bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Effects on Charge Transfer Mechanisms of nc-ITO Embedded ZrHfO High-k Nonvolatile Memory Devices
Authors: Yang Chia-Han , Kuo Yue , Lin Chen-Han , Kuo Way 
Published: September 2011

ABSTRACTThe nanocrystalline ITO embedded Zr-doped HfO2 high-k dielectric thin film has been made into MOS capacitors for nonvolatile memory studies. The devices showed large charge storage densities, large memory windows, and long charge retention times. In this paper, authors investigated the temperature effect on the charge transport and reliability of this kind of device in the range of 25°C to 125°C. The memory window increased with the increase of the temperature. The temperature influenced the trap and detrap of not only the deeply-trapped but also the loosely-trapped charges. The device lost its charge retention capability with the increase of the temperature. The Schottky emission relationship fitted the device in the positive gate voltage region. However, the Frenkel-Poole mechanism was suitable in the negative gate voltage region.
RBS, XRD, Raman and AFM Studies of Microwave Synthesized Ge Nanocrystals
Authors: Srinivasa Rao N , Pathak A P , Devaraju G , Saikiran V , Nageswara Rao S V S 
Published: September 2011

ABSTRACTGe nanocrystals embedded in silica matrix have been synthesized on Si substrate by co-sputtering of SiO2 and Ge using RF magnetron sputtering technique. The as-deposited films were subjected to microwave annealing at 800 and 9000C. Rutherford backscattering spectrometry (RBS) has been used to measure the Ge composition and film thickness. The structural characterization was performed by using X-ray diffraction (XRD) and Raman spectrometry. XRD measurements confirmed the formation of Ge nanocrystals. Raman scattering spectra showed a peak of Ge-Ge vibrational mode around 299 cm−1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Surface morphology of the samples was studied by atomic force microscopy (AFM). Variation of nanocrystal size with annealing temperature has been discussed. Advantages of microwave annealing are explained in detail.
Length scales of interactions in magnetic, dielectric, and mechanical nanocomposites
Authors: Skomski R. , Balamurugan B. , Schubert E. , Enders A. , Sellmyer D. J. 
Published: September 2011

ABSTRACTIt is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales. Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences arise because figures of merits are generally nonlinear energy integrals. Furthermore, different physical interactions yield different length scales. For example, the interaction in magnetic hard-soft composites reflects the competition between relativistic anisotropy and nonrelativistic exchange interactions, but such hierarchies of interactions are more difficult to establish in mechanical polymer composites and dielectrics.
Investigation of Amorphous IGZO TFT Employing Ti/Cu Source/Drain and SiNx Passivation
Authors: Lee Young Wook , Choi Sung-Hwan , Lee Jeong-Soo , Kwon Jang-Yeon , Han Min-Koo 
Published: September 2011

ABSTRACTWe successfully fabricated a-IGZO TFTs employing a Ti/Cu source/drain (S/D) and SiNx passivation in order to reduce the line-resistance, as compared to most oxide TFTs that use Mo (or TCO) and SiO2 for their S/D and passivation, respectively. Although passivated with SiNx, the TFT exhibits good transfer characteristics without a negative shift. However, the TFT employing a Mo S/D exhibited conductor-like characteristics when passivated with SiNx. Our investigation suggests that the IGZO oxygen vacancies found in the Ti/Cu S/D are controlled, resulting in low concentrations, and so prevent the SiNx-passivated TFT from having a negative shift.
Theoretical Studies of Structure and Doping of Hydrogenated Amorphous Silicon
Authors: Cai Bin , Drabold D. A. 
Published: September 2011

