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Electrochromics is a key “green” technology for massive energy savings in the built environment jointly with indoor comfort. This paper surveys basic electrochromic (EC) device designs, useful oxide materials and their nanostructures, and elements of a theoretical description of the EC phenomenon. It also outlines critical manufacturing technologies and their pros and cons. Focus is on EC foil technology, which is shown capable of mass fabrication via roll-to-roll web coating and continuous lamination.
Electrophoretic displays, the rewritable non-light-emitting display technology based on the movement of colored pigments inside a low dielectric liquid as a voltage is applied, have attracted a great deal of academic and commercial interests due to the combination of the advantages of both electronic displays and conventional paper, including paper-like high contrast appearance, ultra-low power consumption, thinness, flexibility etc. Fabrication of electrophoretic ink by microencapsulating the electrophoretic suspension into individual microcapsules is one way to realize such application. However, there are still some limitations for its commercial application, such as the dispersion and the electrophoretic mobility of charged particles due to the nano-particles aggregation, the barrier property and stability of microcapsule wall due to the suspension releasing, etc. In this presentation, systematic studies on the preparation of electrophoretic particles and microencapsulation by complex coacervation method were carried out to solve the mentioned problems. The obtained microcapsules can be quasi-monolayer coated on ITO/PET substrate and driven by static mode to obtain a matrix character display prototype.
Mineralized biological materials such as nacre and bone achieve remarkablecombinations of stiffness and toughness through staggered arrangements ofstiff components bonded by softer materials. These natural composites aretherefore substantial source of inspiration for emerging syntheticmaterials. In order to gain new insights into structureperformancerelationships of these staggered structures, nacres from four species werecompared in terms of fracture toughness and damage propagation pattern.Fracture tests revealed that all nacres display rising crack resistancecurves, but to different extents. Using in-situ optical and atomic forcemicroscopy, two distinct patterns of damage propagation were identified incolumnar and sheet nacre respectively. These two different patterns werefurther confirmed by means of large scale numerical models of staggeredstructures. Similar mechanisms possibly operate at the smallest scales ofthe microstructure of bone.
High-quality InGaN/GaN multiple quantum wells (MQWs) were fabricated on nano-scale epitaxial lateral overgrown (NELO) GaN layers which was prepared using nanometer-scale SiO2 islands, with an average diameter and interdistance of 300nm and 200nm respectively, as the growth mask. The active region of the device consists of five periods of GaN/InGaN MQWs were grown on top of the NELO layer using MOCVD technique. It is observed that some of the dislocations from the undoped GaN were blocked by the SiO2 growth mask and typical threading dislocation (TD) density found in the NELO samples is ~7.5×107cm-2. Significant improvement in the electroluminescence (EL) is observed which is believed to partly arise from the improvement in the internal quantum efficiency (ηi). The experimental data on the temperature dependence of the photoluminescence (PL) were fitted to a proposed model using Levenberg-Marquardt approximation. Based on our analyses it is found that the relative improvement in ηi at 300K over a control device grown in the same growth condition but without the NELO layer to a NELO device is only 0.59. It is generally accepted that TD is the non-radiative recombination center which affects the IQE. Therefore, room-temperature IQE values also support that NELO device exhibits lower TD density.
Studies of the electronic transport properties of n-type doped hydrogenated amorphous/nanocrystalline silicon (a/nc-Si:H) films deposited in a dual-plasma co-deposition reactor are described. For these doped a/nc-Si:H, the conductivity increases monotonically for increasing crystal fractions up to 60% and displays marked deviations from a simple thermally activated temperature dependence. Analysis of the temperature dependence of the activation energy for these films finds that the dark conductivity is best described by a power-law temperature dependence, σ = σo (T/To)n where n = 1 – 4, suggesting multiphonon hopping as the main transport mechanism. These results suggest that electronic transport in mixed-phase films occurs through the a-Si:H matrix at lower nanocrystal concentrations and shifts to hopping conduction between clusters of nanocrystals at higher nanocrystal densities.
