bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atom Clusters In A 2/1 Cubic Approximant Phase For Understanding The Structures Of Icosahedral Phases
Authors: HIRAGA K. 
Published: April 2011

AbstractTwo types of atom clusters found in the β-(A1PdMnSi) cubic phase, referred to as a 2/1 crystalline approximant, with a composition of approximately Al70Pd23Mn6Si1which is near to the composition Al72Pd20Mn8of the icosahedral phase, are discussed in detail for understanding the structure of the Al-Pd-Mn icosahedral phase. A large dodecahedral atom cluster located at the body-centered position can be divided into 19 atom shells with approximately icosahedral symmetry, and a dodecahedron of the 12th shell internally touches the surface of the cubic unit cell with a lattice constant of 2.0211 nm. At each vertex of the dodecahedron, a small icosahedral atom cluster consisting of 12 Al atoms surrounding a central Pd atom is located. The dodecahedron is connected to each other by edge-sharing, namely by sharing two small icosahedral atom clusters, along the twofold rotational direction, and forms a simple-cubic packing of the atom cluster in the β-(AlPdMnSi) cubic phase. Another atom cluster located at the origin fills up gaps of the simple-cubic packing of the large dodecahedral atom cluster. By using the dodecahedral and bridging atom clusters, the structure of the Al-Pd-Mn icosahedral quasicrystal is discussed.
The Atomic Structure Of The Zn-Mg-Rare-Earth Quasicrystals Studied By High-Resolution Electron Microscopy
Authors: Abe Eiji , Tsai An Pang 
Published: April 2011

AbstractHigh-resolution transmission electron microscopy has been applied to study the real atomic structure of the decagonal (d-) quasicrystal in the Zn-Mg-rare-earth (RE) system, which is the first d-phase based on Frank-Kasper phase. We show that the phase has a novel structure in which the atomic arrangement in the tenfold symmetry plane can simply be interpreted as the Penrose tiling decorated by individual atoms - the simplest realization of the Penrose tiling as a real atomic structure. This is supported by the fact that a similar local atomic configuration exists in the Zn7Mg4crystal structure. This simple structural model is in sharp contras to the idea of atomic clusters, which has been successfully used to describe the structure of quasicrystals in Altransition metal alloys. The present results strongly suggest that the symmetric atomic clusters are not an essential factor for formation of quasicrystals. Instead, a new idea ofquasi-unit-celland itscoveringis applied for structural description. The atomic structure of the Zn-Mg-RE icosahedral phase is also implied to follow the present concept, based on the fact that its related crystalline phases with hexagonal lattices are not built of giant atomic clusters with icosahedral symmetry.
Numerical Simulations Of Plasticity And Fracture In Quasicrystals
Authors: Trebin Hans-Rainer 
Published: April 2011

AbstractDislocation motion and crack propagation are studied in model quasicrystals both by geometrical considerations and large scale molecular dynamics simulations. It turns out that two characteristic features of quasicrystals govern plasticity and the rough appearence of cleavage planes: the phason degree of freedom and the cluster structure.
Electronic Structure Of Quasicrystals
Authors: Belin-Ferré E. 
Published: April 2011

AbstractThe study of the electronic structure of quasicrystals is still a matter of investigations to date. The paper will report several significant experimental results obtained through spectroscopic techniques which involve the bulk material as well as the surface. Comparison is made with data from related crystalline alloys, densities of states calculations and structural models available for icosahedral quasicrystals.
Containerless Solidification Studies Of The 1/1 Phase IN TI-(MN, CRFE)-SI-O Alloys
Authors: Croat T. K , Kelton K. F. , Holland-Moritz D. , Rathz T. J. , Robinson M. B. 
Published: April 2011

AbstractThe nucleation behavior of the 1/1 quasicrystal approximant phase was investigated in Ti-TMSi- O (TM=Mn, Cr, Fe) alloys made near the stoichiometric composition. Containerless solidification studies were performed using electromagnetic (rf) levitation and drop-tube techniques. The solidification microstructures indicate that α-Ti nucleated first in Ti-Cr-Si-O and β-Ti in Ti-Mn-Si-O alloys; the 1/1 phase nucleated and grew on these titanium oxide dendrites. In Ti-Fe-Si-O alloys, the 1/1 phase nucleated and grew directly from the liquid, allowing information on the nucleation rates to be obtained from undercooling data.
Ti/Zr-Based Quasicrystals - Formation, Structure And Hydrogen Storage Properties
Authors: Kelton K. F. 
Published: April 2011