ABSTRACTIn a-Si:H, large concentrations of B or P (of order 1%) are required to dope the material, suggesting that doping mechanisms are very different than for the crystal for which much smaller concentrations are required. In this paper, we report simulations on B and P introduced into realistic models of a-Si:H and a-Si, with concentrations ranging from 1.6% to 12.5% of B or P in the amorphous host. The results indicate that tetrahedral B and P are effective doping configurations in a-Si, but high impurity concentrations introduce many defect states. For a-Si:H, we report that both B(3,1) and P(3,1) (B or P atom bonded with three Si atoms and one H atom) are effective doping configurations. We investigate H passivation in both cases. For both B and P, there exists a “hydrogen poison range” of order 6 Å for which H in a bond-center site can suppress doping. For B doping, nearby H prefers to stay at the bond-center of Si-Si, leaves B four-fold and neutralizes the doping configuration; for P doping, nearby H spoils the doping by inducing a reconstruction rendering initially tetrahedral P three-fold.
Hierarchical Macroporous Mesoporous Materials for Biodiesel Synthesis.
Authors: Wilson Karen , Lee Adam F , Dacquin Jean-Philippe 
Published: September 2011

ABSTRACTThe combination of dwindling oil reserves and growing concerns over carbon dioxide emissions and associated climate change is driving the urgent development of routes to utilize renewable feedstocks as sustainable sources of fuels. Catalysis has a rich history of facilitating energy efficient selective molecular transformations and contributes to 90% of chemical manufacturing processes and to more than 20% of all industrial products. In a post-petroleum era catalysis will be central to overcoming the engineering and scientific barriers to economically feasible routes to bio-fuels. This article will highlight some of the recent developments in the development of solid acid and base catalysts for the transesterification of oils to biodiesel. Particular attention will be paid to the challenges faced when developing new catalysts and importance of considering the design of pore architectures to improve in-pore diffusion of bulky substrates.
X-ray Diffraction Investigations of TiO2 Thin Films and Their Thermal Stability
Authors: Kužel Radomír , Nichtová Lea , Matěj Zdeněk , Hubička Zdeněk , Buršík Josef 
Published: September 2011

ABSTRACTIn-situ laboratory measurements in X-ray diffraction (XRD) high-temperature chamber and detailed XRD measurements at room temperature were used for the study of the thickness, temperature and time dependences of crystallization of amorphous TiO2 thin films. The films deposited by magnetron sputtering, plasma jet sputtering and sol-gel method were analyzed. Tensile stresses were detected in the first two cases. They are generated during the crystallization and inhibit further crystallization that also depends on the film thickness. XRD indicated quite rapid growth of larger crystallites unlike the sol-gel films when the crystallites grow mainly by increasing of annealing temperature.
Photocarrier Excitation and Transport in Hyperdoped Planar Silicon Devices
Authors: Persans Peter D. , Berry Nathaniel E. , Recht Daniel , Hutchinson David , Said Aurore J. , Warrender Jeffrey M. , Peterson Hannah , DiFranzo Anthony , McGahan Christina , Clark Jessica , Cunningham Will , Aziz Michael J. 
Published: September 2011

ABSTRACTWe report an experimental study of photocarrier lifetime, transport, and excitation spectra in silicon-on-insulator doped with sulfur far above thermodynamic saturation. The spectral dependence of photocurrent in coplanar structures is consistent with photocarrier generation throughout the hyperdoped and undoped sub-layers, limited by collection of holes transported along the undoped layer. Holes photoexcited in the hyperdoped layer are able to diffuse to the undoped layer, implying (μτ)h ∼ 5 × 10−9 cm2/V. Although high absorptance of hyperdoped silicon is observed from 1200 to 2000 nm in transmission experiments, the number of collected electrons per absorbed photon is 10−4 of the above-bandgap response of the device, consistent with (μτ)e < 1 × 10−7cm2/V.
Non-Invasive Characterization for Long-Term Preservation of Cultural Heritage
Authors: France F. G 
Published: September 2011

ABSTRACTDevelopments in non-invasive analytical techniques advance the preservation of cultural heritage materials by identifying and analyzing substrates and media. Spectral imaging systems have been used as a tool for non-invasive characterization of cultural heritage, allowing the collection of chemical identification information about materials without sampling. The Library of Congress has been developing the application of hyperspectral imaging to the preservation and analysis of cultural heritage materials as a powerful, non-contact technique to allow non-invasive characterization of materials, by identifying and characterizing colorants, inks and substrates through their unique spectral response, monitoring deterioration or changes due to exhibit and other environmental conditions, and capturing lost and deteriorated information. The resulting image cube creates a new “digital cultural object” that is related to, but recognized as a distinct entity from the original. The range of data thisobjectcontains encourages multidisciplinary collaboration for the integration of preservation, societal and cultural information.
Growth of Large Grain Polycrystalline Silicon Thin Film on Soda-lime Glass at Low Temperature for Solar Cell Applications
Authors: Wang K. , Wong K. H. 
Published: September 2011