In recent years, an increase in usage of methane gas in household and automobile industry has been observed. Detection of methane is always a great cause of concern for safety at home or automobile industries, productions in mines and chemical factories. This paper reports the response characteristics of rf-sputtered SnO2 thin films (90 nm thin) loaded with nanoscale catalytic clusters for detection of methane. Ultrathin (8 nm) metal and metal-oxide catalysts (Pt, Ag, Ni, Pd, Au, NiO, Au2O3) clusters are loaded over the surface SnO2 thin film. The SnO2-Pd cluster structure is found to exhibit an enhanced response (97.2%) for 200 ppm of methane at a relatively low operating temperature (220oC). The enhanced response is shown to be primarily due to the dominant roles played by both Fermi level energy control mechanism and spillover mechanism.
The relation between chemical potential and Seebeck coefficient was investigated by using high-resolution angle resolved photoemission spectroscopy. The temperature dependence of chemical potential was experimentally determined for the n-type TiS2 thermoelectric material and compared with the measured Seebeck coefficient. We found that the temperature dependence of chemical potential of TiS2 is significantly large, and its effect on Seebeck coefficient is not negligible. This fact strongly indicates that the temperature dependence of chemical potential has to be properly understood to construct the guiding principle for developing new, practical thermoelectric materials.
Lower absorption, lower refractive index and tunable resistance are three advantages of doped silicon oxide containing nanocrystalline silicon grains (nc-SiOx) compared to doped microcrystalline silicon, for the use as p- and n-type layers in thin-film silicon solar cells. In this study we show how optical, electrical and microstructural properties of nc-SiOx layers depend on precursor gas ratios and we propose a growth model to explain the phase separation in such films into Si-rich and O-rich regions as visualized by energy-filtered transmission electron microscopy.
In this work, NiSx was deposited on FTO by chemical bath and worked as the inner layer in order to enhance the photocurrent of CdS film. It is found the unannealed CdS/NiSx had a higher photocurrent than unannealed CdS, but after annealing, the photocurrent of CdS/NiSx showed dramatical decrease. The mechanism was discussed in detail by UPS and current-potential curves.
The heterogeneous integration of III-V semiconductors with the Si platform is expected to provide high performance CMOS logic for future technology nodes because of high electron mobility and low electron effective mass in III-V semiconductors. However, there are many technology issues to be addressed for integrating III-V MOSFETs on the Si platform as follow; high-quality MOS interface formation, low resistivity source/drain formation, and high-quality III-V film formation on Si substrates. In this paper, we present several possible solutions for the above critical issues of III-V MOSFETs on the Si platform. In addition, we present the III-V CMOS photonics platform on which III-V MOSFETs and III-V photonics can be monolithically integrated for ultra-large scale electric-optic integrated circuits.
In this work we demonstrate that the application of shear to a disordered lyoptropic liquid phase formed by a biological lipid, monoolein formed in water and butanediol results in the formation of an aligned lamellar phase. Furthermore we show that if shear is applied to this disordered phase in the presence of additional water, an highly oriented inverse bicontinous cubic phase is created. We suggest that these two phase may have applications as biological models, as templates for nanostructured materials and in improved protein crystallization techniques.
In this contribution, we present an effective strategy for assembling and integrating functional, in situ formed micro- and nanosized structures. Microfluidic platforms are employed to form anisotropic hybrid structures and coordination polymers at the interface of two precursor streams. Microstamps, embedded in the microfluidic device and actuated by pressure, provide a facile and reliable technology for structure trapping, localization and integration.
This paper reports on new experimental findings and conclusions regarding the pulsed-laser-induced melting-and-solidification behavior of PECVD a-Si films. The experimental findings reveal that, within the partial-melting regime, these a-Si films can melt and solidify in ways that are distinct from, and more complex than, those encountered in microcrystalline-cluster-rich LPCVD a-Si films. Specifically (1) spatially dispersed and temporally stochastic nucleation of crystalline solids occurring relatively effectively at the moving liquid-amorphous interface, (2) very defective crystal growth that leads to the formation of fine-grained Si proceeding, at least initially after the nucleation, at a sufficiently rapidly moving crystal solidification front, and (3) the propensity for local preferential remelting of the defective regions and grain boundaries (while the beam is still on) are identified as being some of the fundamental factors that can participate and affect how these PECVD films melt and solidify.
In this work, we study glass-coated single-crystal Bi98Sb02 wires obtained by liquid phase casting.
