Showing papers on "Amorphous solid published in 2006"
TL;DR: In this paper, a-IGZO is used as the channel layer for flexible and transparent TFTs. But, the performance of the flexible TFT was evaluated at room temperature and at temperatures up to 500 °C.
Abstract: Recently, we have demonstrated the potential of amorphous oxide semiconductors (AOSs) for developing flexible thin-film transistors (TFTs). A material exploration of AOSs desired as the channel layer in TFTs is most important for developing high-performance devices. Here, we report our concept of material exploration for AOSs in high-performance flexible and transparent TFTs from the viewpoints of chemical bonding and electronic structure in oxide semiconductors. We find that amorphous In–Ga–Zn–O (a-IGZO) exhibits good carrier transport properties such as reasonably high Hall mobilities (>10 cm2V-1s-1) and a good controllability of carrier concentration from <1015 to 1020 cm-3. In addition, a-IGZO films have better chemical stabilities in ambient atmosphere and at temperatures up to 500 °C. The flexible and transparent TFT fabricated using a-IGZO channel layer at room temperature operated with excellent performances, such as normally-off characteristics, on/off current ratios (~106) and field-effect mobilities (~10 cm2V-1s-1), which are higher by an order of magnitude than those of amorphous Si:H and organics TFTs.
1,634 citations
Patent•
18 May 2006TL;DR: In this paper, a light-emitting device with the use of an amorphous oxide was presented, which has a lightemitting layer existing between first and second electrodes and a field effect transistor, of which the active layer is an Amorphous.
Abstract: An object of the present invention is to provide a new light-emitting device with the use of an amorphous oxide. The light-emitting device has a light-emitting layer existing between first and second electrodes and a field effect transistor, of which the active layer is an amorphous.
1,551 citations
TL;DR: In this paper, a-IGZO channels were fabricated using amorphous indium gallium zinc oxide channels by rf-magnetron sputtering at room temperature.
Abstract: Thin-film transistors (TFTs) were fabricated using amorphous indium gallium zinc oxide (a-IGZO) channels by rf-magnetron sputtering at room temperature. The conductivity of the a-IGZO films was controlled from ∼10−3to10−6Scm−1 by varying the mixing ratio of sputtering gases, O2∕(O2+Ar), from ∼3.1% to 3.7%. The top-gate-type TFTs operated in n-type enhancement mode with a field-effect mobility of 12cm2V−1s−1, an on-off current ratio of ∼108, and a subthreshold gate voltage swing of 0.2Vdecade−1. It is demonstrated that a-IGZO is an appropriate semiconductor material to produce high-mobility TFTs at low temperatures applicable to flexible substrates by a production-compatible means.
1,094 citations
TL;DR: In this paper, the structures of various types of amorphous carbon films and common characterization techniques are described, which can be classified as polymer-like, diamond-like or graphite-like based on the main binding framework.
1,004 citations
TL;DR: In this article, a chemical design concept of ionic amorphous oxide semiconductor (IAOS) and its unique electron transport properties, and electronic structure, by comparing them with those of conventional ammorphous semiconductors is addressed.
Abstract: Recently we have reported the room temperature fabrication of transparent and flexible thin film transistors on a polyethylene terephthalate (PET) film substrate using an ionic amorphous oxide semiconductor (IAOS) in an In2O3–ZnO–Ga2O3 system. These transistors exhibit a field effect mobility of ∼10 cm2 (V s)−1, which is higher by an order of magnitude than those of hydrogenated amorphous Si and pentacene transistors. This article describes a chemical design concept of IAOS, and its unique electron transport properties, and electronic structure, by comparing them with those of conventional amorphous semiconductors. High potential of IAOS for flexible electronics is addressed.
820 citations
TL;DR: The construction and performance of dye-sensitized solar cells (DSCs) based on arrays of ZnO nanowires coated with thin shells of amorphous Al(2)O(3) or anatase TiO( 2) by atomic layer deposition is described and it is found that alumina shells of all thicknesses act as insulating barriers that improve cell open-circuit voltage (V(OC) and fill factor with little current falloff.