ABSTRACTHigh quality polycrystalline silicon (poly-Si) thin film solar cell was successfully fabricated on soda-lime glass substrates by electron beam (Ebeam) evaporation at low processing temperature. The initial poly-Si seed layer (p+-type 0.5 μm thick) was grown via the aluminum induced crystallization (AIC) method at 450 °C. Prominent interdiffusion and Si crystallization have been observed. X-ray diffraction (XRD) shows that (111) is the dominating crystalline orientation. Post annealing at 450 °C for six hours has produced densely packed Si grains with dimension of more than 10 μm in the plane of the film. Non-destructive Raman spectroscopy reveals the remarkable crystalline improvement for samples after thermal treatment. After removing the top diffused Al by chemical means, an absorber layer (p-type) of 0.9 μm thick was subsequently deposited onto the seed layer by Ebeam evaporation at 500 °C. Transmission electron microscopy (TEM) confirmed good homo-epitaxial growth. Without breaking the high vacuum, an n-type amorphous Si (a-Si) layer (0.7 μm thick) was coated onto the absorber layer to form p-n junction. The corresponding I-V characteristics suggest that our low temperature processing technique is applicable for production of poly-Si thin film solar cell on low cost substrates.
Low Temperature Biomass Deconstruction by Zeolite-encapsulated Enzyme Mimics
Authors: Davis L. Shannon , Eisenhart Thomas T. , Hughes Brianna C. , Pressley Amy L. 
Published: September 2011

ABSTRACTOxidation catalysis is a reaction necessary for the production of plastics and other materials that seem now essential to our everyday lives. Unfortunately, most oxidation processes suffer from poor selectivity or yields, creating unwanted byproducts and waste. In nature, oxidative enzymes like methane monooxygenase and the family of cytochromes provide a more selective method for oxidation of organic compounds. Of particular interest is the low temperature, selective oxidation of cellulosic biomass for the production of biofuels or other useful replacements for materials currently derived from petroleum feedstocks. An enzymatic approach could replace the high temperature pyrolysis technology in use today. A series of inorganic mimics of some oxidative enzymes, using transition metal – amino acid complexes encapsulated in large pore zeolites have been synthesized and examined as oxidation catalysts under benign conditions. Several of these demonstrate turnovers comparable to native enzymes in the reaction of model compounds for the oxidation of lignin and cellulose.
Multi-Ion Beam Lithography and Processing Studies
Authors: Appleton Bill R. , Tongay Sefaattin , Lemaitre Maxime , Gila Brent , Hays David , Scheuermann Andrew , Fridmann Joel 
Published: September 2011

ABSTRACTThe University of Florida (UF) have recently collaborated with Raith Inc. to modify Raith’s ion beam lithography, nanofabrication and engineering (ionLiNE) station that utilizes only Ga ions, into a multi-ion beam system (MionLiNE) by adding the capabilities to use liquid metal alloy sources (LMAIS) to access a variety of ions and an EXB filter for mass separation. The MionLiNE modifications discussed below provide a wide range of spatial and temporal precision that can be used to investigate ion solid interactions under extended boundary conditions, as well as for ion lithography and nanofabrication. Here we demonstrate the ion beam lithographic capabilities of the MionLiNE for fabricating patterned arrays of Au and Si nanocrystals, with nanoscale dimensions, in SiO2 substrates, by direct implantation; and show that the same directwrite/maskless-implantation features can be used for in situ fabrication of nanoelectronic devices. Additionally, the spatial and temporal capabilities of the MionLiNE are used to explore the effects of dose rate on the long-standing surface morphological transformation that occurs in ion bombarded Ge.
Raman scattering study of Si nanoclusters formed in Si through a double Au implantation
Authors: Sahu Gayatri , Mahapatra D.P. 
Published: September 2011

