| 61. |
- Li, Haohao, et al.
(författare)
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Chemical Vapor Deposition of Vertically Aligned Carbon Nanotube Arrays: Critical Effects of Oxide Buffer Layers
- 2019
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Ingår i: Nanoscale Research Letters. - : Springer Science and Business Media LLC. - 1556-276X .- 1931-7573. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Vertically aligned carbon nanotubes (VACNTs) were synthesized on different oxide buffer layers using chemical vapor deposition (CVD). The growth of the VACNTs was mainly determined by three factors: the Ostwald ripening of catalyst nanoparticles, subsurface diffusion of Fe, and their activation energy for nucleation and initial growth. The surface roughness of buffer layers largely influenced the diameter and density of catalyst nanoparticles after annealing, which apparently affected the lifetime of the nanoparticles and the thickness of the prepared VACNTs. In addition, the growth of the VACNTs was also affected by the deposition temperature, and the lifetime of the catalyst nanoparticles apparently decreased when the deposition temperature was greater than 600 °C due to their serious Ostwald ripening. Furthermore, in addition to the number of catalyst nanoparticles, the density of the VACNTs was also largely dependent on their activation energy for nucleation and initial growth.
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| 62. |
- Li, Qi, 1990, et al.
(författare)
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Compact and low loss electrochemical capacitors using a graphite / carbon nanotube hybrid material for miniaturized systems
- 2019
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 412, s. 374-383
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Tidskriftsartikel (refereegranskat)abstract
- With the establishment of the internet of things (IoT) and the rapid development of advanced microsystems, there is a growing demand to develop electrochemical capacitors (ECs) to replace bulky electrolytic capacitors on circuit boards for AC line filtering, and as a storage unit in energy autonomous systems. For this purpose, ECs must be capable of handling sufficiently high signal frequencies, display minimum energy loss through self-discharge and leakage current as well as maintaining an adequate capacitance. Here, we demonstrate ECs based on mechanically flexible, covalently bonded graphite/vertically aligned carbon nanotubes (graphite/VACNTs) hybrid materials. The ECs employing a KOH electrolyte exhibit a phase angle of −84.8°, an areal capacitance of 1.38 mF cm−2 and a volumetric capacitance (device level) of 345 mF cm−3 at 120 Hz, which is among the highest values for carbon based high frequency ECs. Additionally, the performance as a storage EC for miniaturized systems is evaluated. We demonstrate capacitive charging/discharging at μA current with a gel electrolyte, and sub-μA leakage current reached within 50 s, and 100 nA level equilibrium leakage within 100 s at 2.0 V floating with an ionic liquid electrolyte.
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| 63. |
- Lin, Rui, et al.
(författare)
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Real-time 100 Gbps/lambda/core NRZ and EDB IM/DD Transmission over 10 km Multicore Fiber
- 2018
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Ingår i: 2018 Optical Fiber Communications Conference and Exposition (OFC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781943580385 ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- A BiCMOS chip-based real-time IM/DD spatial division multiplexing system is experimentally demonstrated for short-reach communications. 100 Gbps/λ/core NRZ and EDB transmission is achieved below 7%-overhead HD-FEC limit after 10km 7-core fiber with optical dispersion compensation.
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| 64. |
- Lin, Rui, et al.
(författare)
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Real-time 100 Gbps/λ/core NRZ and EDB IM/DD transmission over multicore fiber for intra-datacenter communication networks
- 2018
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Ingår i: Optics Express. - : OSA - The Optical Society. - 1094-4087. ; 26:8, s. 10519-10526
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Tidskriftsartikel (refereegranskat)abstract
- A BiCMOS chip-based real-time intensity modulation/direct detection spatial division multiplexing system is experimentally demonstrated for both optical interconnects. 100 Gbps/λ/core electrical duobinary (EDB) transmission over 1 km 7-core multicore fiber (MCF) is carried out, achieving KP4 forward error correction (FEC) limit (BER < 2E-4). Using optical dispersion compensation, 7 × 100 Gbps/λ/core transmission of both non-return-to-zero (NRZ) and EDB signals over 10 km MCF transmission is achieved with BER lower than 7% overhead hard-decision FEC limit (BER < 3.8E-3). The integrated low complexity transceiver IC and analog signal processing approach make such a system highly attractive for the high-speed intra-datacenter interconnects..
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| 65. |
- Lin, Rui, et al.
(författare)
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Spatial division multiplexing for optical data center networks
- 2018
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Ingår i: 22ND INTERNATIONAL CONFERENCE ON OPTICAL NETWORK DESIGN AND MODELING (ONDM 2018). - : IEEE. ; , s. 239-241
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Konferensbidrag (refereegranskat)abstract
- Emerging mobile and cloud applications drive ever-increasing capacity demands, particularly for short-reach optical communications, where low-cost and low-power solutions are highly required. Spatial division multiplexing (SDM) techniques provide a promising way to scale up the lane count per fiber, while reducing the number of fiber connections and patch cords, and hence simplifying cabling complexity. This talk will address challenges on both system and network levels, and report our recent development on SDM techniques for optical data center networks.
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| 66. |
- Liu, Johan, 1960, et al.
