bluuebunny/crossref_metadata_2025_split huggingface dataset:
YMnO3 and YbMnO3 Thin Films for fet type FeRam Application
Authors: Fujimura Norifumi , Yoshimura Takeshi , Ito Daisuke , Ito Taichiro 
Published: April 2011

AbstractWe have been proposing the use of RMnO3 (R: rare earth elements) films for metalferroelectric- semiconductor field effect transistor (MFSFET)-type ferroelectric random access memories (Ferroelectric RAMs). This report describes the progress of YMnO3 and YbMnO3 films for FET type FeRAM application. Although highly (0001)-oriented YMnO3 films are easily obtained on a MgO, ZnO/Sapphire, Pt/Sapphire and Pt/Si substrates, it was very hard to obtain the crystalline films directly on Si or on SiO2/Si substrate. A Y-Mn-O buffer layer improved the crystallinity of the YMnO3 films on Si, and we got the C-V curve with ferroelectric hysteresis. The real ferroelectric component responsible for the C-V hysteresis was calculated to be just 8.4 nC/cm2 by pulse measurements. On the other hand, Y2O3 buffer layer drastically improved the dielectric properties. The window width of the C-V hysteresis does not change by changing the sweep rate and measurement frequency.
Improvement of Hydrogen Degradation in Pt/SrBi2Ta2-xNbxO9/Pt Capacitor
Authors: Furuya Akira , Cuchiaro Joe D. 
Published: April 2011

AbstractFerroelectric SrBi2(Ta1-xNbx)2O9 (SBTN) thin films are under evaluation for IC memory applications. It has been reported that SrBi2(Ta1-xNbx)2O9 has higher fatigue endurance and imprint resistance than other common ferroelectric materials such as lead zirconate titanate (PZT). One of the most important technical issues for integrating ferroelectric oxide materials into IC memory applications is the degradation of ferroelectric capacitor properties from the oxide reduction from hydrogen. Hydrogen annealing processes performed to terminate dangling bonds in silicon, or, elevated temperature processes, which dissociate hydrogen, are expected to reduce the ferroelectric oxide thereby degrading the dielectric properties. Therefore, in this work, we have investigated reducing degradation of Pt/SBTN/Pt capacitors due to hydrogen exposure by evaluating the compositional dependence of the Ta/Nb ratio and incorporating TiN as a hydrogen diffusion barrier. To investigate compositional dependence, the Pt/SBTN/Pt capacitors with the desired composition were fabricated from enhanced metal organic decomposition solutions that were spin deposited and delineated with a conventional patterning and etching techniques. Post annealing the samples in H2 (1%)-N2 ambient at 200°C for 10–60min, hysteresis and current-voltage measurements were conducted to evaluate any degradation to pre-anneal measurements. This experimental condition revealed that the best electrical characteristics were obtained with the Ta/Nb ratio of 1.5/0.5. Therefore, Pt/SBTN/Pt capacitors with a Ta/Nb ratio of 1.5/0.5 were evaluated using a TiN barrier and its effect characterized. After depositing a TiN film on the Pt/SBTN/Pt capacitors, the samples were annealed in H2 (5%)-N2 at 400°C for 10–60 min. The TiN was removed with NH4OH: H2O2: H2O = 1: 3: 1, respectively, at 60 - 70°C and the hysteresis and current-voltage characteristics of the capacitors measured. It was found that the degradation was extremely reduced by incorporating a TiN barrier. Moreover, the degradation effects decreased with increased density of the deposited TiN film. TiN densities greater than 3.8g/cm3 in these experiments kept the leakage current degradation to less than 10−6A/cm2 while the degradation in remanent polarization is less than 20%.
The Influence of 5- and 6-Atom Rings on the Optical Properties of Amorphous Silicon Nitride. A Cluster Simulation
Authors: Valladarest R.M. , Calles A.G. , Valladares Alexander , Valladares Ariel A. 
Published: April 2011

ABSTRACTWe simulate α - Si21 –N2: H that contains 6-atom boat-type rings and a – Si17–iNi: H that contains 5-atom planar rings, where i = 0, 1 or 4. The simulations were carried out using the DFT-LDA approximation contained in the DMol code of MSI. We report calculations of impurity levels and relate these to the size of the gap and to the optical absorption curves for each cluster. A comparison is made between the two α – SiN clusters studied to analyze the effect of the ring topology.
Local Basis Gw Calculations and the Dielectric Response of Si and C Clusters
Authors: Yu Ming , Ulloa Sergio E. , Yang Sang H. 
Published: April 2011

