The effect of preferential wetting of one of the constituent block chains and corresponding block copolymer morphologies to a carbon substrate is studied from a molecular level. The single chain distribution of the bl...
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We use cathodoluminescence (CL) mapping and Kelvin probe force microscopy (KFM) to investigate fluctuations of the InN mole fraction in InGaN films grown by radio-frequency plasma-assisted molecular beam epitaxy. Both...
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Ordered structures of Ba(Cd1/3Ta2/3)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-or...
Ordered structures of Ba(Cd1/3Ta2/3)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba(Cd1/3Ta2/3)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size ∼18 nm) and high-density domain boundaries induced by ordering were observed for Ba(Cd1/3Ta2/3)O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba(Cd1/3Ta2/3)O3 ceramics.
We have investigated the nucleation and growth of gallium nitride (GaN) films on silicon and sapphire substrates using halide vapor phase epitaxy (HVPE). GaN growth was carried out on bare Si and sapphire surfaces, as...
We have investigated the nucleation and growth of gallium nitride (GaN) films on silicon and sapphire substrates using halide vapor phase epitaxy (HVPE). GaN growth was carried out on bare Si and sapphire surfaces, as well as on MOVPE-grown GaN buffer layers. HVPE growth on MOVPE GaN/AIN buffer layers results in lower defect densities as determined by x-ray than growth directly on sapphire. HVPE GaN films grown directly on sapphire exhibit strong near-edge photoluminescence, a pronounced lack of deep level-based luminescence, and x-ray FWHM values of 16 arcsec by an x-ray θ-2θ scan. The crystallinity of GaN films on sapphire is dominated by the presence of rotational misorientation domains, as measured by x-ray ω-scan diffractometry, which tend to decrease with increasing thickness or with the use of a homoepitaxial MOVPE buffer layer. The effect of increasing film thickness on the defect density of the epilayer was studied. In contrast, the HVPE growth of nitride films directly on silicon is complicated by mechanisms involving the formation of silicon nitrides and oxides at the initial growth front.
In this study, we investigated the effects of DNA/Pt-DNA strands as hole collecting layers in polymer heterojunction solar cells based on ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al structure. We demonstrated that by introducing D...
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We fabricated a number of top-gate graphene field-effect transistors on the ultrananocrystalline diamond (UNCD) – Si composite substrates. Raman spectroscopy, scanning electron microscopy and atomic force microscopy ...
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We fabricated a number of top-gate graphene field-effect transistors on the ultrananocrystalline diamond (UNCD) – Si composite substrates. Raman spectroscopy, scanning electron microscopy and atomic force microscopy were used to verify the quality of UNCD and graphene device channels. The thermal measurements were carried out with the “hot disk” and “laser flash” methods. It was found that graphene on UNCD devices have increased breakdown current density by ~50% compared to the reference devices fabricated on Si/SiO2. The relatively smooth surface of UNCD, as compared to other synthetic diamond films, allowed us to fabricate top gate graphene devices with the drift mobility of up to ~ 2587 cm2V−1s−1.
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
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