bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study of the Thin-Film CdTe Solar Cells with ZnSe/TCO and the CdS/TCO Buffer Layers
Authors: Potlog Tamara , Spalatu Nicolae , Mere Arvo , Hiie Jaan , Mikli Valdek 
Published: September 2011

ABSTRACTThe growth of ZnSe and CdTe thin films by close spaced sublimation is examined. The investigations show that ZnSe films deposited on glass substrates are polycrystalline and exhibit wurtzite-zinc-blende polytypism. The CdTe films grown on glass/SnO2/ZnSe are polycrystalline and have an f.c.c. zinc-blende structure as in the case of a glass/SnO2/CdS buffer layer. The electric and photovoltaic parameters of ZnSe/CdTe solar cells depend on the ZnSe film thickness. Furthermore, it is shown for the first time that the best photovoltaic parameters are achieved using a Zn buffer layer at the interface between ZnSe and CdTe.
Top-Gate Graphene-on-UNCD Transistors with Enhanced Performance
Authors: Yu Jie , Liu Guanxiong , Sumant Anirudha V. , Balandin Alexander A. 
Published: September 2011

ABSTRACTWe 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.
Numerical Study of Scaling Issues in Graphene Nanoribbon Transistors
Authors: Chen Man-Tieh , Wu Yuh-Renn 
Published: September 2011

ABSTRACTThis 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.
Rapid large-scale Characterization of CVD Graphene Layers on Glass using Fluorescence Quenching Microscopy
Authors: Kyle Jennifer Reiber , Guvenc Ali , Wang Wei , Lin Jian , Ghazinejad Maziar , Ozkan Cengiz , Ozkan Mihrimah 
Published: September 2011

ABSTRACTThe exceptional electrical, optical, and mechanical properties of graphene make it a promising material for many industrial applications such as solar cells, semiconductor devices, and thermal heat sinks. However, the greatest obstacle in the use of graphene in industry is high-throughput scaling of its production and characterization. Chemical-vapor deposition growth of graphene has allowed for industrial-scale graphene production. In this work we introduce complimentary high-throughput metrology technique for characterization of chemical-vapor deposition-grown graphene. This metrology technique provides quick identification of thickness and uniformity of entire large-area chemical-vapor deposition-grown graphene sheets on a glass substrate and allows for easy identification of folds and cracks in the graphene samples. This metrology technique utilizes fluorescence quenching microscopy, which is based on resonant energy transfer between a dye molecule and graphene, to increase allow graphene visualization on the glass substrate and increase the contrast between graphene layers.
1/f Noise in Graphene Field-Effect Transistors: Dependence on the Device Channel Area
Authors: Liu Guanxiong , Rumyantsev Sergey , Stillman William , Shur Michael , Balandin Alexander A. 
Published: September 2011

ABSTRACTWe carried out a systematic experimental study of the low-frequency noise characteristics in a large number of single and bilayer graphene transistors. The prime purpose was to determine the dominant noise sources in these devices and the effect of aging on the current-voltage and noise characteristics. The analysis of the noise spectral density dependence on the surface area of the graphene channel indicates that the dominant contributions to the 1/f electronic noise come from the graphene channel region itself. Aging of graphene transistors due to exposure to ambient for over a month resulted in substantially increased noise, which was attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single and bilayer graphene transistors shows a non-monotonic dependence on the gate bias. This observation confirms that the 1/f noise characteristics of graphene transistors are qualitatively different from those of conventional silicon metal-oxide-semiconductor field-effect transistors.
Amine-rich Polyelectrolyte Adhesion Layers as an Alternative to APTES for Surface Immobilization of Biomolecules and Nanostructures
Authors: Stoianov Stefan V. , Ridley Jason I. , Robinson Hans D. 
Published: September 2011

ABSTRACTWe propose the use of amine-rich polyelectrolyte multilayers as a versatile, high quality, tunable adhesive surfaces for biomedical and nanotechnological applications. The films are simple to fabricate under mild conditions and provide at least as good adhesion as standard aminopropyltriethoxysilane terminated glass substrates. In addition, the multilayer surface can be reliably passivated by acetylation with acetic anhydride which reduces the adhesion to the point that non-specific binding of proteins and nanoparticles becomes all but negligible. We demonstrate that this property, in combination with the robustness of the film, makes it possible to pattern the adhesiveness of the film at the nanoscale level.
Large-Area Industrial-Scale Identification and Quality Control of Graphene
Authors: Nolen Craig M. , Denina Giovanni , Teweldebrhan Desalegne , Bhanu Bir , Balandin Alexander A. 
Published: September 2011