ABSTRACTWe describe our progress in developing an ab initio computational scheme for the calculation of the dielectric response function of solids, with special emphasis here on Si and C clusters. All calculations are carried out employing a basis of localized atomic-like orbitals and include the evaluation of quasiparticle corrections. The self-energy operator is evaluated in the GW approximation, with a full frequency dependence for the dielectric matrix. The approach is convenient and computationally optimal for the calculation of optical properties of complex systems lacking full periodicity, such as surfaces and clusters. We present here the dielectric response functions of clusters with structures found after full equilibration via molecular dynamical simulations, and discuss the sensitivity of the optical properties to quasiparticle corrections.
Effect of Preparation and Impurities on The Size and Shape of The Crystallites and on The Crystal Symmetry of Superionic PbSnF4
Authors: Dénès Georges , Cecilia Madamba M. 
Published: April 2011

AbstractThe highest performance fluoride ion conductor, PbSnF4, has been applied for the fabrication of an ambient temperature amperometric oxygen sensor, where it is used in the polycrystalline form. However, the structure of this material is highly anisotropic, thus one could expect polycrystalline samples to give a performance strongly dependent on crystallite direction. We have shown that the tin electronic structure has a very strong influence on the local structure, which determines the preferred direction of crystal growth, which is itself responsible for the crystal shape. This, in turn, determines the direction of preferred orientation, which can dramatically alter the properties relative to a randomly oriented sample. The effect of minor impurities on the size of the crystallites and on the crystalline symmetry has been studied.
Influence of The Electrochemical Environment on Diffusion Processes Near Step and Island Edges: Ag(111) and Ag(100)
Authors: Haftel Michael I. , Einstein T. L. 
Published: April 2011

AbstractThe electrochemical cell provides a potentially powerful means of altering morphology and islanding phenomena on metallic surfaces. Diffusion and attachment processes on terraces and near step and island edges are known to profoundly affect island sizes, shapes and coarsening kinetics. Using the surface-embedded-atom-model (SEAM) for describing metallic surfaces in the electrolytic environment, we calculate the dependence of the activation energies for the aforementioned diffusion processes on the deposited surface charge for the Ag(111) and Ag(100) surfaces in an electrolytic environment. While all these processes show some degree of dependence on the potential, the step-edge barrier and the edge diffusion processes are the most sensitive. Step-edge barriers increase (to over 1 eV) with large positive potential (0.85 V), while edge diffusion barriers monotonically decrease with positive surface charge on Ag(100) and Ag(111). We assess the effect these diffusion barriers have on island size/shapes and coarsening dynamics and discuss the implications on electrochemical tuning of islanding phenomena.
Interrogation of Alumina Grain Boundaries using Atomic Force Microscopy
Authors: Tibble P.A. , Heywood B.R. , Richardson R. , Barnes P. 
Published: April 2011

AbstractA number of MgO doped (3wt%) polycrystalline alumina samples were prepared. The preparation of these samples varied; different regimes for annealing (1500 – 1600°C) and a range of dwell times were examined. Atomic force microscopy (AFM) was used to study surface features. Information on grain boundary dimensions (depth, width) is presented along with a study of grain particle size. The growth of the grain boundaries was found to contradict Mullins' theory of uniform growth with time. We also present evidence for Ostwalds' ripening and the preferential growth of [001] oriented grains.
Modelling Solid Nucleation and Growth In Supercooled Liquid
Authors: Leonard J.P. , Im James S. 
Published: April 2011

AbstractIn this paper, we present a numerical model that incorporates algorithms to simulate nucleation and growth in supercooled liquid in a manner that properly accounts for the stochastic nature of nucleation. The basis of our model relies on a discretization of space and time to address thermal evolution, rapid growth of the undercooled interface, and nucleation in supercooled liquid. The present formulation of nucleation permits the spatially and temporally random nature of the phenomenon to be manifested in the transformation and resultant microstructure. This is accomplished by (1) calculating the probability of nucleation in each and every liquid node during each time step using the Poisson expression, and (2) triggering nucleation if and only when the random number assigned to a node for the time step is less than the calculated nucleation probability. No empirical or deterministic conditions for nucleation are imposed; nucleation occurs spontaneously and solely based on nucleation kinetics. We demonstrate the effectiveness of the overall model by analyzing conditions similar to those encountered in pulsed laser-induced crystallization of thin Si films, and discuss the generality of the proposed stochastic formulation of nucleation.
Morphology Control of Sulfide in Fe-Cr-S alloys during the solidification
Authors: Oikawa Katsunari , Ikeshoji Tamio , Mitsui Hajime , Ishida Kiyohito 
Published: April 2011

