰斯香槟-阿登大学）；INSA de Lyon（里昂国立应用科学学院）；Univ. Lille, CNRS, Univ. Polytechnique Hauts-de-France, Junia（里尔大学、法国国家科学研究中心、上法兰西理工学院、朱尼亚学院）；Université de Technologie de Troyes（特鲁瓦技术大学）；University of Pittsburgh（匹兹堡大学）；Université Claude Bernard Lyon 1-CNRS（里昂第一大学-法国国家科学研究中心）
The universal quantization of thermal conductance provides information on the topological order of a state beyond electrical conductance. Such measurements have become possible only recently, and have discovered, in particular, that the value of the observed thermal conductance of the 5/2 state is not consistent with either the Pfaffian or the anti-Pfaffian model, motivating several theoretical articles. The analysis of the experiments has been made complicated by the presence of counter-propagating edge channels arising from edge reconstruction, an inevitable consequence of separating the dop…
The interface between a ferro-/ferrimagnetic insulator and a normal metal can support spin currents polarized collinear with and perpendicular to the magnetization direction. The flow of angular momentum perpendicular to the magnetization direction ("transverse" spin current) takes place via spin torque and spin pumping. The flow of angular momentum collinear with the magnetization ("longitudinal" spin current) requires the excitation of magnons. In this article we extend the existing theory of longitudinal spin transport [Bender and Tserkovnyak, Phys. Rev. B 91, 140402(R) (2015)] in the zero-…
A semi-analytical model for studying thermal transport at the nanoscale, able to accurately describe both the effect of out of equilibrium transport and the thermal transfer at interfaces, is presented. Our approach is based on the definition of pseudo local temperatures distinguishing the phonon populations according to the direction of their velocity. This formalism leads to a complete set of equations capturing the heat transfer in nanostructures even in the case of hetero-structures. This model only requires introducing a new intrinsic thermal parameter called ballistic thermal conductance…
We determine the thermal conductance of thin niobium (Nb) wires on a silica substrate in the temperature range of 0.1 - 0.6 K using electron thermometry based on normal metal-insulator-superconductor tunnel junctions. We find that at 0.6 K, the thermal conductance of Nb is two orders of magnitude lower than that of Al in the superconducting state, and two orders of magnitude below the Wiedemann-Franz conductance calculated with the normal state resistance of the wire. The measured thermal conductance exceeds the prediction of the Bardeen-Cooper-Schrieffer theory, and demonstrates a power law d…
We study the role of anharmonicity at interfaces with an added intermediate layer designed to facilitate interfacial phonon transport. Our results demonstrate that while in the harmonic limit the bridge may lower the conductance due to fewer available channels, anharmonicity can strongly enhance the thermal conductance of the bridged structure due to added inelastic channels. Moreover, we show that the effect of anharmonicity on the conductance can be tuned by varying temperature or the bridge layer thickness, as both parameters change the total rate of occurrence of phonon-phonon scattering p…