ABSTRACTA large-area graphene layer identification technique was developed for research and industrial applications. It is based on the analysis of optical microscopy images using computational image processing algorithms. The initial calibration is performed with the micro-Raman spectroscopy. The method can be applied to the wafer-scale graphene samples. The technique has the potential to be the gateway in the development of fully automated statistical process control methods for the next generation thin-film materials used by the semiconductor industry. The proposed technique can be applied to graphene on arbitrary substrates and used for other atomically thin materials.
All-Carbon Composite for Photovoltaics
Authors: Tan Alvin T.L. , Tung Vincent C. , Kim Jaemyung , Huang Jen-Hsien , Tevis Ian , Chu Chih-Wei , Stupp Samuel I. , Huang Jiaxing 
Published: September 2011

ABSTRACTGraphitic nanomaterials such as graphene, carbon nanotubes (CNT), and C60 fullerenes are promising materials for energy applications because of their extraordinary electrical and optical properties. However, graphitic materials are not readily dispersible in water. Strategies to fabricate all-carbon nanocomposites typically involve covalent linking or surface functionalization, which breaks the conjugated electronic networks or contaminates functional carbon surfaces. Here, we demonstrate a facile surfactant-free strategy to create such all-carbon composites. Fullerenes, unfunctionalized single walled carbon nanotubes, and graphene oxide sheets can be conveniently co-assembled in water, resulting in a stable colloidal dispersion amenable to thin film processing. The thin film composite can be made conductive by mild thermal heating. Photovoltaic devices fabricated using the all-carbon composite as the active layer demonstrated an on-off ratio of nearly 106, an open circuit voltage of 0.59V, and a power conversion efficiency of 0.21%. This photoconductive and photovoltaic response is unprecedented among all-carbon based materials. Therefore, this surfactant-free, aqueous based approach to making all-carbon composites is promising for applications in optoelectronic devices.
Optimizing in vivo Assessment of Nano/bio Interactions to Guide Safer Material Design
Authors: Tanguay Robert. L. , Truong Lisa 
Published: September 2011

ABSTRACTThe rapid rate of discovery and development in the nanotechnology field will undoubtedly increase both human and environmental exposures to engineered nanomaterials. Whether these exposures pose a significant risk remains uncertain. Despite recent collective progress there remain gaps in our understanding of the nanomaterials physiochemical properties that drive or dictate biological responses. The development and implementation of rapid relevant and efficient testing strategies to assess these emerging materials prior to large-scale exposures could help advance this exciting field. I present a powerful approach that utilizes a dynamic in vivo zebrafish embryonic assay to rapidly define the biological responses to nanomaterial exposures. Early developmental life stages are often uniquely sensitive to environmental insults, due in part to the enormous changes in cellular differentiation, proliferation and migration required to form the required cell types, tissues and organs. Molecular signaling underlies all of these processes. Most toxic responses result from disruption of proper molecular signaling, thus, early developmental life stages are perhaps the ideal life stage to determine if nanomaterials perturb normal biological pathways. Through automation and rapid throughput approaches, a systematic and iterative strategy has been deployed to help elucidate the nanomaterials properties that drive biological responses.
The suppression of leakage current in the solid phase crystallized silicon (SPC-Si) TFT employing off-state bias annealing under light illumination.
Authors: Park Sang-Geun , Kuk Seung-Hee , Woo Jong-Seok , Han Min-Koo 
Published: September 2011

ABSTRACTWe fabricated PMOS SPC-Si TFTs which show better current uniformity than ELA poly-Si TFTs and superior stability compare to a-Si:H TFT on a glass substrate employing alternating magnetic field crystallization. However the leakage current of SPC-Si TFT was rather high for circuit element of AMOLED display due to many grain boundaries which could be electron hole generation centers. We applied off-state bias annealing of VGS=5V, VDS=-20V in order to suppress the leakage current of SPC-Si TFT. When the off-state bias annealing was applied on the SPC-Si TFT, the electron carriers were trapped in the gate insulator by high gate-drain voltage (25V). The trapped electron carriers could reduce the gate-drain field, so that the leakage current of SPC-Si TFT was reduced after off-state bias annealing. . We also applied same off state bias annealing at SPC-Si TFT with 20,000 lx light illumination in order to verify the reduction of leakage current of SPC-Si TFT under light illumination. The leakage current of SPC-Si TFT was reduced successfully even under light illumination during off-state bias annealing. The off-state bias annealed SPC-Si TFT could be used as pixel element of high quality AMOLED display.
Utilization of Industrial Inkjet Technologies for the Deposition of Conductive Polymers, Functional Oxides and CNTs
Authors: Voit Wolfgang , Reinhold Ingo , Zapka Werner , Belova Lyubov , Rao K.V. 
Published: September 2011