AbstractThe evolution of sulfide morphology in the Fe- (0.3 to 18) mass% Cr -0.3 mass% S alloys during solidification and its modification by additions of elements such as Mn, Ti, Zr and C have been investigated by means of optical microscopy, scanning electron microscopy and X-ray diffraction. The sulfide morphologies in the Fe-Cr-S ternary alloy are classified under three types: (i) cellwall (ii) fine particle and (iii) globular sulfides. The iron-rich cellwall sulfide is formed in the Fe-(0.3-1) %Cr-0.3 %S alloys. This sulfide morphology changes to the globular type with increasing Cr content and the size of that is more than 51gm. Fine sulfide particles of size smaller than 2 gtm also coexist in the Fe-(0.3-5) %Cr-0.3 %S alloys. Zr or Ti additions change this morphology from the globular type to the rod-like type in the Fe-18 %Cr-0.3 %S alloy, but Mn addition does not have the same effect. The mechanism of the formation of different sulfide morphologies is discussed on the basis of phase diagram information.
A Molecular Dynamics Study of Implant-Induced Erosion of A (100)-Silicon Stepped Surface
Authors: Mazzone A. M. 
Published: April 2011

AbstractThe purpose of these simulations is to study the mechanisms leading to surface damage during low-energy implants. Therefore the bombarded surface has a realistic vicinal structure and contains one step edge, SA or SB. The damaging event is produced by an atom, Ar or Si, of a low kinetic energy (≤ 30eV), moving on the surface or below it. The simulation indicates a total etching of the first two layers of silicon and the ejection of the implanted Ar. These features are independent on the step structure, on the direction of motion of the moving atom and they hold over a broad range of temperatures. However. if Ar and Si move below this critical depth, they may remain in the lattice as interstitials. The preferred location of these defects is the tetrahedral location at the center of the hexagonal rings. In addition to the formation of interstitials, also a corrugation of the atomic rows on the surface is observed. This effect has a characteristic dependence on the step structure and it is remarkably more pronounced for the SB non-rebonded steps than in the other cases.
Molecular Dynamics Simulations of Growth and Low-Energy Ion Polishing of Thin Molybdenum Films for EUV Multilayer Mirrors
Authors: Klaver Peter , Goedheer Wim , Bijkerk Fred , Thijsse Barend J. 
Published: April 2011

AbstractWe report on the simulation of the growth and subsequent krypton ion polishing of thin molybdenum films, required for extreme ultraviolet multilayer mirror fabrication. We have used a comprehensive Molecular Dynamics (MD) code, principally enabling a simulation of the deposition, ion bombardment and annealing processes. Ion energies used are in the sub-keV range, and the ion angle of incidence is varied between 30 and 60 degrees off-normal.The effects of ion polishing on the surface roughness are discussed, as well as the increase in (surface) atom mobility. We also report data on sputtering yields, ion penetration depths, trapping, energy transfer and krypton implantation and saturation.The results are compared with TRIM results, and the relevance of MD and TRIM simulations for specific purposes is discussed. Also, the effects of short-time, high-temperature annealing of an amorphous film are investigated.
Growth of Co ON Ag(100): A Comparison of Ultra Low Energyion Beam Deposition and Thermal Deposition
Authors: Degroote B. , Dekoster J. , Degroote S. , Pattyn H. , Vantomme A. , Langouche G. , Hou M. 
Published: April 2011

AbstractWe have investigated the growth of Co deposited on Ag(100) with ultra low energy ion beam deposition. The preferred sites of nucleation, the island densities and heights are determined with scanning tunneling microscopy. Submonolayers of Co were ion beam deposited at 300 K using energies between 5 and 30 eV. Preferential growth of islands on the upper side of the mono-atomic Ag steps (i.e. step decoration) is observed for deposition energies of 5 and 15 eV. In addition, 3–4 ML deep holes are formed in the Ag substrate for deposition at 5 eV. At higher deposition energies, the number of holes per surface area decreases. The results are compared with experiments on thermal deposition of Co on Ag(100) as a function of substrate temperature, performed in a previous study.
Electron Holography of Nanostructured Magnetic Materials
Authors: Dunin-Borkowski R. E. , Kardynal B. , Mccartney M. R. , Scheinfein M. R. , Smith David J. 
Published: April 2011