AbstractMost common in Al-3d transition metal(TM) alloys, icosahedral quasicrystals (i-phase) are also found frequently in Ti/Zr-TM alloys. The Ti-TM-Si-O quasicrystals are metastable, produced only by rapid quenching, and are extremely disordered. In contrast, Ti-Zr-Ni i-phases are well ordered and stable, produced by relatively low temperature annealing, nearly 300°C below the melting temperature. Important for both basic and practical reasons, Ti/Zr-based quasicrystals can absorb significant quantities of hydrogen, up to two hydrogen atoms for each metal atom. The formation and structures of these quasicrystals and closely related complex crystal phases are discussed. The hydrogenation properties of these quasicrystals are presented and shown to be competitive with materials in current use for hydrogen storage and battery applications. Results from recent studies using hydrogen as a probe of the local structure of the quasicrystal and crystal approximant are presented.
Determination of Local Fiber Texture in Liquid Crystal Polymer by Electron Diffraction
Authors: Taylor J. , Libera M. , Greeley M. 
Published: April 2011

ABSTRACTThe rigid chain microstructure of thermotropic liquid crystal polymers (TLCPs) permits an ordered morphology to form consequently giving these materials exceptionally high strength. X-ray and neutron scattering techniques effectively determine the semi-crystalline structure of TLCP but lack the spatial resolution needed to detect morphological changes occurring on sub-micron length scales. This research develops an electron optical technique to resolve the local orientation of LCP fibers at resolutions on the order of 100-300 nm. This paper outlines the essential elements of this technique and presents preliminary results showing systematic morphological changes of LCP fiber as a function of position across the fiber diameter.
Microstructure and Morphology of Thermotropic Amphiphilic Liquid Crystalline Materials
Authors: Jung Hee-Tae , Hudson Steven D. , Percec Virgil 
Published: April 2011

ABSTRACTElectron microscopy methods have been used to investigate the structure and morphology of a hexagonal columnar mesophase, formed by novel amphiphilic and dendrimeric liquid crystals. Alignment of the columns is examined by a surface condition that is suitable for the molecular architecture. For all the materials investigated, columns aligned perpendicular to an evaporated carbon surface. In the case of asymmetric amphiphilic compounds, planar alignment of asymmetric compounds was induced by a water surface. However, planar alignment on water was not possible for a symmetric dendrimer. Based on analysis of electron diffraction and images, the dimension and the stiffness of columnar assemblies is found to depend on molecular architecture.
Liquid Crystalline Zinc Chloride
Authors: Martin J. D. , Thornton T.A. 
Published: April 2011

ABSTRACTThe templated syntheses of our zeolite-type frameworks of metal halides frequently result in the formation of glassy phases or viscous liquids that might be described as ambient temperature molten salts. Having discovered that certain of these materials exhibit remarkable birefringence, we have investigated the structure of both the glass and liquid forms of alkylammonium templated zinc chloride materials by neutron and X-ray diffraction, as well as DSC and polarizing microscopy techniques. Further template control using alkylammonium surfactants as directors has yielded an entire family of liquid crystalline materials with up to 90% inorganic content. The compositional dependence of the structure of these liquid crystalline phases suggests that these materials are best described as “solvent-free” lyotropic liquid crystals.
Role of the Cholesteric Phase In The Formation Of Twisted Smectic Structures
Authors: Suh S. W. , Campbell A. L. , Patel J. S. 
Published: April 2011

