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During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m−1 K−1, while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field., YF, JH, YL, AZ, MK and JL acknowledge the financial support from The Swedish National Science Foundation (VR under the contract No 621-2007-4660), The Swedish Foundation for Strategic Research (SSF) under contract (No SE13-0061), the Swedish Board for innovation under the Siografen program and from the Production Area of Advance at Chalmers University of Technology, Sweden. SC, YZ and JL acknowledge the financial support by the Key R&D Development Program from the Ministry of Science and Technology of China with the contract No: 2017YFB040600 and the National Natural Science Foundation of China (No. 51872182). XX is supported the National Natural Science Foundation of China (No. 11674245 & No. 11890703). MS and CMST acknowledge financial support from the CERCA programme/Generalitat de Catalunya, the Severo Ochoa Centres of Excellence programme, funded by the Spanish Research Agency (AEI, Grant No. SEV-2017-0706).

As feature density increases within microelectronics, so does the dissipated power density, which puts an increased demand on thermal management. Thermal interface materials (TIMs) are used at the interface between contacting surfaces to reduce the thermal resistance, and is a critical component within many electronics systems. Arrays of carbon nanotubes (CNTs) have gained significant interest for application as TIMs, due to the high thermal conductivity, no internal thermal contact resistances and an excellent conformability. While studies show excellent thermal performance, there has to date been no investigation into the reliability of CNT array TIMs. In this study, CNT array TIMs bonded with polymer to close a Si-Cu interface were subjected to thermal cycling. Thermal interface resistance measurements showed a large degradation of the thermal performance of the interface within the first 100 cycles. More detailed thermal investigation of the interface components showed that the connection between CNTs and catalyst substrate degrades during thermal cycling even in the absence of thermal expansion mismatch, and the nature of this degradation was further analyzed using X-ray photoelectron spectroscopy. This study indicates that the reliability will be an important consideration for further development and commercialization of CNT array TIMs.

High anisotropic thermal materials, which allow heat to dissipate in a preferential direction, are of interest as a prospective material for electronics as an effective thermal management solution for hot spots. However, due to their preferential heat propagation in the in-plane direction, the heat spreads laterally instead of vertically. This limitation makes these materials ineffective as the density of hot spots increases. Here, we produce a new dielectric thin film material at room temperature, named vertically ordered nanocrystalline h-BN (voBN). It is produced such that its preferential thermally conductive direction is aligned in the vertical axis, which facilitates direct thermal extraction, thereby addressing the increasing challenge of thermal crosstalk. The uniqueness of voBN comes from its h-BN nanocrystals where all their basal planes are aligned in the direction normal to the substrate plane. Using the 3ω method, we show that voBN exhibits high anisotropic thermal conductivity (TC) with a 16-fold difference between through-film TC and in-plane TC (respectively 4.26 and 0.26 W·m–1·K–1). Molecular dynamics simulations also concurred with the experimental data, showing that the origin of this anisotropic behavior is due to the nature of voBN’s plane ordering. While the consistent vertical ordering provides an uninterrupted and preferred propagation path for phonons in the through-film direction, discontinuity in the lateral direction leads to a reduced in-plane TC. In addition, we also use COMSOL to simulate how the dielectric and thermal properties of voBN enable an increase in hot spot density up to 295% compared with SiO2, without any temperature increase. MOE (Min. of Education, S’pore) Accepted version

This paper concerns the thermal properties of graphene-based films for heat spreading applications. Following liquid phase exfoliation (LPE) films were made by two different methods, vacuum filtration and drop coating. Temperature decreases of up to 6 °C and 4 °C were measured at a heat flux density of 1200 W/cm2 for the vacuum filtrated and drop coated films respectively. For the first time in this paper, three different methods were combined to evaluate and predict the thermal performance of such graphene-based films. Resistance thermometers were used to monitor the hotspot temperature decrease versus the Joule heat flow as a result of using graphene-based heat spreaders. The 3ω method was used to experimentally determine the in-plane and through-plane thermal conductivities of such films. A finite element model of the hotspot test structure was setup using the in-plane and through-plane thermal conductivities (110 and 0.25 W/mK, respectively) obtained from the 3ω measurements. Simulations were performed to predict the hotspot temperature decrease with excellent agreement obtained between all methods. The results indicate that the alignment and purity of the graphene-based films, as well as their thermal boundary resistance with respect to the chip, are key parameters when determining the thermal performance of graphene-based heat spreaders.