ABSTRACTA sequential two step 32 keV Au implantation and 1.5 MeV Au irradiation technique has been used to synthesize Si nanoclusters (NCs) in Si. The low energy amorphising implantation has been carried out over a fluence range of (1 – 100) × 1015 cm−2 while the high energy recrystallizing irradiation fluence was fixed at 1 × 1015 cm−2. Samples were further annealed in air at temperatures between 500° to 950° C for a fixed annealing time of 1 hr and were characterized using Raman scattering at an excitation wavelength of 514.5 nm. Results on as-implanted and irradiated samples indicate formation of strained NCs in the top amorphised layer. Annealing around 500°C has been found to result in strain relief after which the data could be well explained using a phonon confinement model with an extremely narrow size distribution.
Broadband Antireflecting Conductive Metamaterial Films
Authors: Pishbin Nafiseh , Crouse David , Bendoym Igor , Crouse Michael 
Published: September 2011

ABSTRACTA polarization-independent, broadband, antireflecting compound aperture array is designed, fabricated and characterized. The structure is composed of an aluminum film with a periodic array of perforations (apertures) configured in a square lattice with a unit cell consisting of two apertures with different diameters, both filled with silicon oxynitride. Light-channeling waveguide cavity modes of different energies are excited within the two different apertures within each unit cell thereby transmitting different parts of the solar spectrum into the substrate. Experimental characterization shows low reflection (<10%) and low diffuse backscatter. Numerous applications of the films include light detecting and emitting structures and devices.
Development of Electrochemical Copper Deposition Screening Methodologies for Next Generation Additive Selection
Authors: Ryan Kevin , Dunn Kathleen , van Eisden Jobert 
Published: September 2011

ABSTRACTTo reduce time-to-knowledge and costs associated with wafer scale processing a laboratory scale copper electrochemical deposition (ECD) system was developed for screening new organic additives which promote bottom-up fill in interconnect trenches and vias. This new setup enables working process conditions and functionality trends to be identified for open source and proprietary suppressors and levelers at leading edge feature sizes (sub 50nm). The laboratory results can then be compared to the in-line wafer scale plating tool results to ensure their compatibility. A reliable laboratory setup that can mimic the dynamic conditions found inside the wafer scale plating tool will enable the main objective of this work to be efficiently realized. The main objective is to test two previously published models describing copper fill inside the trenches by bridging the gap between fundamental electrochemical measurements and wafer scale plating results. To date this work will focus on the reliability and transferability of plating results between the laboratory setup and a wafer scale plating tool and present preliminary data using gap fill and bottom-up growth ratio as performance metrics.
Imprint resist properties for bit patterned media (BPM)
Authors: Lille J. , Karis T. , Vasquez D. , Wu T-W. 
Published: September 2011

ABSTRACTNanoimprint lithography is a low cost method which produces trillions of nanostructures on a substrate. One application of this technology is patterned magnetic media where a single imprint on a disk can create a masking layer with more than a trillion nanostructures. Several challenges exist to imprinting bit patterned media (BPM) at a density greater than 1Tbit/in2. This technology would allow an extension of hard drive magnetic recording at densities greater than 1Tbit/in2. One such challenge is imprint resist mechanical properties where the imprinted masking layer should be free of thickness variations and resist flop-over. Herein we describe the nanoindentation mechanical properties of several imprint resist systems along with analysis of imprinted features of BPM at densities between 200-482 Gdots/in2.
Rare Earth Materials Challenge to National Defense: Material Scientist’s Perspective
Authors: Hullavarad Shiva , Hullavarad Nilima , Cook Joclyn 
Published: September 2011

