bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion of Implanted Nitrogen in Silicon at High Doses
Authors: Adam Lahir Shaik , Robertson Lance , Law Mark E. , Jones Kevin , Gable Kevin , Hegde Suri , Dokumaci Omer
Published: April 2011

Nitrogen implantation is used to retard gate oxide growth thereby making it particularly usefulfor dual- VT and System On A chip technologies. This paper discusses the diffusion behavior and the concomitant defect evolution at high doses of implanted nitrogen in silicon. This paper shows that as the nitrogen implant dose is increased, the extent of nitrogen diffusion reduces. This paper also reports based onTEM studies, that upon annealing at 750°C, 5 × 10014 N2+/cm2, 40 keV implant produces Type I extended defects. However, 2 × 1015 N2+/cm2, 40 keV implant, produces a continuous amorphous layer to a depth ofabout 800 to 900 Å from the surface. In addition, upon annealing at 750°C, the 2 × 1015 N2+/cm2, 40 keV implant produces Type V or solid solubility defects in addition to End of Range or Type II defects.
Modeling of Boron Implantation Into Si With Decaborane Ions
Authors: Insepov Zinetulla , Sosnowski Marek , Yamada Isao
Published: April 2011

A molecular Dynamics (MD) model of B implantation into Si and of sputtering the Si surface withenergetic B10 clusters has been developed. The goal was to simulate the implantation of ions of decaborane (B10H14), which may become an important process for the formation of ultra shallow junctions in future MOS devices. The simulations, carried out for the cluster ion impact energy from 3.5 keV to 15 keV, have revealed the formation of a large amorphized region in a subsurface region. At low cluster impact energies in this range some of the B atoms were recoiled back from the surface, but at the energy of 12 keV and above almost all of the Boron atoms were successfully implanted into Si. The sputtering yield of Si has been also computed and found to increase with energy, reaching the value of 6 Si atoms per B10 cluster at 15 KeV. The number of displaced surface atoms correlates well with the sputtering yield, and between 3.5 and 10 keV it has a non-linear dependence on energy. At higher energies the number of displaced atoms increases linearly with energy, in agreement with the Khinchin-Pease formula [9]. The sputtering yield at 12 keV was also measured by the amount of Si removed by a decaborane beam from a thin Si film deposited on a carbon substrate. The predicted sputtering yield agrees well with this experiment.
Modeling of Annealing of High Concentration Arsenic Profiles
Authors: Fastenko Paevl , Dunham Scott T. , Henkelman Graeme
Published: April 2011

Understanding the diffusion and activation of arsenic is critical for the formation of low resistance ultra-shallow junctions as required for nanoscale MOS devices. In this work, we use results of ab-initio calcultions in order to gain insight into the fundamental process involved in arsenic activation/deactivation. Utilizing continuum modeling, we find it is possible to account for both the very rapid initial deactivation of arsenic as well as the strongly superline independence of interstitial supersaturation on doping level which accompanies deactivation. The critical process is the rearrangement of A s-atoms via in testitial mediated diffusion leading to ejection of silicon atoms from arsenic complexes and formation of arsenic-vacancy clusters.
Lattice site location of ultra-shallow implanted B in Si using ion beam analysis
Authors: Kobayashi Hajime , Nomachi Ichiro , Kusanagi Susumu , Nishiyama Fumitaka
Published: April 2011

We have investigated the lattice site location of B in Si using ion channeling in combination with nuclear reaction analysis (NRA). Silicon samples implanted with Boron at an energy of 10 keV and a dose of 5 × 1014 cm−2 (low dose samples) or 5 × 1015 cm−2 (high dose samples) were annealed at 1000 °C for 10 seconds (RTA) or at 800 °C for 10 minutes (FA). The activation efficiencies of these samples were estimated from the B atomic concentration and the hole concentration obtained by secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP), respectively. We also studied the ion implantation damage of Si crystals using ion channeling combined with Rutherford backscattering spectrometry (RBS). We found that the activation efficiency is proportional to the substitutionality, meaning that substitutional B is fully activated without any carrier compensation. We also found that B atoms go to the substitutional sites and are activated up to the solubility limit in the high dose samples. However, the ion implantation damage of the crystalline Si in the high dose samples increases somewhat after annealing.
Silicon Interstitial Driven Loss of Substitutional Carbon from SiGeC Structures
Authors: Carroll M. S. , Sturm J. C. , Napolitani E. , Salvador D. De , Berti M. , Stangl J. , Bauer G. , Tweet D. J.
Published: April 2011