Carbon nanotubes (CNTs) are long considered as a promising material for thermal applications. However, problems such as low volume CNT fraction abhorrent to practical applications have been raising the demand for novel architecture of this material. Here we demonstrate two fabrication methods, in which a self-assembly method for fabricating covalent-bonded CNT network (3D CNT) and another method for covalent-bonded C to CNTs (C@CNT) network, and presented both as a potential method to enhance thermal conductivity of CNT arrays. We utilized pulsed photothermal reflectance technique and using new four-layer heat conduction model based on the transmission-line theory to measure thermal conductivity of the samples. The 3D CNT with thermal conductivity of 21 W mK−1 and C@CNT with thermal conductivity of 26 W mK−1 turn out to be an excellent candidate for thermal interface material as the thermal conductivity increased by 40% and 70% respectively as compared to conventional CNT arrays. The improvement is attributed to the efficient thermal routines constructed between CNTs and secondary CNTs in 3D CNT and between C layer and CNTs in C@CNT. The other factor to improve thermal conductivity of the samples is decreasing air volume fraction in CNT arrays. Our fabrication methods provide a simple method but effective way to fabricate 3D CNT and C@CNT and extend the possibility of CNTs towards TIM application. Ministry of Education (MOE) Published version We thank for the financial support from the Swedish Foundation for Strategic Research (SSF) under contract (No SE13–0061), Swedish National Board for Innovation (Vinnova)Graphene SIO-Agenda Program, Formas program on graphene enhanced composite as well as from the Production Area of Advance at Chalmers University of Technology, Sweden. Thanks are also given to the Ministry of Science and Technology of China with the contract No: 2017YFB040600 for the financial support. This research benefited also from the support of the Ministry of Education (Singapore) under the grant MOE2014-T2-2-105.

Following Moores law, the development of electronics has led to an exponential increase of transistor density over the last couple of decades. Unfortunately, this trend also gives an increased heat power density in active components. Thermal interface materials (TIMs) are used to decrease the thermal resistance in thermal packages by filling out air gaps that naturally form there. TIMs are at the same time identified as a bottleneck due to their relatively low thermal conductivity. Carbon nanotubes (CNTs) are proposed as a future material for TIMs due to their high thermal conductivity and conformable nature. However, no reliability studies for CNT array TIMs can be found in literature that would demonstrate how these types of interfaces would perform. This is to the authors best knowledge the first reported study on thermal reliability for a CNT array TIM, which will be an important step towards a market realisation.

Thermal-crosstalk has become a prominent issue in modern electronic. Here, we present a new type of vertically-ordered Boron Nitride (voBN) thin films to address such limitation. voBN has a high anisotropic thermal conductivity with 16 times difference between through-plane and in-plane and can be deposited in room temperature. We studied the thermal properties with 3\omega method and verified with COMSOL Multiphysics simulations. Such characteristic would allow hotspot density to increase by 295%.

In the joint project SMARTHERM the applicability of vertically-aligned carbon nanotubes (VA CNT) is main subject of interest. Target is the implementation of a VACNT layer as functional thermal interface material into an RF package to prove this promising technology's feasibility. This paper presents the approach the SMARTHERM consortium has taken so far. Beginning with a general motivation why to engage in this topic, the approach and the chosen demonstrator design are introduced. One focus lies on the description of the demonstrator and its components alongside with a comprehensive view into the assembling as main challenge. The choice of measurement techniques is discussed and the measures of success are defined. Finally, the results are presented, discussed and concluded and an outlook is provided how the findings influence further approaches in the project.

As a three-dimensional porous structure made of two-dimensional graphene building blocks, graphene foam, has gained enormous attention in recent years. Such graphene foam integrates graphene sheets into macroscopic structures meanwhile inheriting most of the fascinating intrinsic properties of graphene. Together with its ultralow density, high porosity and flexibility, graphene foam has been proposed in many applications, such as supercapacitors, microwave shielding, electrochemical sensing and lithium-ion batteries. In this paper, three-dimensional graphene foams were synthesized by low pressure chemical vapor deposition. The obtained graphene foams were characterized by scanning electron microscopy and Raman spectroscopy. The results show that nickel foam surface was fully covered by graphene. The Raman spectra show that most graphene were multilayer, but monolayer and bilayer graphene were also found in some areas. In addition to this, it was also found that the synthesized graphene has very small D peak, indicating high quality of the synthesized graphene.