ABSTRACTThe smectic structure obtained by cooling the material from the cholesteric phase often produces different structures in the twisted ferroelectric configuration, which depends not only on the nature of the material, but also on the rate of cooling. In this paper, we have investigated the origin of this behavior and have concluded that the twist in the cholesteric phase is responsible for the apparent unpredictability. Furthermore, we show that for a given chirality of material and the same rubbing condition at the surface, two possible smectic domains are produced. While the electro-optic properties of both these domains show gray-scale capabilities, these domains have different optical properties. This comparison was made possible by using a specially prepared sample in which we rubbed two glass plates, each with two areas in which the rubbing direction was both horizontal and vertical. Using this sample, we have been able to show that the presence of pitch inversion close to the cholesteric to smectic phase transition is the apparent reason the results can not be reproduced. Furthermore, our experiments clarify the importance of sample cooling rate. If rapidly cooled during the fabrication from the cholesteric to the smectic phase, the sample retains a memory of the non-equilibrium pitch, providing us with a means to capture the desired pitch. This important discovery will aid us in modifying the material as well as carefully tailoring its pitch in order to insure that cooling of the cholesteric material leads naturally to the twisted smectic structure.
Microstructural Development of Dispersion Strengthened Cu Thin Films
Authors: Weiss D. , Kraft O. , Arzt E. 
Published: April 2011

ABSTRACTThe internal oxidation method is applied for the first time to produce a fine dispersion of second phase particles in thin films. A processing route is presented which includes ultra-high vacuum magnetron sputtering of about 1 μm thick alloy films onto Si substrates followed by in situ annealing and oxidation. Two different Cu-base alloys are examined, Cu-Y and Cu-Al, in which the extent of miscibilitiy differs significantly. This has considerable influence on the grain growth behavior. Nanoindention and wafer-curvature experiments show a drastic improvement of both room-temperature and high-temperature strength. Phenomena well known from bulk oxide-dispersion strengthened (ODS) alloys are found to appear in the thin films as well: Results on abnormal grain growth and the formation of creep voids are presented and discussed in terms of particle effects.
Magnetic and Structural Properties of Laser-Ablated Planar and Cylindrical Co Thin Films
Authors: Madurga V. , Vergara J. , Ortega R. J. , de Landazabal I. P. , Favieres C. 
Published: April 2011

ABSTRACTPlanar and cylindrical Co thin films have been obtained by pulsed laser ablation. X-ray diffractograms have shown no crystalline structure for the as-deposited samples, while the 450 °C annealed samples exhibit Co fcc crystalline peaks. The Scanning Tunnelling Microscopy has revealed a small increase of the surface roughness for the annealed films. The Hall effect has been used to determine the value of the spontaneous magnetization, Ms, at room temperature; Ms ≈ 14 kgauss for the as-deposited sample and Ms ≈ 17.6 kgauss for the 450 °C annealed sample. From transverse magnetooptic Kerr effect, it has been found that the as-deposited samples exhibit magnetic bistability, with a coercive field, Hc, °C. Besides, it has been observed an increase of H, up to ≈ 50 Oe, when the annealing temperature increases. The vibrating sample magnetometry has confirmed these results, showing that the magnetization participating in the magnetooptic effect for these low fields is the total spontaneous magnetization of these samples. Moreover, the cylindrical films exhibit magnetoelastic behavior when they are subjected to angular deformation. It has been found that the saturation magnetostriction constant is negative.
Structure and Magnetic Properties of Fe-N Thin Films Grown by ECR Deposition
Authors: émeth Š , Akinaga H. , Boeve H. , Bender H. , de Boeck J. , Borghs G. 
Published: April 2011

ABSTRACTThe growth of FexNy thin films on GaAs, In0.2Ga0.8As, and SiO2/Si substrates using an ultra high-vacuum (UHV) deposition chamber equipped with electron cyclotron resonance (ECR) microwave plasma source is presented. The structural properties of the deposited films have been measured using various techniques as x-ray diffraction (XRD), Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). The results of XRD measurements show that the films consist of a combination of α-Fe, α'-Fe, y-Fe4N, and α”- Fe16N2 phases. The depth profiles, calculated from the Auger peak intensities, show a uniform nitrogen concentration through the films. The TEM reveals a columnar structure of these films. The properties of the different Fe-N layers have been exploited in the fabrication of Fe(N) / FexNy / Fe trilayer structures, where Fe(N) means a slightly nitrogen doped Fe film. The magneto-transport properties of this trilayer structure grown on In0.2Ga0.8As substrates are presented.
Structure, Electrical and Magnetic Properties of Thin Films of La1−xMxMnO3 on Si
Authors: Mateeva N. N. , Hogan P. C. , Dahmen K. H. 
Published: April 2011

