作者：
Balandin, Alexander A.Nano-Device Laboratory
Department of Electrical Engineering and Materials Science and Engineering Program University of California - Riverside Riverside CA 92521 United States
Superior thermal properties of graphene are described and its prospective applications in thermal management are discussed. Studies have shown that the thermal conductivity of graphene depend on the size of the flakes...
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Superior thermal properties of graphene are described and its prospective applications in thermal management are discussed. Studies have shown that the thermal conductivity of graphene depend on the size of the flakes and edge roughness. To evaluate the possible enhancement with graphene fillers, the effective medium approximation (EMA) approach is used, modifying it to incorporate the thermal boundary resistance (TBR). It is found that the effective thermal conductivity decreases with decreasing diameter of carbon nanotubes (CNT), and that the graphene-based thermal interface materials (TIM) show stronger effective thermal conductivity compared to those with CNTs. An experimental study found a 1000% enhancement for graphene-epoxy composite and 500% enhancement for graphene-silver epoxy composite at 5.0 vol% fraction.
The effect of surface passivation and crystallite size on the photoluminescence of porous silicon is reported. Oxygen-free porous silicon samples with medium to ultra high porosities have been prepared by using electr...
The effect of surface passivation and crystallite size on the photoluminescence of porous silicon is reported. Oxygen-free porous silicon samples with medium to ultra high porosities have been prepared by using electrochemical etching followed by photoassisted stain etching. As long as the samples were hydrogen-passivated the PL could be tuned from the red (750nm) to the blue (400nm) by increasing the porosity. We show that when surface oxidation occurred, the photoluminescence was red-shifted. For sizes smaller than 2.8nm, the red shift can be as large as 1eV but for larger sizes no shift has been observed. Comparing the experimental results with theoretical calculations, we suggest that the decrease in PL energy upon exposure to oxygen is related to recombination involving an electron or an exciton trapped in Si=O double bonds. This result clarifies the recombination mechanisms in porous silicon.
作者：
Liming DaiDong Wook ChangJong-Beom BaekWen LuCenter of Advanced Science and Engineering for Carbon (Case4Carbon)
Department of Macromolecular Science and Engineering Case Western Reserve University 10900 Euclid Avenue Cleveland OH 44106 USA Wen Lu
EnerG2 Inc. 100 NE Northlake Way Suite 300 Seattle WA 98105 USA. Interdisciplinary School of Green Energy
Institute of Advanced Materials & Devices Ulsan National Institute of Science and Technology (UNIST) 100 Banyeon Ulsan 689-798 South Korea EnerG2
Inc. 100 NE Northlake Way Suite 300 Seattle WA 98105 USA Liming Dai
Center of Advanced Science and Engineering for Carbon (Case4Carbon) Department of Macromolecular Science and Engineering Case Western Reserve University 10900 Euclid Avenue Cleveland OH 44106 USA
The spontaneous alignment of molecules in liquid crystalline solutions is characteristic of other materials that contain rodlike particles. We are developing a model to predict the evolution of microstructure in these...
The spontaneous alignment of molecules in liquid crystalline solutions is characteristic of other materials that contain rodlike particles. We are developing a model to predict the evolution of microstructure in these systems. Its starting point is Flory’s thermodynamic analysis of liquid crystalline phase separation. Our preferred method dispenses with the traditional lattice model in favor of a Monte Carlo simulation to calculate entropy. Some advantages and consequences of our approach are explored in this paper
The morphology of nanocrystalline (nc)-Si/amorphous (a)-SiO2 superlattices (SLs) is studied using Raman spectroscopy in the acoustic and optical phonon ranges, transmission electron microscopy (TEM), and atomic force ...