In this work a Cu paste consisting in both micro and nanoparticles was produced. The copper paste was produced with different additive weight percentages of Ag coated SiC and sintered for 30min at 500°C under 6,5MPa in N 2 atmosphere. The thermal resistance and composition of the resulting joints was studied. XPS and EDX measurements show no significant oxidation of the Cu after sintering, which is attributed to the combination of reductive agents in the paste and the inert atmosphere. SEM images of cross sections show contacts with no voids between the SiC particles and the copper matrix. Thermal conductivity measurements with laser flash analysis (LFA) show that the additive increases the effective thermal conductivity to more than double of that of the pure copper paste at 2% additive weight percentage, but bigger amounts yield smaller improvements and presumably would eventually worsen it.

Graphene and CNT have great potential in electronics applications. This work explored the possibility of integrating 1D CNT and 2D graphene into a 3D covalently bonded structure, i.e. a graphene-CNT hybrid material for thermal management application. The graphene-CNT hybrid material was later investigated morphologically and thermally to observe its heat dissipation capability.

We demonstrate the thermal conductivity enhancement of the vertically aligned carbon nanotube (CNT) arrays (from ∼15.5 to 29.5 W/mK, ∼90% increase) by encapsulating outer boron nitride nanotube (BNNT, 0.97 nm-thick with ∼3–4 walls). The heat transfer enhancement mechanism of the coaxial C@BNNT was further revealed by molecular dynamics simulations. Because of their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT. This work provides deep insights into tailoring the heat transfer of arbitrary CNT arrays and will enable their broader applications as thermal interface material. MOE (Min. of Education, S’pore)

Thermal transport in graphene with one type of grain boundary loop was investigated using non-equilibrium molecular dynamics simulation method. The results showed that thermal conductivity is very sensitive to defect concentration. It rapidly decreases in the presence of a defect. This is attributed the phonon defects scattering which shorten the phonon mean free paths leading to the reduction in thermal conductivity. Furthermore, temperature dependency of thermal conductivity of pristine and defected graphene was determined. The results indicated that thermal conductivity of defect-free graphene varies significantly with temperature, while thermal conductivity of graphene with defect remains nearly invariant with the temperature of the system. This implies the possibility of phonon-defect scattering domination over Umklapp phonon–phonon scattering in graphene with defect.

A series of physical vapour deposition titanium aluminum silicon nitride nanocomposite coating with a different (Al + Si)/Ti atomic ratio, with a thickness of around 2.5 μm were deposited on stainless steel substrate by a lateral rotating cathode arc process in a flowing nitrogen atmosphere. The composition and microstructure of the as-deposited coatings were analyzed by energy dispersive X-ray spectroscopy, and X-ray diffraction, and cross-sectional scanning electron microscopy observation. The titanium nitride (TiN) coating shows a clear columnar structure with a predominant (111) preferential orientation. With the incorporation of Al and Si, the crystallite size in the coatings decreased gradually, and the columnar structure and (111) preferred orientation disappeared. Thermal conductivity of the as-deposited coating samples at room temperature was measured by using pulsed photothermal reflectance technique. Thermal conductivity of the pure TiN coating is about 11.9 W/mK. With increasing the (Al + Si)/Ti atomic ratio, the coatings' thermal conductivity decreased monotonously. This reduction of thermal conductivity could be ascribed to the variation of coatings' microstructure, including the decrease of grain size and the resultant increase of grain boundaries, the disruption of columnar structure, and the reduced preferential orientation.

The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by ∼28 °C for a chip operating at 1,300 W cm−2. Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene–graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime., The high thermal conductivity of graphene is considerably reduced when the two-dimensional material is in contact with a substrate. Here, the authors show that thermal management of a micro heater is improved using graphene-based films covalently bonded by amino-silane molecules to graphene oxide.

The effect of nanocrystals with preferred orientation on the thermal conductivity of carbon films is studied. During graphitization, the presence of biaxial compressive stress results in the formation of preferred orientation in the microstructure of graphitic nanocrystals if the corresponding activation energy is supplied. This formation of preferred orientation leads to the orientation of graphitic basal planes perpendicular to the substrate. Due to the high thermal conductivity of graphite in the basal planes, there is a significant increase in thermal conductivity of textured nanocrystalline films compared to amorphous film.