ABSTRACTPrinting of functional materials requires reliable deposition processes. This work describes the development of printing processes for selected functional materials utilizing industrial-type inkjet printheads. A well-controlled printing process with fluids containing the conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is presented, allowing linear printing speeds of up to 0.35 m/s in single-pass, and smallest line width of approximately 40 μm when printing 7 pL drop volumes. In addition reliable processes for producing ZnO-based films, which enable novel applications for electronic and UV-sensitive devices, and for printing of conductive carbon nanotube layers are shown.
Characteristic band gap structures of high dielectric contrast photonic crystals
Authors: Chao Sheng D. , Peng Hsin Y. 
Published: September 2011

ABSTRACTConventional photonic crystals exhibit low-lying full band gaps for the dielectric contrast smaller than 15. As the dielectric contrast increases, the band gap patterns change characteristics and exhibit interesting properties. In particular, the dispersion curves near the band gap region become concentrated to the middle band frequencies and exhibit an overall red shift in frequency. For a dielectric column photonic crystal made of a hexagonal lattice of circular cylinders, the maximum full band gap was found at the dielectric contrast as high as 27.5, which is attainable by using ceramics materials. The gap opens at high-lying bands, has simultaneous TM and TE band edges, and exhibit flattened dispersion curves near the band edges.
Universal Biomolecule Binding Interlayers Created by Energetic Ion Bombardment
Authors: Bilek Marcela M.M. , McKenzie David R. , Bax Daniel V. , Kondyurin Alexey , Yin Yongbai , Nosworthy Neil. J. , Hirsh Stacey , Fisher Keith , Weiss Anthony S. 
Published: September 2011

ABSTRACTThe ability to strongly attach biomolecules such as enzymes and antibodies to surfaces underpins a host of technologies that are rapidly growing in utility and importance. Such technologies include biosensors for medical and environmental applications and protein or antibody diagnostic arrays for early disease detection. Emerging new applications include continuous flow reactors for enzymatic chemical, textile or biofuels processing and implantable biomaterials that interact with their host via an interfacial layer of active biomolecules. In many of these applications it is desirable to maintain physical properties of an underlying material whilst engineering a surface suitable for attachment of proteins or peptide constructs. Nanoscale polymeric interlayers are attractive for this purpose.We have developed interlayers[1] that form the basis of a new biomolecule binding technology with significant advantages over other currently available methods. The interlayers, created by the ion implantation of polymer like surfaces, achieve covalent immobilization on immersion of the surface in protein solution. The interlayers can be created on any underlying material and ion stitched into its surface. The covalent immobilization of biomolecules from solution is achieved through the action of highly reactive free radicals in the interlayer.In this paper, we present characterisation of the structure and properties of the interlayers and describe a detailed kinetic model for the covalent attachment of protein molecules directly from solution.
A Novel Technology for Green(er) Manufacturing of CNTs via Recycling of Waste Plastics
Authors: Zhuo Chuanwei , Hall Brendan , Levendis Yiannis , Richter Henning 
Published: September 2011

ABSTRACTCostly and often highly-flammable chemicals, such as hydrogen and carbon-containing gases, are largely used for carbon supply in current carbon nanotube (CNT) synthesis technologies. To mitigate related economic and safety concerns, we have developed a versatile CNT synthesis sequence, where low-cost and safe-to-handle-and-store waste solid polymers (plastics) are used for in situ generation of hydrogen and carbon-containing gases. Introduction of different waste plastics, such as polyethylene, polypropylene and polystyrene, into a multi-stage pyrolysis/ combustion/synthesis reactor allows for efficient CNT formation. This process is largely exothermic and scalable. It uses low-cost stainless steel screens to serve both as substrates as well as catalysts for CNT synthesis. This technique enables a solution for both waste plastic utilization and sustainable CNT production.
Siliceous Materials for Immobilization of Photoheterotrophic Bacteria
Authors: Stodolny Mikolaj , Thiel Michal , Wlodarczak Marcin , Laniecki Marek 
Published: September 2011