The morphology of nanocrystalline (nc)-Si/amorphous (a)-SiO2 superlattices (SLs) is studied using Raman spectroscopy in the acoustic and optical phonon ranges, transmission electron microscopy (TEM), and atomic force microscopy (AFM). It is demonstrated that high temperature annealing (up to 1100°C) and oxidation in O2/H2O ambient do not destroy the SL structure, which retains its original periodicity and nc-Si/a-SiO2 interface abruptness. It is found that oxidation at high temperatures reduces the defect density in nc-Si/a-SiO2 SLs and induces the lateral coalescence of Si nanocrystals (NCs). The size, shape, packing density, and crystallographic orientation of the Si nanocrystals are studied as a function of the oxidation time.
Experiments with monolayers of macroscopic rods indicate separation into isotropic and aligned phases at greater-than-critical concentrations. This behavior is qualitatively similar to that of rodlike liquid crystalli...
Experiments with monolayers of macroscopic rods indicate separation into isotropic and aligned phases at greater-than-critical concentrations. This behavior is qualitatively similar to that of rodlike liquid crystalline polymers, which in turn has been modelled successfully in threedimensions by Flory and Ronca. We have adapted their approach to predict the ordering of rods in two dimensions. A preliminary phase diagram is presented. The critical rod concentration at which an aligned phase can appear first is a decreasing function of rod axial ratio. Rods of a given axial ratio will phase separate at lower overall concentrations in two dimensions than in three.
Inorganic polymers are used in the formation of green compacts via sedimentation of colloidal alumina suspended in chloroform. Polymers containing highly polar components tend to produce constant density profiles of g...
Inorganic polymers are used in the formation of green compacts via sedimentation of colloidal alumina suspended in chloroform. Polymers containing highly polar components tend to produce constant density profiles of greater than 55% density, while those containing nonpolar, reactive components produce profiles with a large gradient in packing density. Density profiles describing the sedimentation behavior versus time and the final dried density of the compacts are generated via the use of gamma-ray densitometry. These polymers have the potential not only to increase green compact density but also to reduce weight losses due to “burnout” and subsequent sintering requirements by pyrolyzing to a ceramic phase.
Large area graphene film is usually grown on a metal and then transferred to a substrate for its utilization. We report here a rapid (10 seconds) graphene growth method that can be carried out on any desired substrate...
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Large area graphene film is usually grown on a metal and then transferred to a substrate for its utilization. We report here a rapid (10 seconds) graphene growth method that can be carried out on any desired substrate, including insulator, thus negating the need for the transfer. This method is based on metal-induced crystallization of amorphous carbon to graphene, and involves a very thin metal layer that is less than 10 nm thick. Rapid thermal annealing of a bilayer of a-C and metal deposited on a given surface leads to the formation of graphene film, and subsequent breaking-up of the thin metal layer underneath the film, resulting in a graphene-metal hybrid that can be used as a transparent electrode. Post annealing, which causes agglomeration of nano-crystallites, enhances transmittance of the film without affecting sheet resistance. The nature of the growth method allows not only large area formation of graphene film but also film formation only on desired area.
We report the enhanced interface properties between passivation layers and InSb by using remote PECVD system. SiO2 and Si3N4 layers deposited by remote PECVD showed lower interface trap densities than layers deposited...
We report the enhanced interface properties between passivation layers and InSb by using remote PECVD system. SiO2 and Si3N4 layers deposited by remote PECVD showed lower interface trap densities than layers deposited by normal PECVD. SiO2 layers deposited by remote PECVD showed 7.1×1011 cm−2 eV−1 of interface trap density at midgap which is slightly lower than SiO2 layers deposited by PECVD. Si3N4 layers deposited by remote PECVD showed 1.6∼1.7×1012 cm−2 eV−1 at midgap which is 3 times lower than Si3N4 layers deposited by PECVD. Interface properties of SiO2 are superior to that of Si3N4 in both case of PECVD and remote PECVD. To investigate the interface properties between SiO2 and InSb, X‐ray photoelectron spectroscopy was conducted. Indium and antimony oxide phases were found at the interface and these oxide phases could act as the origin of interface traps.
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