The effect of annealing silicon capped pseudomorphic Si0.7865Ge0.21C0.0035 or Si0.998C0.002 layers on silicon substrates in nitrogen or oxygen at 850°C was examined using x-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS). Most substitutional carbon is lost from the alloy layers due to carbon out-diffusion rather than from precipitation. The carbon is found to diffuse more rapidly out of the SiGeC layer than the SiC layer after nitrogen and the carbon is found to leave the sample entirely, an effect that is enhanced by oxidation and thin cap layers. All substitutional carbon can be removed from the sample in some cases implying negligible formation of silicon-carbon complexes. Furthermore, it is found that each injected silicon interstitial atom due to oxidation causes the removal of one additional carbon atom for the SiGeC layer.
Rotational Averaging of Material Removal During CMP
Authors: Evans David R. , Oliver Michael R.
Published: April 2011

At present, several different competing mechanical configurations are used in chemical mechanical polishing. These range from classical rotary designs to orbital and linear systems, as well as the more recent web format. Invariably, wafer rotation is used in all of these systems to average out gross material removal rates and improve within wafer thickness uniformity. Although this might appear to be trivial and unworthy of serious investigation, in reality the interaction of polishing pad surface structure, along with whatever abrasive particles and chemical agents that might be present is quite complex. In addition, fluid transport between wafer and pad surfaces is strongly affected by pad macrostructure and relative motion of the two surfaces.
Oxide Powders for Chemical Mechanical Polishing Produced by Chemical Vapor Synthesis
Authors: Sieger H. , Winterer M. , Keiderling U. , Hahn H.
Published: April 2011

Ultrafine silica, alumina and doped alumina/silica powders have been produced by Chemical Vapor Synthesis (CVS). Primary particle sizes from 3.5 to 12.4 nm have been achieved. Agglomerate sizes ranging from approx. 10 to 150 nm have been achieved in aqueous dispersions.
Effects of Particle Concentration in CMP
Authors: Choi Wonseop , Lee Seung-Mahn , Singh Rajiv K.
Published: April 2011

This paper reports on characterization of the surface coverage of particles by in-situ lateral friction force measurement during chemical mechanical polishing. The lateral friction force apparatus was made to operate close to real CMP conditions. For these experiments a sapphire wafer of constant surface roughness was used. For both 2psi and 4psi down force we observed increase in lateral friction forces with increasing solid loading. The lateral friction forces have been found to be significantly dependent on the contact area at the wafer-pad-slurry interface, thus showing that in-situ dynamic friction force changes in the surface coverage of particles. From these results, we conclude that the enhancement of frictional force is due to increased contact area at the wafer-pad-slurry interfaces. The lateral friction force measurement can provide an understanding of wafer-pad-slurry interactions.
Layout Pattern Density and Oxide Deposition Profile Effects on Dielectrics CMP
Authors: Park Young B. , Kim Joon Y. , Seo Dae W.
Published: April 2011

Test mask for characterizing pattern dependent variation of the remaining thickness after chemical-mechanical polishing (CMP) was designed with taking the experimentally obtained interaction distance into consideration. Measured interaction distance was constant independent of pattern variables such as pattern density and pattern shapes between line and area. And systematic exploration regarding pitch effects on remaining nitride thickness in STI (Shallow Trench Isolation) CMP was performed with comparing PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) and HDP (High Density Plasma) oxide. Both measured remaining nitride thickness and expected oxide pattern density from consideration of deposition profile effects showed a good correlation with respect to pitch variation for a constant layout pattern density.
Mechanisms of Post-CMP Cleaning
Authors: Liang H. , Estragnat E. , Lee J.
Published: April 2011

