bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silicate Formation at the Interface of high-k dielectrics and Si(001) Surfaces
Authors: Schmeisser Dieter , Zheng F. , Himpsel F.J. , Engelmann H.J. 
Published: April 2011

AbstractThe composition and chemical bonding of the first atoms across the interface between Si(001) and the dielectric determine the quality of dielectric gate stacks. An analysis of that hidden interface is a challenge as it requires both, high sensitivity and elemental and chemical state information. We used SR based photoelectron spectroscopies and, in particular, X-ray absorption spectroscopy in total electron yield and total fluorescence yield at the Si2p and the O1s edges to address that issue. We report on results of Hf-oxide prepared by ALD and compare to Pr2O3 / Si(001), and compare the two to the SiO2 / Si(001) system as a reference. For both, Hf-oxide and Pr-oxide thin films we find evidence for the silicate formation at the interface as derived from the characteristic features at the Si2p and the O1s edges.
Interface Engineering During Epitaxial Growth of High-K Lanthanide Oxides on Silicon
Authors: Osten H. Joerg , Czernohorsky Malte , Bugiel Eberhard , Kuehne Dirk , Fissel Andreas 
Published: April 2011

AbstractWe investigated the influence of additional oxygen supply and temperature during the growth of thin Gd2O3 layers on Si(001) with molecular beam epitaxy. Additional oxygen supply during growth improves the dielectric properties significantly; however too high oxygen partial pressures lead to an increase in the lower permittivity interfacial layer thickness. The growth temperature mainly influences the dielectric gate stack properties due to changes of the Gd2O3/Si interface structure. Optimized conditions (600 °C, pO2 = 5·10-7 mbar) were found to achieve equivalent oxide thickness values below 1 nm accompanied by leakage current densities below 1 mA/cm2 at 1 V.
Surface Preparation Techniques for the Atomic Layer Deposition of Hafnium Oxide
Authors: Nyns Laura , Hall Lindsey , Conard Thierry , Delabie Annelies , Deweerd Wim , Heyns Marc , Van Elshocht Sven , Van Hoornick Nausikaa , Vinckier Chris , De Gendt Stefan 
Published: April 2011

AbstractAtomic layer deposition (ALD) has been successfully used over the years for the deposition of conformal dielectric layers with precise thickness down to the nanometer scale. Therefore, optimization of the growth behaviour of the dielectric is mandatory. Since ALD is a surface sensitive growth technique, determined by the amount of available reaction sites at the starting surface, the impact of various wet chemical and thermal Si treatments on the HfO2 growth was evaluated. Thin SiO2 starting layers, based on wet chemical processing, were prepared by using a diluted peroxide mixture and an ozone/DI-water treatment. The thermally grown oxides were gradually etched by slowly immersing the oxidized Si substrate into a diluted HF solution, creating a thickness range on a single wafer. Our results demonstrate that the HfO2 deposition is more dependent on the thickness of the SiO2 layer than on the chemistry used to grow the oxide layer. For all studied oxides, two regions can clearly be distinguished. First, a linear relationship between the oxide thickness and the amount of deposited HfO2 is seen. Because chemical oxides tend to grow in islands, this trend can be explained by an increase in density of surface OH groups when the oxide grows thicker. When an ellipsometric thickness of ~0.8 nm is reached, saturation of the HfO2 growth is obtained. We believe that, from this thickness on, the starting surface is completely covered with hydroxyl groups, leaving the HfO2 growth only dependent on the ALD process itself. Since both the wet chemical as the thermal oxides are showing the same trend in HfO2 deposition, it can be stated that surface preparations can be selected solely based on their ease of processing. However, the electrical results show that there may be a difference between the ozone based wet chemical oxides and the etched thermal oxides, since the latter seems to possess slightly more leakage current. The electrical results will be discussed in more detail during the presentation.
Understanding Structural Changes in Phase Change Memory Alloys
Authors: Fons Paul James , Brewe Dale , Stern Ed , Kolobov A. V. , Tominaga Junji 
Published: April 2011