ABSTRACTThin films of lanthanum manganates doped with Ca2+, Sr2+, Ba2+ and Pb2+ have been deposited on Si(100) substrate and their electrical and magnetic properties were discussed with respect to the composition, structure and nature of the dopant. Buffer layers of YSZ and La0.8Al0.2O3 were employed and their effect on the materials was studied. Interesting magnetotransport properties were found in some of the films, where there is a large difference between the insulator-metal transition temperature and a ferromagnetic transition temperature.
Film Thickness Monitor for CMP Processing
Authors: Kondo Noriyuki , Hayashi Takahisa , Atsuta Hitoshi , Horie Masahiro , Yoshida Masao , Kimura Norio , Tsujimura Manabu , Yano Hiroyuki , Okumura Katsuya 
Published: April 2011

In the CMP planarization process, detecting the final polishing point is extremely important for maintaining high yield rates. Therefore, various methods for detecting the final polishing point have been developed.We consider it vital that the SiO2 film thickness across a representative area be measured extremely precisely at high speed in the final stages to accurately control film polishing. However, up until now there has not been any wholly satisfactory method to achieve this.In order to measure a fine representative film area (test pattern) both rapidly and accurately, we concluded that the non-contact, non-destructive and highly reliable methods of spectrometric analysis were most promising.Based on these considerations, we developed a compact spectrometric film thickness measurement system which can accurately inspect test patterns at high speeds and installed it adjacent to the CMP equipment's polishing table. Using this system as a film thickness monitor, we can now measure film thickness while rinsing away slurry contaminants, halt polishing at any stage, and calculate the remaining polishing time from the current and desired thicknesses.This system's pattern identification function can automatically measure the film thickness with very fine test patterns (as small as 40 square microns). When used with SiO2 single layer films, the experimental prototype's measurements proved reliably reproducible (showing a deviation of less than 4 nm at 3 σ over repeated trials), and required thirty seconds or less per wafer (including time for pre-alignment and five-point measurement). The system's theoretical basis and actual operations are described below.
Atomically Smooth Ultrathin Oxide Layers on SI(113)
Authors: Müssig H.-J. , Dabrowski J. , Hinrich S. 
Published: April 2011

ABSTRACTWe report the first direct observation of dissociative chemisorption of oxygen molecules on a silicon surface at room temperature via a molecular precursor state. We link this to the fact that smooth oxide layers can be grown easily on Si(113). The process of initial oxidation is discussed in terms of surface diffusion paths and surface stress. First ab initiocalculations help elucidate the favored adsorption sites and the oxidation mechanism. Experimental evidence was found for bond geometries resulting in the quasi-epitaxial growth of a chemisorption layer on the substrate at elevated temperatures (600°C). In contrast to the first stages of Si(001) oxidation, neither defects nor the ejection of Si atoms plays a significant role during the initial oxidation of Si(113).
Bonding Constraints at Interfaces Between Crystalline Si and Stacked Gate Dielectrics
Authors: Lucovsky G. , Phillips J.C. 
Published: April 2011

ABSTRACTThis paper discusses chemical bonding effects at Si-dielectric interfaces that are important in the implementation of alternative gate dielectrics including: i) the character of interfacial bonds, either isovalent with bond and nuclear charge balanced as in Si-SiO2, or heterovalent, with an inherent mismatch between bond and nuclear charge, ii) mechanical bonding constraints related to the average number of bonds/atom, Nay, and iii) band offset energies that are reduced in transition metal oxides due to the d-state origins of the conduction band states. Applications are made to specific classes of dielectric materials including i) nitrides and oxide/nitride stacks and ii) alternative high-K gate materials.
Ultrathin Silicon Dioxide Formation By Ozone On Ultraflat Si Surface
Authors: Kurokawa A. , Maeda T. , Sakamoto K. , Itoh H. , Nakamura K. , Koike K. , Moon D.W. , Ha Y.H. , Ichimura S. , Ando A. 
Published: April 2011