We investigate the post-CMP cleaning process with a tribological approach. A cleaning process involves three components: brush, wafer/disk, fluid undergoing three-body sliding contact between the brush, wafer, and particles from slurry. Having this in mind, we investigated cleaning mechanisms through experimental measurement of friction force and analyzed the contact condition for particle removal. Our investigation leads to the conclusions that the cleaning process is a boundary to elastohydrodynamic lubricating process that involves a constant contact between a brush and the wafer or disk surface. The motion of the brush nodule is such that the surface forces between the brush and workpiece change from an initial adhesion to sliding abrasion. These analysis leads to insight of particle removal mechanisms.
Rapid adatom island decay on Cu(111): a kinetic Monte Carlo simulation study
Authors: Larsson Mats I.
Published: April 2011

Kinetic Monte Carlo (KMC) simulations are used to investigate the recent scanning tunneling microscopy (STM) measurements of fast decaying adatom islands on Cu(111). The KMC model is a full diffusion bond-counting model including nearest neighbor as well as second-nearest neighbor interactions. For encounters between steps in adjacent atomic layers of an island it is demonstrated that a moderately reduced activation energy for interlayer adatom transport is enough to obtain correspondence between simulations and experiments, provided that the one-dimensional Ehrlich-Schwoebel barrier for corner transitions is reduced to zero. The results presented in this report are interesting because they demonstrate that step-edge crossing by simple adatom hopping is sufficient to explain the rapid island-decay mechanism.
Simulation Study of Copper Cluster Deposition
Authors: Kang Jin C. , Kang Jeong W. , Hwang Ho J.
Published: April 2011

The ionized cluster beam deposition of Al and Cu clusters has been investigated with a classical molecular dynamics simulation and the Metropolis Monte Carlo simulation. The spreading of the cluster has been studied as functions of cluster size and initial cluster energy. When the local area reached local melting spot on the surface, around the impact point of an energetic cluster, during a few ps, intermixing was easily achieved and a good epitaxial film with optimum bulk density was formed. For uniform film growth using cluster impact, it is necessary to make the local area temperature higher than melting temperature on the surface around the impact point of an energetic cluster.
Study of Atomic Steps on the Single Crystal Surface by Grazing Ion Scattering
Authors: Dzhurakhalov A.A.
Published: April 2011

The features of the correlated glancing scattering of medium energy ions by the imperfect surface of a single crystal have been investigated by computer simulation It has been shown that, from the correlation of the experimental and calculated energy distributions of the scattered particles, one may determine a spatial extension of the isolated atomic steps on the single crystal surface damaged by the ion bombardment. The presence of atomic steps on the surface lead to increase of the capture probability of channeling ions in the layers under the steps and to increase of probability of their dechanneling. The obtained computer simulation results show that dechanneled ions form characteristic peaks in the angular and energy distributions of scattered particles. Character of ions movement under the step (their ranges, energy losses and dechanneling) is determined both the grazing angle and capture angle under the step.
Crystallographic and morphological properties of magnetron sputtered Ti and Zr thin films
Authors: Chinaglia Eliane F. , Oppenheim Ivette C.
Published: April 2011

Crystallographic and surface morphological characteristics of polycrystalline hcp Ti and Zr thin films were studied as a function of the homologous substrate temperature TS/TM and the thickness t of the films (28 nm ≤ t ≤ 380 nm). TS is the substrate temperature during deposition and TM is the melting point of the film's material. For the whole range of considered temperatures (0.14 ≤ TS/TM ≤ 0.48) Zr films presented a {0002} crystallographic orientation. As TS/TM increased, Ti films suffered a transition from a columnar grain structure with {0002} preferential crystallographic orientation to a cone-like-shape grain structure with {1011} preferential crystallographic orientation. Our results suggest that Zr films suffer a structural transition from Zone T to Zone II at temperatures similar to those predicted by Thornton's Structure Zone Model for thick films while Ti films do not have a microstructure typical of Zone II even for relatively high values of TS/TM, presenting a transition from Zone I to Zone T in the studied range of temperatures.
A Study on unique Crystal Morphology observed in the Polycrystalline Copper CVD
Authors: Chang Yuneng , Chen Yalian , Chen Kuanhon
Published: April 2011