Abstract: We describe the construction and performance of dye-sensitized solar cells (DSCs) based on arrays of ZnO nanowires coated with thin shells of amorphous Al2O3 or anatase TiO2 by atomic layer deposition. We find that alumina shells of all thicknesses act as insulating barriers that improve cell open-circuit voltage (VOC) only at the expense of a larger decrease in short-circuit current density (JSC). However, titania shells 10−25 nm in thickness cause a dramatic increase in VOC and fill factor with little current falloff, resulting in a substantial improvement in overall conversion efficiency, up to 2.25% under 100 mW cm-2 AM 1.5 simulated sunlight. The superior performance of the ZnO−TiO2 core−shell nanowire cells is a result of a radial surface field within each nanowire that decreases the rate of recombination in these devices. In a related set of experiments, we have found that TiO2 blocking layers deposited underneath the nanowire films yield cells with reduced efficiency, in contrast to the beneficial...
704 citations
TL;DR: The capacitance of the crystallized materials is clearly dependent upon the crystalline structure, especially with the size of the tunnels able to provide limited cations intercalation as discussed by the authors.
Abstract: Manganese dioxide compounds with various structures were synthesized and tested as "bulk" composite electrodes for electrochemical capacitors. The capacitance of the set of MnO 2 compounds having Brunauer-Emmett-Teller (BET) surface areas larger than 125 in 2 g -1 reached a maximum value of about 150 F g -1 . The capacitance of all amorphous compounds (except one) is due to faradaic processes localized at the surface and subsurface regions of the electrode. Further increasing the surface area does not provide additional capacitance. The capacitance of the crystallized materials is clearly dependent upon the crystalline structure, especially with the size of the tunnels able to provide limited cations intercalation. Thus, the 2D structure of birnessite materials gives an advantage to obtain relatively high capacitance values (110 F g -1 ) considering their moderate BET surface area (17 m 2 g -1 ). ID tunnel structure such as γ or β-MnO 2 is characterized by only a pseudofaradic surface capacitance and therefore relies on the BET surface area of the crystalline materials. 3D tunnel structure such as λ-MnO 2 shows some intermediate behavior between bimessite and ID tunnel structures.
623 citations
TL;DR: In this paper, the surface and internal structure of fly ash particles were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to characterize twelve Class F fly ash samples from nine PC power plants in PA, WV, MD and TN.
536 citations
TL;DR: In this paper, a cooperative model based on a strain rate/temperature superposition principle was proposed for compressive yield stress analysis of polycarbonate, polymethylmethacrylate, and polyamideimide.
468 citations
TL;DR: In this article, a wet chemical process for nanoscale texturing of Si surfaces is presented, which results in an almost complete suppression of the reflectivity in a broad spectral range, leading to black Si surfaces.
Abstract: We present a wet chemical process for nanoscale texturing of Si surfaces, which results in an almost complete suppression of the reflectivity in a broad spectral range, leading to black Si surfaces. The process affects only the topmost 200–300nm of the material and is independent of the surface orientation and doping. Thus, it can be applied to various structural forms of bulk silicon (single, poly-, or multicrystalline) as well as to thin Si films (amorphous or microcrystalline). The optical properties of various black Si samples are presented and discussed in correlation with the surface morphology.
458 citations
TL;DR: In this article, the elastic moduli of ultrathin poly(styrene) and poly(methylmethacrylate) (PMMA) films of thickness ranging from 200 nm to 5 nm were investigated using a buckling-based metrology.
Abstract: The elastic moduli of ultrathin poly(styrene) (PS) and poly(methylmethacrylate) (PMMA) films of thickness ranging from 200 nm to 5 nm were investigated using a buckling-based metrology. Below 40 nm, the apparent modulus of the PS and PMMA films decreases dramatically, with an order of magnitude decrease compared to bulk values for the thinnest films measured. We can account for the observed decrease in apparent modulus by applying a composite model based on the film having a surface layer with a reduced modulus and of finite thickness. The observed decrease in the apparent modulus highlights issues in mechanical stability and robustness of sub-40 nm polymer films and features.
TL;DR: In this article, two contrasting approaches, involving either polymer-mediated or fluoride-mediated self-transformation of amorphous solid particles, are described as general routes to the fabrication of hollow inorganic microspheres.