ABSTRACTPreparation of transparent silica as potential carrier for photocatalysts and photosynthetic bacteria is presented. SiO2 was obtained by sol-gel techniques using tetraethyl orthosilicate as precursor. Glycol and glycerol were used as solvents. The increase of porosity of the studied materials was reached by application of soluble and commercial potato starch as a filler. Calcinations at 825 K for 6 hours removed all organic compounds. The rate of gelation was enhanced applying hydrochloric acid. Different materials were obtained in a series of syntheses with different concentrations of individual components. Transparency of the obtained materials varied between 50 and 97% (in range of λ 350 - 800 nm). Surface area varied between 300 and 400 m2/g and pore diameter was 5 – 18 nm. Samples were studied with SEM, nitrogen sorption at 77 K and UV-Vis spectroscopy. The obtained transparent materials with occluded TiO2 or CaTiO3 were tested in photocatalytic splitting of water.
Carbon Nanotubes Induced Changes in the Phase Diagram and Crystal Structure of 5CB Liquid Crystal
Authors: Georgiev Georgi Y. , McIntyre Michael B. , Gombos Erin A. , Cebe Peggy 
Published: September 2011

ABSTRACTMultiwall Carbon Nanotubes (MWCNTs) form a nematic liquid crystalline (LC) phase in their lyotropic form, enabling their mixing and coupling of their director to that of nematic LCs. An important aspect of this LC/MWCNT interaction, for applications other than display technology, is looking at the ways the MWCNTs affect the physical properties of the LCs. We study the effect of MWCNTs on the nematic to crystal (N-C) phase transition of 4-cyano-4-npentylbiphenyl (5CB). Our Differential Scanning Calorimetry (DSC) results show a dramatic increase in N-C phase transition temperature of 14°C for only 0.1% and of 20°C for 1% MWCNT, due to the crystal nucleation activity of the nanotubes. Using Polarized Microscopy we observe a change in the crystalline order of 5CB from spherulitic at 0% MWCNTs to a multidomain in presence of MWCNTs. The new crystals resemble those formed by a smectic LC 4- Decyloxybenzoic acid. This is in line with predictions from simulations, that the MWCNTs form smectic order in nematic 5CB at their interface. MWCNTs induced modifications of the crystal phase of 5CB promise to create controlled novel crystal forms for the purposes of optical transmission and other applications.
Study on the Mechanical Properties and Creep Behaviour of Carbon Fiber Nano-Composites
Authors: LI Yi-Luen , Chen Wei-Jen , Chiang Chin-Lung , Yip Ming-Chuen 
Published: September 2011

ABSTRACTThe surface modification of carbon nanotubes（CNTs）has been recently observed to influence the distribution of CNTs in epoxy resin and the mechanical properties and electrical conductivities of these CNTs. Accordingly, the treatment of CNTs with organic acids to oxidize them generates functional groups on the surface of CNTs. This investigation studies the consequent enhancement of the mechanical properties and electrical conductivities of CNTs. The influence of adding various proportions of CNTs to the epoxy resin on the mechanical properties and electrical conductivities of the composites thus formed is investigated, and the strength of the material is tested at different temperatures. Moreover, the creep behavior of carbon fiber （CF）/epoxy resin thermosetting composites was tested and analyzed at different temperatures and stresses. The creep exhibits only two stages- primary creep and steady-state creep. The effects of creep stress, creep time, and humidity on the creep of composites that contain various proportion of CNTs were investigated at various temperatures.Creep strain is believed to increase with applied stress, creep time, humidity, and temperature. It also increases as hardness decrease. The test results also indicate that mechanical strength and electrical conductivity increase with the amount of CNTs added to the composites. Different coefficients of expansion of the matrix, fiber and CNTs, are such that overexpansion of the matrix at high temperature results in cracking in it. An SEM image of the fracture surface reveals debonding and the pulling out of longitudinal fibers because of poor interfacial bonding between fiber and matrix, which reduce overall strength.
Influence of Preparation Method and Molecular parameters on the Rheology of Model PEO/ Laponite Nanocomposites
Authors: Jose Jesmy , Omar Abakar Adam , Brotons Guillaume , Tassin Jean-François 
Published: September 2011

ABSTRACTModel 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.
Characterization of Textured PZT Thin Films Prepared by Sol-gel Method onto Stainless Steel Substrates
Authors: Zhao Xuelian , Yu Xufang , Yu Shengwen , Cheng Jinrong 
Published: September 2011

ABSTRACTPbZr0.53Ti0.47O3 (PZT) ferroelectric thin films were deposited on LaNiO3 (LNO) buffered stainless steel (SS) substrates by sol-gel method. The effect of LNO buffer layer on the orientation and electric properties of PZT thin films for different thicknesses were studied. X-ray diffraction (XRD) results indicated that PZT thin films on SS substrates exhibit the (100) preferred orientation with the LNO buffer layers. Scanning electron microscope (SEM) images show that PZT thin films were well crystallized with grain size of about 100 nm. PZT thin films deposited on SS maintain the excellent ferroelectric properties with remnant polarization of about 20 μC/cm2.