Nanostructure copper whisker growth was observed in an atmospheric pressure chemical vapor deposition (CVD) system, which used copper acetylacetonate vapor and 10-15 torr of water vapor as reactants, with 0.04-0.10 torr of chromium acetylacetonate vapor added as growth promoting catalyst. Water vapor initiated nucleation of these helical, spiral shape Cu(111) and (200) polycrystalline whiskers. While chromium acetylacetonate accelerated the growth rate. Copper whiskers had radii from 0.1 to 0.24 μm, lengths from 1 to 10 μm, and distribution density of 0.20-3.6 whiskers/μm2. Dependence of such whisker characteristics on temperature, partial pressures of H2O and chromium acetylacetonate was used to construct a kinetic model. From the Arrhenius equation, data analysis for whisker growth rate against deposition temperature showed that the activation energy for whisker growth along radial direction is 12.4 kcal/mol, and 19.6 kcal/mol for growth along axial direction. Based on such data and SEM observations, a base vapor-liquid-solid (VLS) model involving BCF theory was proposed to describe the governing mechanism for the axial growth. This model interpreted the competitive growth phenomena in both radial and axial directions, and controlling steps for radial and axial growth being assigned to mass transfer and surface reaction, respectively.
Effects of Non-Planar Surfaces on the Growth of RF Magnetron Sputtered ZnO
Authors: Holland A.S. , Reeves G.K. , Leech P.W.
Published: April 2011

This paper describes the influence of the topography of a lithographically patterned substrate (aluminium electrodes on a CVD diamond film) on the uniformity of sputtered ZnO films. Diamond films with an average surface roughness of ∼1nm, had aluminium electrodes (thickness 80nm, linewidth/space 2.6μm) patterned on them. ZnO was RF sputtered on to the substrate and the uniformity of the ZnO grain structure was examined using SEM, XRD and AFM. Abrupt changes in topography at the edges of the aluminium electrodes resulted in poor alignment of ZnO grains. SEM/AFM micrographs show misalignment of ZnO grains at the edges of the raised electrodes. When the electrodes were recessed into the diamond film, using a damascene-like process, the SEM/AFM micrographs showed improved grain uniformity of ZnO. XRD showed a significant increase in the c-axis (002) orientation and an absence of the (101) orientation. AFM micrographs also showed the improvement in the ZnO surface topography. These results may be of significance to high frequency Surface Acoustic Wave (SAW) devices.
Preparation and characterization of (Ba,Sr)TiO3 thin films by liquid source chemical vapor deposition
Authors: Yang Cheol-Hoon , Han Young-Ki , Kim Dong-Hyun , Han Geun-Jo , Yang Doo-Young , Oh Ki-Young , Song Juho , Park Jaehoo , Hwang Cheol-Seong
Published: April 2011

The cocktail source of BST was prepared by mixing of Ba, Sr, and Ti precursor solution with specific mole ratio. This cocktail source was vaporized and delivered into the warm wall reactor by liquid delivery system(LDS) and gaseous source was distributed by simple structure of gas injector instead of showerhead system. The thickness uniformity of BST on 8 inch wafers were less than 3%. The Ti composition uniformity of our films were less than the 1 at%(1σ ) at stoichiometric and near stoichiometric. Their dielectric constant was about 230 and leakage current density was lower than 10-8 A/cm2 under ±1V bias. Excellent step coverage and smooth (haze-free) surface morphology of BST films were obtained by a deposition using a noble dome type reactor. The merit of our warm wall type reactor also will be explained by excellent step coverage and the uniform composition with 3 dimensional structure. Our achievement should be applicable to the capacitor of next generation DRAM.
Evolution of Coherent InAs Quantum Dots Above the Coherent Critical Thickness Window by Metalorganic Chemical Vapor Deposition
Authors: Yeoh T. S. , Liu C. P. , Kim Y. W. , Coleman J. J.
Published: April 2011