CrAlN and TiAlN coatings were deposited on stainless steel substrates by a lateral rotating cathode arc technique. The composition and structure of the as-deposited coatings were analyzed by energy dispersive analysis of X-rays (EDX) and X-ray diffraction (XRD). Thermal conductivity of these coatings is measured using pulsed photothermal reflectance (PPR) technique at room temperature. The measured thermal conductivity of pure TiN coating is around 11.9 W/mK. With increasing Al content, thermal conductivity of the TiAlN coatings decreased significantly and a minimum value of about 4.63 W/mK was obtained at the Al/Ti atomic ratio around 0.72. With the increase of Al content, thermal conductivity of CrAlN coatings decreased slightly but consistently. The variation of thermal conductivity in these coatings is explained in term of phonon scattering on grain boundaries and local strain centers caused by lattice distortion. In comparison with TiAlN, thermal conductivity of CrAlN coatings was evidently lower, which could be partially responsible for their better performance in high speed machining applications as observed in our previous work.

In the present work, we have measured thermal-conductivity of industrial thin film TiAlN with a thickness of around 3 μm. These films are used in machining industry for cutting tools in order to increase their service life. A series of TiAlN coating with a different Al/Ti atomic ratio were deposited on Fe-304 stainless steel (AISI304) substrate by a lateral rotating cathode arc process. The samples were then coated with a 0.8 μm gold layer on top by magnetron sputtering. We present the thermal-conductivity measurement of these samples using pulsed photothermal reflectance (PPR) technique at room temperature. The thermal conductivity of the pure TiN coating is about 11.9 W/mK. A significant decrease in thermal conductivity was found with increasing Al/Ti atomic ratio. A minimum thermal conductivity of about 4.63 W/mK was obtained at the Al/Ti atomic ratio of around 0.72.

Due to substantial phonon scattering induced by various structural defects, the in-plane thermal conductivity (K) of graphene films (GFs) is still inferior to the commercial pyrolytic graphite sheet (PGS). Here, the problem is solved by engineering the structures of GFs in the aspects of grain size, film alignment, and thickness, and interlayer binding energy. The maximum K of GFs reaches to 3200 W m−1K−1and outperforms PGS by 60%. The superior K of GFs is strongly related to its large and intact grains, which are over four times larger than the best PGS. The large smooth features about 11 µm and good layer alignment of GFs also benefit on reducing phonon scattering induced by wrinkles/defects. In addition, the presence of substantial turbostratic-stacking graphene is found up to 37% in thin GFs. The lacking of order in turbostratic-stacking graphene leads to very weak interlayer binding energy, which can significantly decrease the phonon interfacial scattering. The GFs also demonstrate excellent flexibility and high tensile strength, which is about three times higher than PGS. Therefore, GFs with optimized structures and properties show great potentials in thermal management of form-factor-driven electronics and other high-power-driven systems.

Graphene and carbon nanotubes have received much attention for thermal management application due to their unique thermal performance. Theoretical work suggests that a covalent bond can combine 1D carbon nanotubes with 2D graphene together to extend the excellent thermal property to three dimensions for heat dissipation. This paper experimentally demonstrates the high heat dissipation capability of a freestanding 3D multiwall carbon nanotube (MWCNT) and graphene hybrid material. Using high-resolution transmission electron microscopy and pulsed photothermal reflection measurement method, the covalent bonds between MWCNT and planar graphene are microscopically and numerically demonstrated. Thermal resistance at the junction with covalent bonds is 9×10^−10 Kelvin square meter per watt, which is three orders of magnitude lower than van der Waals contact. Joule heating method is used to verify the extra cooling effect of this 3D hybrid material compared to graphite film. A demonstrator using high power chip is developed to demonstrate the applicability of this hybrid material in thermal application. Temperature at hot spots can be decreased by around 10°C with the assistance of this hybrid material. These findings are very significant for understanding the thermal conduction during combining 1D and 2D carbon material together for future thermal management application.

Nanostructured thermoelectric semiconductors represent a promising new direction that can further increase energy conversion efficiency, which requires the realization of thermoelectric nanocrystals with size comparable to their de Broglie wavelength while maintaining a high electrical conductivity. Here, we demonstrate a new facile process to grow self-assembled Sb2Te3 nanoparticles with controlled particle size and enhanced thermoelectric properties by using a catalyst-free vapor transport growth technique. The samples show much more enhanced Seebeck coefficients than that of bulk Sb2Te3 with similar charge carrier concentration. Meanwhile, the thermal conductivity measurements with pulse photothermal reflectance suggest that the these Sb2Te3 nanoparticle films show much reduced thermal conductivity as compared to that of bulk Sb2Te3. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.