(författare)
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Carbon Nanotubes for thermal management of Microsystems
- 2018
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Ingår i: Nanopackaging: Nanotechnologies and Electronics Packaging, Second Edition. - Cham : Springer International Publishing. ; , s. 775-791
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- One important function of electronics packaging is to remove the heat generated by the integrated circuits (ICs). Efficient cooling requires both high heat conduction within the package and efficient heat removal from the package. Elevated temperature is damaging to the chip and its package. Material mismatch causes mechanical stress leading to fatigue, creep, and finally failure; interconnects can melt, and electromigration within the IC is speeded up. Efficient heat removal is not always the case. Plastics is a common packaging material as it is electrically insulating and cheap. The thermal conductivity is, however low, about 0.2 W/mK compared to that of metals (aluminum 220 W/mK and copper 400 W/mK). Other important factors are the heat spreading and thermal interface materials. The components are often mounted on a polymer board which is only cooled by air. The heat transfer coefficient is only 5–15 W/m2 K for natural convection and 15–250 W/m2 K for forced convection in gases [1].
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| 67. |
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| 68. |
- Long, Xu, et al.
(författare)
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Finite Element Analysis to the Constitutive Behavior of Sintered Silver Nanoparticles Under Nanoindentation
- 2018
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Ingår i: International Journal of Applied Mechanics. - 1758-8251 .- 1758-826X. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Finite element (FE) simulation is adopted as a fundamental tool to evaluate the mechanical reliability of packaging structures for electronic devices. Nevertheless, the determination of mechanical properties of sintered silver nanoparticles (AgNP) remains challenging as the traditional tensile test is difficult to be performed at a limited size. In the current study, spherical nanoindentation is utilized to measure the applied load-penetration depth responses of sintered AgNP reinforced by SiC microparticles at various weight ratios (0.0, 0.5, 1.0 and 1.5 wt.%). To describe the elasto-plastic behavior of this heterogeneous material, FE analysis is performed to simulate the indentation behavior and determine the parameters in the modified power-law model by fitting the average applied load-penetration depth responses. To overcome the uniqueness problem, the Young's modulus is directly determined by continuous stiffness measurement technique and the proposed constitutive model can provide a reasonably accurate mechanical estimation of sintered AgNP. The effect of SiC content on sintered AgNP is discussed by correlating the morphology observed by scanning electron microscope (SEM) and the constitutive parameters obtained from the FE simulations.
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| 69. |
- Long, Xu, et al.
(författare)
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Mechanical behaviour of sintered silver nanoparticles reinforced by SiC microparticles
- 2019
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 744, s. 406-414
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Tidskriftsartikel (refereegranskat)abstract
- SiC microparticles with various weight ratios (0.0, 0.5, 1.0 and 1.5 wt%) are incorporated into sintered silver nanoparticles (AgNP) as one of the promising packaging materials for high-power electronic devices. Mechanical properties and constitutive behaviour of sintered AgNP reinforced by SiC microparticles are investigated based on nanoindentation experiment and analytical approach. Nanoindentations were performed in the manner of continuous stiffness measurement for a maximum penetration depth of 2000 nm at a strain rate of 0.05 s−1. Particularly, a Berkovich indenter is utilized to evaluate the values of Young's modulus and hardness, and a spherical indenter is utilized to describe the constitutive behaviour. For sintered AgNP with 0.5 wt% SiC, the morphology exhibits uniformly compact microstructures to enable optimizing the heat conductivity, the yield strength and hardening capacity of sintered AgNP material is enhanced. To describe the constitutive behaviour, an analytical approach is proposed to simulate the indentation behaviour. The parameters in the modified power-law model are determined by fitting the average indentation responses. The developed correlation between microstructure and macroscopic properties facilitates the design of AgNP paste morphology and improves the mechanical properties of sintered AgNP in electronics packaging.
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| 70. |
- Lu, Xiuzhen, et al.
(författare)
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The influence of sintering process on thermal properties of nano-silver paste
- 2018
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Ingår i: 2018 19TH INTERNATIONAL CONFERENCE ON ELECTRONIC PACKAGING TECHNOLOGY (ICEPT). - 9781538663868 - 9781538663868 ; , s. 1157-1160
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Konferensbidrag (refereegranskat)abstract
- Nano-silver paste with low sintering temperature and high operation temperature was introduced to the application of bonding materials for GaN and SiC devices. Thermal properties are critical issues for die attach materials due to the heat dissipation requirements of high power devices. The influence of sintering process parameters for nano-silver paste on the thermal properties was investigated. The thermal conductivity of sintered nano-silver paste increased with the increase of sintering temperature and sintering time because of the dense structure due to high temperature and long sintering time. To improve the thermal property, Ag coated micro-SiC particles were used as an alternative to partly replace pure nano-Ag particles. The results demonstrate that the SiC particles can reduce the voids and improve the density of the sintered silver structure. Moreover, the addition of SiC particles can also contribute to the increase of thermal diffusivity. As a result, the thermal conductivity of sintered silver paste with 1.5 wt.% Ag coated SiC particles was two times as compared to that without SiC particles with the same Ag concentration.
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