AbstractIn addition to their wide-spread application in the re-writable optical memory markets, phase-change memory alloys are also poised to take a prominent role in future non-volatile memory applications due to their potential for low-energy usage and indefinite cyclability compared with their silicon-based flash memory counterparts. In contrast with their widespread use, however, the details of the crystalline to amorphous switching process utilized for memory storage remain an active research topic with many details still lacking. Considering the conflicting requirements for high-speed switching, yet long term data storage integrity, a deeper understanding of these materials is essential for insightful application development. We have used x-ray absorption fine structure spectroscopy (XAFS), a technique equally suitable for amorphous and crystalline phases to elaborate details in structural changes in the phase-change process for a variety of phase-change alloys in static measurements. As the kinetics of the switching process are the linchpin for optimizing switching characteristics, we have recently initialted dynamic measurements of light -induced structural changes in Ge-Sb-Te (GST) alloys. These measurements have been carried out synchronously using both femtosecond and nanosecond laser pump pulses in conjunction with 100~ps x-ray pulses generated by an electron storage ring. By synchronously triggering the laser with a variable sub-nanosecond delay, we have been able to use XAFS to probe details of the dynamics of the switching process. Preliminary results learned from this approach applied to GST alloys are presented.
Modeling Considerations for Phase Change Electronic Memory Devices
Authors: Wicker Guy 
Published: April 2011

AbstractThis paper discusses the modeling of phase change, chalcogenide alloy, electrical memory devices. Optical disk modeling, which uses the same alloys has yielded a good understanding of how the material's structural change is related to temperature, time, nucleation of crystallites, and crystal growth. From this base, models of electrical memory behavior have been developed. Modeling the complex electronic nature of the amorphous phase is discussed and suggestions for improving device performance using these models are made.
Localized Light Focusing and Super Resolution Readout via Chalcogenide Thin Film
Authors: Tominaga Junji , Fons Paul , Shima Takayuki , Kurihara Kazuma , Nakano Takashi , Kolobov Alexander , Petit Stephane 
Published: April 2011

AbstractWe have demonstrated that certain chalcogenide layers within a spinning super-RENS optical disc allow to squeeze the 650 nm laser beam to a spot size as fine as 50 nm using a 15-nm chalcogenide film. The near-field light was focused at a depth of just over 30 nm after passing through a chalcogenide film. Finite-difference time-domain (FDTD) simulations also reproduced these results. We suggest that a conductive ring aperture generated in the chalcogenide layers plays an important role in the localized light focusing.
Ag-Sb-S Thin Films Prepared by RF Magnetron Sputtering and Their Properties
Authors: Gutwirth Jan , Wagner Tomas , Vlcek Milan , Drasar Cestmir , Benes Ludvik , Hrdlicka Martin , Frumar Miloslav , Schwarz Jiri , Ticha Helena 
Published: April 2011

AbstractOne of the recent applications of thin chalcogenide films is rewritable optical data recording. This technology is based on reversible phase transition between crystalline and amorphous state and vice versa. Dominant materials for rewritable optical recording are Ge Sb Te and Ag In Sb Te alloys. Material research still continues due to need of increasing storage capacity and data rates. Thin Ag Sb S films were prepared by RF magnetron sputtering as potential candidates for rewritable optical data storage films.There were prepared polycrystalline bulks of AgSbS2. Composition and homogeneity of these bulks were checked by scanning electron microscopy with energy dispersive analysis (SEM EDX) structure and bonding relations were studied by Raman spectroscopy and × ray diffraction (XRD).Targets for RF magnetron sputtering were prepared from pulverized bulks by hot pressing technique. Targets were characterized the same way as bulks.Composition and homogeneity of prepared thin films were characterized by SEM EDX, character (amorphous/crystalline) was studied by XRD. Optical properties (spectral dependence of refractive index) were evaluated on basis of UV Vis NIR spectroscopy and variable angle spectral ellipsometry (VASE).Crystallization abilities were traced by thermal dependence of optical transmission of prepared thin films.
A DoD Perspective on Left Handed Negative Index Materials and Potential Applications
Authors: Browning Valerie , Tanielian Minas H , Ziolkowski Richard W. , Engheta Nader , Smith David R. 
Published: April 2011