AbstractOff-axis electron holography and micromagnetic calculations that involve solutions to the Landau-Lifshitz-Gilbert equations are used to study magnetization reversal processes in lithographically patterned submicron-sized Co and Co/Au/Ni magnetic elements.
In-Situ Annealing Transmission Electron Microscopy Study of Pd/Ge/Pd/GaAs Interfacial Reactions
Authors: Radulescu F. , Mccarthy J.M. , Stach E. A. 
Published: April 2011

AbstractIn-situ TEM annealing experiments on the Pd (20 nm) / a-Ge (150 nm) / Pd (50 nm) GaAs ohmic contact system have permitted real time determination of the evolution of contact microstructure. As-deposited cross-sectional samples of equal thickness were prepared using a focused ion beam (FIB) method and then subjected to in-situ annealing at temperatures between 130-400 °C. Excluding Pd-GaAs interactions, four sequential solid state reactions were observed during annealing of the Pd:Ge thin films. First, interdiffusion of the Pd and Ge layers occurred, followed by formation of the hexagonal Pd2Ge phase. This hexagonal phase then transformed into orthorhombic PdGe, followed by solid state epitaxial growth of Ge at the contact / GaAs interface. The kinetics of the solid state reactions, which occur during ohmic contact formation, were determined by measuring the grain growth rates associated with each phase from the videotape observations. These data agreed with a previous study that measured the activation energies through a differential scanning calorimetry (DSC) method. We established that the Ge transport to the GaAs interface was dependent upon the grain size of the PdGe phase. The nucleation and growth of this phase was demonstrated to have a significant effect on the solid phase epitaxial growth of Ge on GaAs. These findings allowed us to engineer an improved two step annealing procedure that would control the shape and size of the PdGe grains. Based on these results, we have established the suitability of combining FIB sample preparation with in-situ cross-sectional transmission electron microscopy (TEM) annealing for studying thin film solid-state reactions.
Electron Microscopy of Single Molecules
Authors: Luzzi D.E. , Smith B.W. 
Published: April 2011

AbstractWe report on the imaging of single C60 molecules adsorbed on the surface of carbon nanotubes. In the course of the work, the efficacy of carbon nanotubes as substrates for the high signal-to-noise observation of molecules is examined. The stability of nanotubes as a function of temperature, chemical environment and irradiation environment is explored. Carbon nanotubes are found to have a threshold energy for ballistic irradiation damage of approximately 85 keV. Finally, the use of nanotubes as in-situ reaction chambers and for other in-situ experimentation is demonstrated.
Combined HRTEM and EFTEM Study of Precipitates in Tungsten and Chromium-Containing TiB2
Authors: Mader W. , Freitag B. , Kelm K. , Telle R. , Schmalzried C. 
Published: April 2011

AbstractThe structure and chemical composition of two types of precipitates in the system TiB2-WB2-CrB2 were studied by means of high-resolution TEM and energy filtering TEM. Type I particles (W2B5 structure) are precipitated at the basal plane of the hexagonal matrix whereas type II precipitates are thin platelets lying parallel to the {1100} prism planes. Lattice imaging yields displacements of the metal positions with respect to the matrix. Information on the chemical composition at high lateral resolution is obtained from elemental maps of all chemical constituents using electron spectroscopic imaging (ESI). The type II precipitates show a decrease in the B and Ti concentration, whereas the tungsten concentration increases and the Cr is homogeneously distributed. The HRTEM results combined with the results of the elemental maps allow to develop a structural model based on the intergrowth of the β-WB structure in the TiB2-rich matrix. The two deficient boron layers in W0.5Ti0.5B with a spacing of 0.38 nm can be used to examine the resolution limit of ESI.
Microstructural Characterization of Longitudinal Magnetic Recording Media
Authors: Sinclair Robert , Park Dong-Won , Habermeier Claus , Ma Kai 
Published: April 2011

AbstractThe optimization of disc manufacturing conditions is required to increase the storage capacities of magnetic recording media, which is strongly related to both magnetic properties and microstructural features. Analyzing the microstructure requires transmission electron microscopy (TEM), since the small grain sizes of the media prevent other tools from characterizing them. This paper discusses several fascinating characteristics of TEM in understanding and analyzing the properties of the recording media.
Synthesis of Multiwalled Carbon Nanotubes
Authors: Jacques David , Villain Stephane , Rao Apparao M. , Andrews Rodney , Derbyshire Frank , Dickey Elizabeth C. , Qian Dali 
Published: April 2011