Abstract: Two contrasting approaches, involving either polymer-mediated or fluoride-mediated self-transformation of amorphous solid particles, are described as general routes to the fabrication of hollow inorganic microspheres. Firstly, calcium carbonate and strontium tungstate hollow microspheres are fabricated in high yield using sodium poly(4-styrenesulfonate) as a stabilizing agent for the formation and subsequent transformation of amorphous primary particles. Transformation occurs with retention of the bulk morphology by localized Ostwald ripening, in which preferential dissolution of the particle interior is coupled to the deposition of a porous external shell of loosely packed nanocrystals. Secondly, the fabrication process is extended to relatively stable amorphous microspheres, such as TiO2 and SnO2, by increasing the surface reactivity of the solid precursor particles. For this, fluoride ions, in the form of NH4F and SnF2, are used to produce well-defined hollow spheroids of nanocrystalline TiO2 and SnO2, respectively. Our results suggest that the chemical self-transformation of precursor objects under morphologically invariant conditions could be of general applicability in the preparation of a wide range of nanoparticle-based hollow architectures for technological and biomedical applications.
TL;DR: By controlling the specimen aspect ratio and strain rate, compressive strains as high as 80% were obtained in an otherwise brittle metallic glass, and a systematic strain-induced softening was observed which contrasts sharply with the hardening typically observed in crystalline metals.
Abstract: By controlling the specimen aspect ratio and strain rate, compressive strains as high as 80% were obtained in an otherwise brittle metallic glass. Physical and mechanical properties were measured after deformation, and a systematic strain-induced softening was observed which contrasts sharply with the hardening typically observed in crystalline metals. If the deformed glass is treated as a composite of hard amorphous grains surrounded by soft shear-band boundaries, analogous to nanocrystalline materials that exhibit inverse Hall-Petch behavior, the correct functional form for the dependence of hardness on shear-band spacing is obtained. Deformation-induced softening leads naturally to shear localization and brittle fracture.
TL;DR: It was found that each polymer was able to significantly decrease the nucleation rate of amorphous felodipine even at low concentrations (3-25% w/w), and hydrogen bonding interactions were formed between felodIPine and each of the polymers.
TL;DR: In this paper, an extended structure zone model is proposed for the in-plane alignment of biaxially aligned thin films, which can only be obtained when an overgrowth mechanism drives the microstructural evolution of the thin film.
TL;DR: The impact of oxygen and pressure with related structures on the macroscopic properties of the layers was studied in this paper, which revealed an ultra smooth surface with RMS values of about 1 nm.
Abstract: Indium Tin Oxide (ITO) thin films with a variety of microstructures were deposited using a large area conventional DC magnetron sputtering system for flat panel displays manufacturing. Highly uniform ITO films with an average thickness of ∼100 ± 3 nm on the ∼0.6 m2 substrate area were obtained. Film structures with small amounts of crystalline sites were produced by room temperature deposition, and an entirely amorphous structure with excellent etching properties was achieved through optimized incorporation of hydrogen in the film, providing a significant increase in the crystallization temperature of ITO. Post-annealing of such a sample yielded a randomly orientated polycrystalline structure with superior conductivity and transparency. The polycrystalline ITO films, produced at the sputtering substrate temperature of 200 °C, provided structures with preferential grain orientation in both and directions, controlled by the amount of oxygen and increased process pressure. The impact of oxygen and pressure with related structures on the macroscopic properties of the layers was studied. Morphological features of the films such as phase/grain structure and surface roughness were investigated using SEM and AFM. Layers with an equiaxed grain structure of about 30 nm crystal size revealed an ultra smooth surface with RMS values of about 1 nm. Specific resistivities as low as 150 μΩ cm and transmittance values above 92% at 550 nm wavelength were obtained for polycrystalline layers with preferential grain orientation.
TL;DR: A force field for amorphous silica surfaces based on their macroscopic wetting properties that is compatible with the CHARMM force field and TIP3P water model is developed and used to study the permeation of water through silica nanopores.
Abstract: Amorphous silica is an inorganic material that is central for many nanotechnology appplications, such as nanoelectronics, microfluidics, and nanopore sensors. To use molecular dynamics (MD) simulations to study the behavior of biomolecules interacting with silica, we developed a force field for amorphous silica surfaces based on their macroscopic wetting properties that is compatible with the CHARMM force field and TIP3P water model. The contact angle of a water droplet on a silica surface served as a criterion to tune the intermolecular interactions. The resulting force field was used to study the permeation of water through silica nanopores, illustrating the influence of the surface topography and the intermolecular parameters on permeation kinetics. We find that minute modeling of the amorphous surface is critical for MD studies, since the particular arrangement of surface atoms controls sensitively electrostatic interactions between silica and water.