A series of [TiN/TiAlN](n) multilayer coatings with different bilayer numbers n=5, 10, 25, 50, and 100 were deposited on stainless steel substrate AISI 304 by a lateral rotating cathode arc technique in a flowing nitrogen atmosphere. The composition and microstructure of the coatings have been analyzed by using energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), and conventional and high-resolution transmission electron microscopy (HRTEM). XRD analysis shows that the preferential orientation growth along the (111) direction is reduced in the multilayer coatings. TEM analysis reveals that the grain size of the coatings decreases with increasing bilayer number. HRTEM imaging of the multilayer coatings shows a high density misfit dislocation between the TiN and TiAlN layers. The cross-plane thermal conductivity of the coatings was measured by a pulsed photothermal reflectance technique. With increasing bilayer number, the multilayer coatings' thermal conductivity decreases gradually. This reduction of thermal conductivity can be ascribed to increased phonon scattering due to the disruption of columnar structure, reduced preferential orientation, decreased grain size of the coatings and present misfit dislocations at the interfaces. (C) 2015 Elsevier B.V. All rights reserved.

To develop optically-controlled resistive memories, we study the laser-induced graphitization and amorphization of vertically oriented nano-crystalline graphite (vnC-G) thin films deposited with the filtered cathodic vacuum arc method. vnc-G films consist in graphitic planes perpendicular to the substrate within a matrix of amorphous carbon [1]. Controlled graphitization and amorphization of carbon materials is a long-standing issue with unclear mechanisms [2-5]. Here, we report on graphitization and amorphization of vnc-G controlled by single 532 nm-5 ns laser pulses of various intensities. We demonstrate partial reversibility between graphitization and amorphization, opening the way toward device applications. Depending on pulse energy, samples also display an intricate typology of degradations, from periodic ripples, cracks, upheavals and spheroids to traces of explosions. Supported by a finite-element thermo-mechanical model, we discuss the impact of the orientation of the graphitic planes.

In this dissertation, the experimental investigation of the heat transport in crystalline nanostructured materials is studied. Different methods to reduce their thermal conductivity to create user-specific materials are presented as well. It is shown that by using different methods such as the incorporation of additional elements in the crystalline structure, controlling the deposition and embedding metallic nanoinclusions in the semiconductor matrix, it is possible to reduce the thermal conductivity. Thermal conductivity measurements have been conducted by using pulsed photothermal reflectance (PPR) and 3ω techniques at room temperature. The materials studied in this work include Ti-based hard coatings, multilayer TiN/TiAlN coatings and n-type Bi2Te2.7Se0.3 thermoelectric films. Firstly, the effect of the incorporation of Al on the thermal conductivity of TiAlN coatings prepared by a lateral rotating cathode arc (LARC) technique has been investigated. To study this, a series of TiAlN coatings were deposited on stainless steel substrates and the thermal conductivity of the coatings was measured by the PPR technique. The Microstructure of the coatings was analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These techniques reveal that TiN coating shows a clear columnar structure with a predominant (111) preferential orientation. With the incorporation of Al, the columnar structure of the coatings is disrupted, the grain size of the coatings is decreased and the dislocation density is increased. A significant decrease in thermal conductivity was found with increasing Al content and a minimum thermal conductivity of about 4.63 W/mK was obtained at the Al/Ti atomic ratio of around 0.72. The decrease in thermal conductivity of the TiAlN coatings is explained in terms of increased phonon scattering due to the decrease in the grain size and increasing dislocation density. The effect of the incorporation of Al and Si on the thermal conductivity of the TiAlSiN nanocomposite coatings prepared by the LARC technique has been studied. A series of TiAlSiN nanocomposite coatings were deposited on stainless steel substrates and the room temperature thermal conductivity of the coatings was measured by the PPR technique. A significant decrease in thermal conductivity was found with increasing Al and Si contents and it was shown that the thermal conductivity of the TiAlSiN nanocomposite coatings is about 1.8 W/mK at a (Al+Si)/Ti atomic ratio of around 1.76. The decrease in thermal conductivity of the TiAlSiN nanocomposite coatings can be attributed to the reduced grain size and the formation of a nanocomposite structure which consists of crystalline nanograins embedded in a disordered, lower thermal conductivity than TiAlN, amorphous SiNx matrix. In order to study the effect of a multilayer structure on the thermal conductivity, a series of multilayer [TiN/TiAlN]n coatings with different bilayer numbers n were deposited on stainless steel substrates by the LARC technique. The PPR technique was employed to measure thermal conductivity of the coatings at room temperature. TEM observation and microstructure analysis of multilayer coatings show a lattice mismatch and misfit dislocations at the interfaces between TiN and TiAlN layers, and a decrease of the grain size with increasing number of layers. Results show that the thermal conductivity of the multilayer coatings reduces with increasing bilayer number n. Phonon scattering is increased at the interfaces and grain boundaries due to the existence of misfit dislocations and to the decreasing grain size, respectively. For the study of the effect of metallic nanoinclusions in thermoelectric (TE) film on the thermal conductivity, textured n-type Bi2Te2.7Se0.3 thin films with Pt nanoinclusions were successfully prepared via pulsed laser deposition. The thermal conductivity of the TE films was measured by the 3ω technique. The TEM observation shows that the Pt nanoinclusions are embedded at the grain boundaries of the semiconductor matrix. By introducing Pt nanoinclusions, the thermal conductivity is reduced due to scattering phonon at the grain boundaries. ELECTRICAL and ELECTRONIC ENGINEERING