ABSTRACTIn a recent publication we have described the synthesis of multiwalled carbon nanotubes (MWNTs) by the reaction of a hydrocarbon vapor over a dispersed iron catalyst that is deposited in situ on quartz substrates. Our system configuration involves entraining a mixture of xylene and ferrocene into an inert gas stream. Decomposition of the ferrocene at temperatures in the range 625-775 °C, and at atmospheric pressure, produces a coating of iron nanoparticles on the quartz surfaces, and these metal sites function as catalysts for the formation and growth of MWNTs. In this study, we report the influence of operating conditions on MWNT purity and yield. These parameters include the feed injection temperature, furnace temperature, hydrocarbon partial pressure, reaction time, space velocity, and iron to carbon ratio in the feed. We observed that the quality of the MWNTs dependc sensitively on the growth parameters and a window for the operating conditions is identified for the growth of high purity aligned MWNTs. Characterization of the MWNTs by electron microscopy has shown that there is a relationship between metal particle size and MWNT diameter.
Synthesis of Novel Mesoporous Carbons and Their Applications to Electrochemical Double-Layer Capacitors
Authors: Hyeon Taeghwan , Oh Seung M. , Lee Jinwoo , Yoon Songhun 
Published: April 2011

ABSTRACTWe have developed a new synthetic procedure to fabricate mesoporous carbons using mesoporous inorganic materials as templates. Mesoporous carbons with regular 3-dimensionally interconnected ∼ 2 nm pore arrays have been synthesized using aluminum substituted MCM-48 and HMS mesoporous silicas as templates. The polymerization of phenol and formaldehyde inside the nanopores of the mesoporous silica templates generated phenol-resin/luminosilicate nanocomposites. The carbonization followed by the removal of silicate templates generated mesooporous carbons with regular pore dimensions. The mesoporous carbons exhibited excellent performance for electrochemical double layer capacitors (EDLC). They revealed ideal rectangular shaped cyclovoltammograms up to the high scan rate of 20 mV/sec, which is important for the future applications.
Synthesis of C60 Chains Contained Within Carbon Nanotubes
Authors: Smith Brian W. , Luzzi David E. 
Published: April 2011

ABSTRACTWe have recently discovered self-assembled chains of C60 molecules contained within single wall carbon nanotubes (SWNTs). Using in situ transmission electron microscopy studies, we show a route by which such ‘peapod’ structures can be synthesized. The results indicate that exterior C60 molecules arrive at the nanotubes from the vapor phase and subsequently enter, presumably through open ends or sidewall defects. The methods discussed in this work provide a means for the bulk production of these molecular assemblies.
Field Emission and Nanostructure of Carbon Films
Authors: Merkulov V. I. , Lowndes D. H. , Baylor L. R. 
Published: April 2011

ABSTRACTThe results of field emission measurements of various forms of carbon films are reported. It is shown that the films' nanostructure is a crucial factor determining the field emission properties. In particular, smooth, pulsed-laser deposited amorphous carbon films with both high and low sp3 contents are poor field emitters. This is similar to the results obtained for smooth nanocrystalline, sp2 - bonded carbon films. In contrast, carbon films prepared by hot-filament chemical vapor deposition (HF-CVD) exhibit very good field emission properties, including low emission turn-on fields, high emission site density, and excellent durability. HF-CVD carbon films were found to be predominantly sp2 -bonded. However, surface morphology studies show that these films are thoroughly nanostructured, which is believed to be responsible for their promising field emission properties.
Filtered Cathodic Arc Deposited Diamond-Like Carbon: Electron Spin Resonance (ESR) and Raman Spectroscopy
Authors: Druz B. , Zaritskiy I. , Yevtukhov Y. , Konchits A. , Valakh M. , Kolesnik S. , Shanina B. , Visotski V. 
Published: April 2011

ABSTRACTTetrahedral diamond like carbon (ta-C) films were deposited onto Si substrates using Filtered Cathodic Vacuum Arc (FCVA) process. Stress of deposited films was varied in the range 3.5÷8.5 GPa. The ESR (stationary and pulse) and Raman techniques were used to analyze sp2 related defects in the pseudo-gap of undoped, as deposited 20 – 100 nm thick films. The results are compared with data for direct ion beam deposited from CH4 plasma hydrogenated DLHC films and nature of paramagnetic defects in DLC is discussed.