TL;DR: A novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity is presented.
Abstract: We present a novel quenched solid density functional theory (QSDFT) model of adsorption on heterogeneous surfaces and porous solids, which accounts for the effects of surface roughness and microporosity. Within QSDFT, solid atoms are considered as quenched component(s) of the solid−fluid system with given density distribution(s). Solid−fluid intermolecular interactions are split into hard-sphere repulsive and mean-field attractive parts. The former are treated with the multicomponent fundamental measure density functional. Capabilities of QSDFT are demonstrated by drawing on the example of adsorption on amorphous silica materials. We show that, using established intermolecular potentials and a realistic model for silica surfaces, QSDFT quantitatively describes adsorption/desorption isotherms of Ar and Kr on reference MCM-41, SBA-15, and LiChrosphere materials in a wide range of relative pressures. QSDFT offers a systematic approach to the practical problems of characterization of microporous, mesoporous, ...
TL;DR: Crystalline–crystalline/semiconducting–insulating multicomponent systems offer expanded flexibility for realizing high-performance semiconducting architectures at drastically reduced materials cost with improved mechanical properties and environmental stability, without the need to design all performance requirements into the active semiconductor polymer itself.
Abstract: Blends and other multicomponent systems are used in various polymer applications to meet multiple requirements that cannot be fulfilled by a single material. In polymer optoelectronic devices it is often desirable to combine the semiconducting properties of the conjugated species with the excellent mechanical properties of certain commodity polymers. Here we investigate bicomponent blends comprising semicrystalline regioregular poly(3-hexylthiophene) and selected semicrystalline commodity polymers, and show that, owing to a highly favourable, crystallization-induced phase segregation of the two components, during which the semiconductor is predominantly expelled to the surfaces of cast films, we can obtain vertically stratified structures in a one-step process. Incorporating these as active layers in polymer field-effect transistors, we find that the concentration of the semiconductor can be reduced to values as low as 3 wt% without any degradation in device performance. This is in stark contrast to blends containing an amorphous insulating polymer, for which significant reduction in electrical performance was reported. Crystalline-crystalline/semiconducting-insulating multicomponent systems offer expanded flexibility for realizing high-performance semiconducting architectures at drastically reduced materials cost with improved mechanical properties and environmental stability, without the need to design all performance requirements into the active semiconducting polymer itself.
TL;DR: The thermal conductivity of thin films of the phase-change material Ge2Sb2Te5 is measured in the temperature range of 27°C
Abstract: The thermal conductivity of thin films of the phase-change material Ge2Sb2Te5 is measured in the temperature range of 27°C
TL;DR: Using ab initio calculations, the results show that the metastable structure consists of special repeated units possessing rocksalt symmetry, whereas the so-called vacancy positions are highly ordered and layered and just result from the cubic symmetry.
Abstract: Phase change materials based on chalcogenide alloys play an important role in optical and electrical memory devices. Both applications rely on the reversible phase transition of these alloys between amorphous and metastable cubic states. However, their atomic arrangements are not yet clear, which results in the unknown phase change mechanism of the utilization. Here using ab initio calculations we have determined the atomic arrangements. The results show that the metastable structure consists of special repeated units possessing rocksalt symmetry, whereas the so-called vacancy positions are highly ordered and layered and just result from the cubic symmetry. Finally, the fast and reversible phase change comes from the intrinsic similarity in the structures of the amorphous and metastable states.
TL;DR: In this article, the dilute acid (0.05 M H2SO4) hydrolysis at 175 °C of samples comprised of varying fractions of crystalline (α-form) and amorphous cellulose was studied.
Abstract: The dilute acid (0.05 M H2SO4) hydrolysis at 175 °C of samples comprised of varying fractions of crystalline (α-form) and amorphous cellulose was studied. The amorphous content, based on XRD and CP/MAS NMR, and the product (glucose) yield, based on HPLC, increased by as much as a factor of 3 upon ball milling. These results are interpreted in terms of a model involving mechanical disruption of crystallinity by breaking hydrogen bonds in α-cellulose, opening up the structure, and making more β-1,4 glycosidic bonds readily accessible to the dilute acid. However, in parallel with hydrolysis to form liquid-phase products, there are reactions of amorphous cellulose that form solid degradation products.