Non-equilibrium molecular dynamic simulation was employed to investigate the interfacial thermal conductance between diamond and silicon substrate. The interfacial thermal conductance was computed based on Fourier's law. The simulation was done at different temperature ranges and results show that the interfacial thermal conductance between diamond-silicon is proportional to temperature and increases with temperature even above Debye temperature of silicon. Enhancement of thermal boundary conductance with temperature is attributed to inelastic phonon-phonon scattering at the interface. The system size dependence of interfacial thermal conductance was also examined. We found that thermal transport is a function of the system size when the size of system is smaller than the phonon mean free path and increases with the size of structure. We also simulated the effect of interface defect on phonon scattering and subsequently thermal conductance. The results also show that interface defect enhances acoustic phonon scattering which results in reduction of thermal boundary conductance. Our findings provide accurate and valuable information on phonon transport in diamond-silicon structure. Published version

Thermal conductivity of individual multiwalled carbon nanotubes (MWCNT) is measured using a pulsed photothermal reflectance technique. Intrinsic thermal conductivity of individual MWCNT with a diam- eter 150 nm and length 2 mm at room temperature is extracted to be 2586 W/mK. Individual MWCNT is surrounded by SiO2, so parallel resistor model is applied in which SiO2 supportive is treated as a con- ducting channel that transports heat in parallel with MWCNT.

In order to meet the demands of increasing package density and miniaturization of devices without compromising performance, the most challenging issues to tackle are thermal and interconnect management. In this paper, we will first understand the interfacial transport between Si and Carbon for better system integration and discuss how novel carbon films can be used for thermal extraction. Second, we will show how carbon nanotubes can be used as interconnects using a flip chip approach as well as potential radio frequency applications.

Thermal boundary conductance at the interface of diamond-amorphous carbon has been calculated using non-equilibrium molecular dynamic simulation. In particular, we describe the effect of solid stiffness, which associated with sp3 hybridization ratio of amorphous carbon, on thermal boundary conductance. The result shows that by increasing the sp3 hybridization ratio of amorphous carbon, thermal boundary conductance between diamond and amorphous carbon increases.

A rapid solidification and high throughput melt spinning process is developed for the fabrication of new Sn–Ge alloys as anodes for high capacity lithium-ion batteries. Compared to pure micron-sized Sn and Ge, the alloy possesses enhanced lithium storage properties. High, reversible and stable capacities of over 1000 mA h g−1 are maintained over 60 cycles at 0.1 C. A good rate capability of 500 mA h g−1 at 5 C is also achieved, making it very attractive for very fast charge/discharge applications. More remarkably, it has a tap density of 2.05 g cm−3 and thus high volumetric capacities of 2050 mA h cm−3 at 0.1 C and 1025 mA h cm−3 at 5 C. The electrode was investigated via ex situ XRD, EXAFS and TEM at various cut-off voltages during the first cycle and after the first cycle to establish the structure–property relationship. The Sn–Ge alloy is observed to undergo a transformation from the crystalline Sn–Ge alloy into phase separated nanocrystalline Sn in an amorphous Ge matrix. The excellent lithium storage properties exhibited by Sn–Ge are attributed to the synergistic effect between the phases and the phase transformation occurred.