AbstractIn the quest for ever smaller, lighter weight, and conformal components and devices for radar and communication applications, researchers in the RF community have increasingly turned to artificially engineered, composite structures (or “metamaterials”) in order to exploit the extraordinary electromagnetic response these materials offer. One particularly promising class of metamaterials that has recently received a great deal of attention are “left-handed” or negative index materials. Because these metamaterials exhibit the unique ability to bend and focus light in ways no other conventional materials can, they hold great potential for enabling a number of innovative lens and antenna structures for a broad range of commercial and DoD relevant applications. Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing Negative Index Materials (NIM) (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties. For this reason the Defense Advanced Research Project Agency (DARPA) has initiated a program that seeks to further develop and demonstrate NIM for future DoD missions including, but not limited to, the following: 1) lightweight, compact lenses with improved optics; 2) sub wavelength/high resolution imaging across the electromagnetic spectrum; 3) novel approaches to beam steering for radar, RF, and/or optical communications; and 4) novel approaches for integrating optics with semiconductor electronics. A brief overview of the salient properties of NIM will be presented as well as a general discussion of a few of their potential applications.
Novel Passive and Active Transmission Line Metamaterial Devices
Authors: Caloz Christophe 
Published: April 2011

AbstractThis paper presents a number of metamaterial (MTM) structures and devices, with emphasis on the so-called transmission line (TL) MTMs, which have lead to most practical applications so far. Both results obtained from 2002 to mid-2005 [1] and recent advances over the past few months are described.
Novel Continuous Poly(vinylidene fluoride) Nanofibers
Authors: Ren Xi , Dzenis Yuris 
Published: April 2011

AbstractPoly(vinylidene fluoride) (PVDF) is well known for its ferroelectric and piezoelectric properties. Currently, this polymer is used in applications in the form of films. PVDF fibers are expected to open up exciting new opportunities such as design and use of active textiles and composites. It is well-known that synthetic fiber properties improve substantially with the decrease of their diameter. However, conventional mechanical fiber spinning processes usually produce fibers with diameters in the range from tens to hundreds of microns. In this work, ultrafine, submicron-diameter continuous PVDF nanofibers were fabricated by electrospinning method. The method consists of spinning polymer solutions in high electric fields. Effects of process parameters on nanofiber diameter and morphology were studied. XRD and FTIR analyses of PVDF nanofibers were performed. The latter indicated that the initial á phase of the raw material was converted to â phase PVDF during electrospinning. As â phase is primarily responsible for the piezo- and ferroelectric properties of PVDF, the latter result is very encouraging. The demonstrated novel continuous PVDF nanofibers can be used in nanostructured active textiles and composites and can lead to unusual new designs for actuators and sensors.
Electrical Percolation in Carbon Nanotube Dispersions: A Mesoscale Modeling and Experimental Study
Authors: Rahatekar Sameer Sharad , Shaffer Milo S P , Elliott James A 
Published: April 2011

AbstractThis paper describes our current work on electrical percolation in carbon nanotubes filled thermoplastic polymer fibers. The objective of this work is to develop an understanding of how the electrical properties of the nanotube/polymer composites are affected by processing conditions, orientation of nanotubes, and their loading fraction. In the first part of the work, mesoscale modelling of nanotubes was carried out using a dissipative particle dynamics method. The percolation threshold required to achieve an electrically conductive network of nanotubes within in a polymer fibre was predicted as a function of orientation and aspect ratio of nanotubes using a Monte Carlo method to measure the network impedance. In the second part of this work, X-ray diffraction analyses were carried out to find the degree of alignment of nanotubes in polyamide 12 fibers.
Eu-Doped Silica Nanotubes: Synthesis and Optical Properties
Authors: Murphy Catherine , Hunyadi Simona E. 
Published: April 2011

AbstractSilver nanowires were coated with a silica shell through an indirect approach. Incorporation of the fluorescent ion Eu(III) into the silica shell in situ was achieved. Subsequent chemical dissolution of the inner metal core resulted in fluorescent silica nanotubes. Transmission electron microscopy (TEM), electron dispersive X-ray microanalysis (EDAX), fluorescence spectroscopy, and zeta potential measurements were used to characterize the materials.
Supramolecular Nanotube Hosts for Encapsulation of 10-nm-Scale Objects
Authors: Shimizu Toshimi 
Published: April 2011

AbstractSupramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self-assembly of cardanol-based glycolipids, glucopyranosylamide lipids, or glucose-based unsymmetrical bolaamphiphiles. Time-resolved fluorescent measurement using 8-anilinonaphtahalene-1-sulfonate (ANS) as a probe revealed that the water confined in a cardanol-based glycolipid nanotube has relatively lower solvent polarity than bulk water, which corresponds to that of 1-propanol. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube, which depends on capillary action, has been examined by filling the lyophilized lipid nanotubes with aqueous dispersions of gold or silver nanocrystals, ferritin, or magnetic crystals. We have also succeeded in filling the unsymmetrical bolaamphiphile nanotube, which possesses positively charged inner surfaces, with negatively charged polymer beads or ferritin without depending on capillary action.
“Scratching” Carbon Nanotubes onto Si Substrates<B>
Authors: Yu Jun , Chen Ying 
Published: April 2011

AbstractLarge-scale, high-density, and patterned carbon nanotubes (CNTs) on both pure Si and quartz (SiO2) substrates have been produced using different approaches. The CNTs were synthesized by pyrolysis of the ball-milled iron phthalocyanine (FePc) in a tube furnace under a Ar-5% H2 gas flow. Because patterned CNTs are difficult to grow directly on smooth and perfect single-crystalline Si wafer surface, mechanical scratches were created to help the selective deposition and growth of CNTs on the scratched areas. This simple process does not require pre-deposition of any metal catalysts. For SiO2 substrates, which can be readily covered by a CNT film, patterned CNTs are produced using a TEM grid as mask to cover the areas where CNTs are not needed. The growth temperature and vapor density have strong influence on the patterned CNT formation. The scratch areas with a special structure and a higher surface energy help the selective nucleation of CNTs.
In-situ Study on Effects of Annealing Temperature and Mo Interlayer on Stress Relaxation Behaviors of Pure Al Films on Glass Substrates
Authors: Park Young-Bae , Hwang Soo-Jung , Lee Yong-Duk , Jung Ja-Young , Joo Young-Chang 
Published: April 2011

ABSTRACTThe in-situ SEM observation of real-time hillock evolution in pure Al thin films on glass substrate during isothermal annealing at 194°C was analyzed quantitatively to understand the compressive stress relaxation mechanism by focusing on the effect of Mo interlayer between Al film and glass substrate. There is a good correlation between the hillock-induced stress relaxation and the measured stress relaxation by wafer curvature method. It is also clearly shown that the existence of Mo interlayer plays an important role in hillock formation probably due to the large difference in interfacial diffusivity of Al films.
Fabrication and Characterization of Flexible, Microfabricated Neural Electrode Arrays Made from Liquid Crystal Polymer and Polynorbornene
Authors: Keesara Varun Vardhan , Durand Dominique M. , Zorman Christian A. 
Published: April 2011

ABSTRACTThis paper reports the development of flexible, neural electrode arrays made from liquid crystal polymer (LCP) and a polynorbornene (PNB) known by its trade name AvatrelTM. Each array consists of a single flexible, polymeric structure composed of an 8 mm-wide pad supporting eight Pt contacts connected to an ASIC mounting pad by a 5 cm-long, 2 mm-wide shaft carrying eight, 50 μm-wide Pt interconnect lines. The Pt conductors sit atop a 50 μm-thick base layer and are isolated from the environment except at the contacts by a capping layer of the same material as the base. In both cases, the devices were fabricated using conventional microfabrication techniques adapted for the particular polymeric material. In the case of LCP, the base structure was fabricated on 50 μm-thick sheets that were laminated and etched into the final structure. In contrast to LCP, PNB is spin castable and photodefinable, which enabled conventional photolithographic patterning techniques to be employed in a straightforward manner. The PNB-based devices could readily be fabricated, however issues related to LCP etching necessitated the development of a multi-step etch process to form the vias that expose the contacts. Electrodes made from both polymers could support electrical loads typical of stimulation applications without failing. A simple cell culture test suggests that Avatrel™ may be biocompatible, at least for short term applications.
Structural and Hydriding/Dehydriding Properties of HoMn2Hx with Cubic and Hexagonal Laves Phase Structure
Authors: Makihara Yoshikazu , Iwata Youichi , Umeda Kazumi , Miyairi Yoshio , Fujii Hironobu 
Published: April 2011