TL;DR: Treating X-ray amorphous powder patterns with different solid-state models, ranging from disordered nanocrystalline to glassy and amorphouse, resulted in the assignment of structures in each of the systems examined.
Abstract: The purpose of this paper is to provide a physical description of the amorphous state for pharmaceutical materials and to investigate the pharmaceutical implications. Techniques to elucidate structural differences in pharmaceutical solids exhibiting characteristic X-ray amorphous powder patterns are also presented. The X-ray amorphous powder diffraction patterns of microcrystalline cellulose, indomethacin, and piroxicam were measured with laboratory XRPD instrumentation. Analysis of the data were carried out using a combination of direct methods, such as pair distribution functions (PDF), and indirect material modeling techniques including Rietveld, total scattering, and amorphous packing. The observation of X-ray amorphous powder patterns may indicate the presence of amorphous, glassy or disordered nanocrystalline material in the sample. Rietveld modeling of microcrystalline cellulose (Avicel® PH102) indicates that it is predominantly disordered crystalline cellulose Form Iβ with some amorphous contribution. The average crystallite size of the disordered nanocrystalline cellulose was determined to be 10.9 nm. Total scattering modeling of ground samples of α, γ, and δ crystal forms of indomethacin in combination with analysis of the PDFs provided a quantitative picture of the local structure during various stages of grinding. For all three polymorphs, with increased grinding time, a two-phase system, consisting of amorphous and crystalline material, continually transformed to a completely random close packed (RCP) amorphous structure. The same pattern of transformation was detected for the Form I polymorph of piroxicam. However, grinding of Form II of piroxicam initially produced a disordered phase that maintained the local packing of Form II but over a very short nanometer length scale. The initial disordered phase is consistent with continuous random network (CRN) glass material. This initial disordered phase was maintained to a critical point when a transition to a completely amorphous RCP structure occurred. Treating X-ray amorphous powder patterns with different solid-state models, ranging from disordered nanocrystalline to glassy and amorphous, resulted in the assignment of structures in each of the systems examined. The pharmaceutical implications with respect to the stability of the solid are discussed.
TL;DR: In this article, it was shown that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH) 6 3− or O x Al( OH) 6- x (3+ x )− units.
TL;DR: The role of deformation-induced nanocrystallites on the plasticity of monolithic amorphous alloys was examined using high-resolution transmission electron microscopy in this article.
TL;DR: In this paper, self-organized TiO 2 nanotube-layers were formed by electrochemical anodization of Ti in a HF/H 2 SO 4 electrolyte.
TL;DR: In this article, a morphological study of the bioblends was carried out by means of WAXS and SEM showing immiscible behavior, revealing high degree of interaction of the nanoclays with the aPLA.
Abstract: Biodegradable blends of amorphous poly(lactic acid) (aPLA) and polycaprolactone (PCL) and nanocomposites of these blends were developed by melt blending. A morphological study of the bioblends was carried out by means of WAXS and SEM showing immiscible behavior. The nanocomposites were also characterized morphologically by WAXS, TEM and SEM, revealing high degree of interaction of the nanoclays with the aPLA. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of blending and clay addition on the above-mentioned properties was evaluated.
TL;DR: In this article, the authors investigated the electron control and electron transport mechanisms on amorphous indium zinc oxide (IZO) films and confirmed that H2 introduction into the IZO deposition process was effective to increase carrier density.
TL;DR: In this paper, multi-element nitride films of AlCrTaTiZr high-entropy alloy have been prepared by reactive radio-frequency magnetron sputtering and the influences of nitrogen flow ratio on the chemical composition, microstructure and mechanical properties of the deposited nitride film have been investigated.
Abstract: Multi-element nitride films of AlCrTaTiZr high-entropy alloy have been prepared in this study by reactive radio-frequency magnetron sputtering The influences of nitrogen flow ratio on the chemical composition, microstructure and mechanical properties of the deposited nitride films have been investigated The AlCrTaTiZr alloy film exhibited an amorphous structure, while a simple face-center-cubic solid-solution structure was observed in the nitride films prepared under different nitrogen flow ratios The multi-element AlCrTaTiZr nitride films exhibited much improved mechanical properties as compared with conventional nitride hard coatings of transition metals
TL;DR: In this paper, the authors show that the addition of an element having a positive enthalpy of mixing with the constitutive element in bulk amorphous alloys can increase the plasticity and glass-forming ability, but for a limited composition range.