AbstractThis article provides the key technical niche that alternative rare earth metals and oxides can offer as an alternative to the ones that are under ‘Potential China Export Embargo’. The potential areas of national interest that affected by limited rare earth and the implications of such short supplies on the US businesses are discussed. The paper discusses the technology areas where US based academic and industries have an opportunity in developing the alternate rare earth materials (REM) through innovations in recycling existing rare earth (RE) metals/oxides and develop alternate solutions. Some examples are provided on how the nanotechnology research in the alternative material technologies in the rare earth metals and oxide materials significantly affect the industry trend of rare earth dependence.
Enhanced adhesion of coating layers by Ion Beam Mixing: An application for nuclear hydrogen production
Authors: Park Jae-Won , Kim Hyung-Jin , Yeo Sunmog , Hong Seong-Duk 
Published: September 2011

ABSTRACTThe bonding between two dissimilar materials has been a problem, partiularly in coating metals with non-metallic protective layer. In this work, it is demonstrated that a strong bonding between ceramics/metal can be achieved by mixing the atoms at the interface by ion-beam. Specifically, SiC coating on Hastelloy X was studied for a high temperature corrosion protection. Auger elemental mapping across the interface shows a far broader mixed region than the region expected by SRIM calculation, which is thought to be due to the thermal spike liquid state diffusion. The results showed that, although the thermal expansion coefficient of Hastelloy X is about three times higher than that of SiC, the film did not peel-off at above 900 oC confirming excellent adhesion. Instead, the SiC film was cracked along the grain boundary of the substrate above 700 oC. At above 900 oC, the film was crystallized forming islands on the substrate so that a considerable part of the substrate surface could be exposed to the corrosive environment. To cover the exposed area, it is suggested that the coating/IBM process should be repeated multiply.
Hollow ZnO Nano-cone Synthesis via Catalyst Free MOCVD
Authors: Zhang Wei , Strobl Karlheinz 
Published: September 2011

ABSTRACTZinc oxide is a wide band gap material with excellent semiconducting, photonic and piezoelectric properties. In the past ten years zinc oxide nano-structures such as nanowires and nanorods have received great interest due to their unique dimensional and material properties in the area of photonics, electronics, mechanics, energy recovery, etc. In this paper we report the manufacturing process of a new shape, i.e. hollow hexagonal ZnO nano-cones. We grew them on different kinds of substrate using a low pressure, catalyst free, metal organic chemical vapor deposition (MOCVD) process on a FirstNano EasyTube 3000™ MOCVD system. Nitrogen was used as carrier gas to bring the reactants, DEZ and H2O, to the substrate surface. At the right balance of process temperature and carrier/precursor gas flow rate the ZnO nano-structure transitioned into a hollow hexagonal cones growth mode. The both one and two dimensional aspects of these catalyst free hollow hexagonal ZnO nano-cones, which are novel to the best of our knowledge, could lead to new applications in photonics, near field probing, chemical sensors, quantum confinement, electronic, etc.
Thin Film Power Harvesting System for Displays
Authors: Ahnood Arman , Chaji Reza , Nathan Arokia 
Published: September 2011

ABSTRACTAn amorphous silicon (a-Si:H) thin film transistor (TFT) circuit designed for charging of an energy storage device using a photovoltaic (PV) array is presented. The TFT circuit is fabricated at plastic compatible temperatures (∼150°C) and as such can easily be integrated within a range of platforms including flexible displays. The circuit provides a high degree of output voltage stability over a range of light intensities and device stress.
Investigations on the Aging Effect of Supercapacitors
Authors: Parigi F. , Gao Y. , Casares M. , Gachovska T. , Zhou Y. S. , Lu Y. F. , Patterson D. , Hudgins J. L. 
Published: September 2011

ABSTRACTIn this paper, the degradation processes of commercial supercapacitors aged at 2.7 V and 65 °C for 2000 h were studied. The crystallinity, thermal stability, and specific surface areas of the carbon electrodes of the supercapacitors were measured. Significant changes and degradations in the carbon electrodes were observed for the aged supercapacitors. New functional groups were also found on the surface of the electrodes. The degradation of the lattice structures and the reduction in the specific surface area were as well observed for the aged supercapacitors. It was suggested that the aging of supercapacitors significantly changed the electrode surface which affects considerably electrical properties and functionality of supercapacitors. We have also performed experiments which suggest that the aging effect on the electrode is not uniformly distributed through its length.