ABSTRACTBoth the cubic C15-type and the hexagonal C14-type Laves phase compounds HoMn2 were successfully prepared. We found that they absorbed hydrogen up to 3.4 atoms per formula unit at room temperature and discharged it at around 490 K, reversibly. Structural and hydriding/dehydriding properties of the host HoMn2 and their hydrides HoMn2Hx have been investigated by powder X-ray diffraction (XRD) and thermogravimetry/differential thermal analysis (TG/DTA). With increasing the hydrogen content, the host C15-type HoMn2 is distorted into a rhombohedral phase at above x = 2.9, while the host C14-type one keeps the hexagonal structure up to x = 3.4. The experimental results obtained from TG/DTA measurement suggest that two possible interstitial sites with different activation energies for hydrogen desorption exist in the C14 HoMn2, while one site in the C15 HoMn2.
H Adsorption On Rh (110) Surface
Authors: Chen Shao-Ping 
Published: April 2011

ABSTRACTWe have used the density functional theory to study the H adsorption phenomena on Rh (110) surface with H coverage from 0.33 to 2.00 mono-layers. We found H atom favors the three-fold coordinated site as observed experimentally. We confirmed the existence of 1x3-H (0.33 H coverage), 1x2-H (0.5 H coverage), 1x3-2H (0.66 H coverage), 1x1-2H (2.0 H coverage) ordered structures. We also found that the proposed 1x3-2H structure for H coverage of 0.66 is not the lowest energy configuration. We have proposed a new 1x3-2H structure which needs to be tested by future experiments. This is a preliminary report and a more detailed description of the work will be published later.
Self-selective Epitaxial Growth of BST Films: toward Nano-composite Structure for Microwave Tunable Devices
Authors: Yamada Tomoaki , Sherman Vladimir O. , Noeth Andreas , Muralt Paul , Tagantsev Alexander K. , Setter Nava 
Published: April 2011

ABSTRACTBa0.3Sr0.7TiO3 (BST) thin film composite structures were fabricated by means of a selective epitaxial growth process. The epitaxial growth of BST on SrRuO3 electrode surface was selectively achieved at 450∼485°C using a prepatterned ultra-thin amorphous BST layer that locally prevented crystallization. This self build-up mechanism resulted in a columnar composite structure, where epitaxial and amorphous BST columns are electrically connected in parallel. The epitaxial BST showed a high permittivity and a high tunability, whereas the amorphous BST showed a significantly lower permittivity and a very weak tunable behavior. The effective permittivity of the composite capacitors decreased linearly upon increasing the amorphous BST concentration q, while the tunability stayed fairly unchanged until q reached 70%, which agrees with the theoretical ferroelectric/dielectric parallel composite model. The results also give indirect evidence of a good separation between both BST phases.
Characterization of Glancing Angle Deposition Thin Film Optical Filters with Engineered Index Profiles
Authors: Gospodyn James , Taschuk Michael T. , Hrudey Peter C. P. , Tsui Ying Y. , Fedosejevs Robert , Brett Michael J. , Sit Jeremy C. 
Published: April 2011

ABSTRACTPeriodic high-/low-index film stacks of Y2O3:Eu were grown with varying periodicities us-ing the glancing angle deposition (GLAD) technique onto silicon and fused silica substrates. Post-deposition annealing at temperatures from 600 to 1000°C for 1 hour in atmosphere was per-formed to enhance the photoluminescent output of the films. The films were optically character-ized using transmission measurements and Mueller matrix ellipsometry. The luminescence was measured using a spectrometer calibrated for absolute intensity measurements using a frequency-quadrupled Nd:YAG pulsed laser as an excitation source. Absolute conversion efficiencies were measured for the films by characterizing the angular emission profile. The angular emission pro-file of the films was found to follow a non-Lambertian emission profile, with peak emission in-tensities at 50° to 60° with respect to the substrate normal.