Semimetal Bi98Sb02 nanowires exhibited a "semiconductor" behavior of the temperature dependence R(T) for wire diameters <400 nm, which is significantly higher than the critical diameter (70 nm) for similar dependences R(T) of pure bismuth nanowires. The thermopower sign reversal in the temperature dependence α(T) was found to depend on the wire diameter d. The effect is interpreted in terms of manifestation of the quantum size effect, based on the appearance a new scattering channel stimulated by fluctuations in the diameter d.
The effect of negative magnetoresistance in a perpendicular magnetic field was observed for the first time both at H | | C3 and H | | C2 in magnetic fields of 1 T.
It is shown that a semimetal-semiconductor transition can be controlled using an elastic strain and a strong magnetic field, which lead to a significant shift of the band boundaries of the energy extrema in the bands
A 100 micron fragment of a b-axis oriented single crystal Gd5Si2Ge2 has been studied using microcalorimetry, enabling the separate measurement of the heat capacity and the latent heat. The sample was taken from the same crystal previously studied with Hall probe imaging, which showed that the phase transition is seeded by a second phase of Gd5Si1.5Ge1.5 nanoplatelets on the increasing field sweep direction only. The multiple transition features observed in the latent heat signature suggests a nucleation size of approximately 20 μm, consistent with the lengthscale suggested by Hall imaging. The difference in nucleation and growth process with field sweep direction is clearly identified in the latent heat. We show that the latent heat contribution to the entropy change is of the order of 50% of the total entropy change and unlike other systems studied, the transition does not broaden (and the latent heat contribution does not diminish significantly) as magnetic field and temperature are increased within the parameter range explored in these experiments.
This paper addresses scaling issues in graphene nanoribbon transistors (GNRFETs) by using a two-dimensional (2-D) Poisson and drift-diffusion solver with finite element method (FEM). GNRFETs with the back gate control and the channel width down to less than 5nm have been reported to have Ion=Ioff ratio up to 106. Our simulations show an agreement with the published experimental work and show a potential to reach unit current gain cut-off frequency, fT , up to more than 1THz with a satisfying Ion=Ioff ratio at the same time. This makes GNRFETs attractive for high speed logic.
This paper demonstrates light-induced tuning of optical spectrum from optical microfiber knot resonator overlaid with an azobenzene-doped nematic liquid crystal (azo-doped NLC). The high-quality fiber resonator is made by drawing the single mode fiber to the micro-size diameter and self-twisting the microfiber as a knot shape. During the UV light irradiation the azobenzene molecules perform trans-to-cis photoisomerization which disrupts the NLC orientation. The disrupted NLC changes the effective refractive index within the LC overlaid fiber area and shifts the optical spectrum of microfiber knot resonator. The 0.25 nm spectral shifting of resonance wavelength was observed under the irradiation of 50 mW UV light.
Model polymer nanocomposites based on geometrically well defined and protected Laponite particles dispersed in Poly(ethylene oxide) were investigated in order to improve the understanding of the filler dispersion effects on rheology by varying two experimental factors, namely preparation method and PEO matrix molecular weight. Preparation methods are divided into a solution dispersion and a melt dispersion by twin screw extrusion. The linear viscoelastic properties of the samples prepared by solution method revealed an elastic solid like behaviour at Laponite weight fractions as low as 0.1%, dramatically lower than the percolation threshold so far reported for such kind of systems. The sample preparation by melt dispersion, although leading to dispersed particles, does not achieve the same levels of modulus as compared to solution prepared mixtures. We propose a qualitative interpretation of this phenomenon, based on the mixture between a liquid and a dispersed phase of rather solid character. Further experiments using small angle X-ray scattering techniques (SAXS) show that the modulus level is not necessarily related to the height of the correlation peak characteristic of the Laponite stacks. However, for samples prepared with varying PEO matrix molecular weight the fraction of Laponite stacks decreases with increasing PEO molecular weight. The rheology master curve analyses show that confinements of polymer chains arising from high concentrations of particles and high molecular weight matrix chains do not impact the level of the low frequency modulus. However, a slower polymer dynamics, as observed for higher molecular weights, leads to an increase of the modulus at low particle loadings.