ABSTRACTWe prepared an atomically flat silicon substrate which had a step-terrace structure and observed the topography of the ozone-oxidized surface to clarify whether homogeneous oxidation occurs with ozone. The oxide was formed with high-concentration ozone gas with a thickness of 2.5nm at a temperature of 350°C. The oxide surface still maintained the same step-terrace structure as observed before oxidation, which revealed that ozone-oxidation occurs layer-by-layer and produces an atomically flat oxide. XPS and MEIS analyses show that the stoichiometry of ozone oxide grown at 350°C is the same as that of an oxide grown thermally at 750°C.
Self-Consistent Mosfet Tunneling Simulations—Trends in the Gate and Substrate Currents and the Drain-Current Turnaround Effect with Oxide Scaling
Authors: Massoud H. Z. , Shiely J. P. , Shanware A. 
Published: April 2011

ABSTRACTThis paper discusses the simulation needs of deep-submicron MOSFETs beyond the 100 nm technology generation where the tunneling of carriers through the gate dielectric will become a vital issue in device design, optimization, and characterization. We present simulation results of Tunnel-PISCES, a MOSFET device simulator where tunneling in the gate dielectric is implemented in a self-consistent manner with the device equations in the substrate. Simulation results of trends in the gate, substrate, and drain currents with oxide scaling are presented. The drain-current turnaround effect is explained by considering the role of the voltage drop across the polysilicon gate resistance in determining the device gate tunneling conditions.
Ultrathin Gate Oxide Prepared by Oxidation in D2O for Mos Device Applications
Authors: Kim Hyojune , Hwang Hyunsang 
Published: April 2011

ABSTRACTWe present a novel gate oxidation process using D2O (deuterium oxide) as an oxidizing gas. The electrical and reliability characteristics of ultrathin gate oxide grown in D2O ambient have been investigated. Compared with a control oxide grown in H2O, a oxide grown in D2O exhibits a significant reduction of charge trapping and interface state generation. Based on a secondary ion mass spectroscopy (SIMS) analysis; we found a deuterium rich-layer at the Si/SiO2 interface. The improvement of electrical and reliability characteristics can be explained by the deuterium incorporation at the Si/SiO2 interface.
Spectroscopic Ellipsometry of Ta2O5 ON Si
Authors: Richter C.A. , Nguyen N.V. , Alers G.B. 
Published: April 2011

ABSTRACTIn this paper, we present the results of spectroscopic ellipsometry (SE) studies of Ta2O5 films on Si. Based on these results, we have experimentally determined an effective method for analyzing SE measurements of Ta2O5. A set of CVD-grown Ta2O5 films on silicon – with thicknesses ranging from below 10 nm to approximately 60 nm thick – was investigated by SE in an effort to improve optical film thickness metrology for Ta2O5. The samples were measured across the spectral range 1.5 eV to 6.0 eV by using a well-characterized, high-accuracy rotating-analyzer-type ellipsometer. We present an analysis method, based upon a Tauc-Lorentz parameterization of the optical properties of Ta2O5, that properly describes the SE data. We also demonstrate how optical properties are affected by the presence of an interlayer at the Si/Ta2O5 interface. Our results show small, but meaningful variations in optical parameters resulting from variations in deposition processes and annealing conditions. This work demonstrates that SE can be used successfully to characterize this category of alternate gate dielectrics.
Combined Thermal and UV Growth of Thin Dielectrics on Silicon in an NO Environment
Authors: Jamet Philippe , Tanner Philip , Harrison H. Barry , Dimitrijev Sima 
Published: April 2011

ABSTRACTThe necessity to decrease silicon wafer-processing temperatures substantially has stimulated research into new and innovative techniques for the formation of thin dielectric films. A photo-decomposition technique using Nitric Oxide (NO) is one such promising method. Thermally NO-grown and NO-annealed dielectric films have already shown very encouraging physical and electrical results. This study compares thermally NO-grown oxides with thermally NO grown and assisted by ultraviolet (UV) irradiation. Methods using UV and vacuum UV light generated from low-pressure mercury or deuterium lamps to stimulate the growth of ultrathin dielectric films are described. The oxynitridation of silicon is carried out by irradiating an ultraviolet beam on the heated silicon substrate covered by a thin layer of nitric oxide gas. Typical resultant film thickness were in the range 10 –40 A after oxynitridation for various times at 500°C. MIS devices were fabricated using these films as gate insulators and were electrically characterized. Electrical characterization revealed good film qualities, rendering this new UV-NO oxynitridation technique promising for low temperature (<600°C) semiconductor processing. Films grown in NO ambient under deuterium lamp irradiation followed by NO annealing were also investigated. These results will also be presented.