InAs quantum dots were grown on GaAs substrates at various coverages and capped after varying the time of growth interruption. The evolution of this system was examined by correlating photoluminescence and transmission electron microscopy measurements. Results show for the first time the growth interruption to be a critical factor in generating defect-free quantum dot ensembles at coverages well above established metalorganic chemical vapor deposition coverage window for defect-free, Stranski-Krastanow self-organized growth. In addition, our results also support the absence of a stable, dislocation free 3D state and that the chemical potential eventually drives the system towards dislocated quantum dot clusters.
Synthesis of Tin Oxide Thin Films by Pulsed Laser Deposition Using SnO2Targets
Authors: Suda Yoshiaki , Kawasaki Hiroharu , Doi Kazuya , Nanba Jun , Wada Kenji , Ebihara Kenji , Ohshima Tamiko
Published: April 2011

Tin oxide (SnO2) thin films have been grown on Si (100) and Al2O3 substrates by pulsed Nd:YAG (532nm) and KrF excimer (248 nm) laser deposition methods using SnO2 targets. X-ray diffraction measurement showed that the almost amorphous microstructure transformed into a crystalline SnO2 phase and preferred orientation varied from (101) to (110) on Si (100) with increasing oxygen gas pressure. This result suggests that oxygen gas pressure affects the phase formation, crystalline structure and preferred orientation of the films. Gas sensing properties of SnO2 thin films by PLD method were also investigated over the temperature range 300 – 600°C, using 0.31vol%H2 as a test gas. The oxygen gas pressure results in a notable change in gas sensing properties of SnO2 thin films.
Microstructure Origin for Thermal Fatigue of TiNi Films
Authors: Wen Shulin , He Jibao
Published: April 2011

In order to improve the performance and prolong the life of shape memory alloy material (SMA), it is very important to trace and study the microstructure change on the fatigue of SMA. The microstructure features between the samples before and after thermal fatigue (about 100,000 thermal cycles) of the NiTi-SMA films were examined and compared with each other by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). It was found that there is no difference of microstructures between the two kinds of samples except some precipitates appeared in the fatigue specimen. These precipitates which may be identified as TiNi3phase with a grain size of 10-20 nm may impede transformation from martensite to austenite which works as mechanism of SMA during thermal fatigue. Therefore, these precipitates result in the serious decay on SMA performance and further fracture of the SMA material.
Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process
Authors: Muratore Chris , Moore John J. , Rees J. Alan , Carter Dan , Roche Greg
Published: April 2011

Measurement of the ion energy distributions (IED's) of N2+ ions produced in an inductively coupled plasma (ICP) source revealed that adding argon to the nitrogen gas before excitation in the source increased the nitrogen ion current. Adding helium resulted in an increase of the most probable ion energy, and a higher-energy component of the N2+ IED at about 20 eV. Preliminary calculations of the electron energy distributions (EED's) correlate well to the IED's for both inert gas additions. Experiments were performed to determine the effect of these modified energy distributions of the reactive species on titanium nitride thin film growth rates, microstructure and mechanical properties. Deposition experiments were conducted using the ICP source and an unbalanced magnetron with a titanium cathode. Results showed that the argon inert gas addition resulted in increased deposition rate and reduced 3-D features. Film roughness was decreased to 1.61 nm from 2.05 nm when helium was mixed with the nitrogen. Mixing both argon and helium with the nitrogen yielded combined effects of deposition rate increase, reduced 3-D features and increased smoothness. The inert gas additions increased hardness of the TiN films from 17.3 GPa to 21.1 GPa with the argon addition and to 25.0 GPa with the helium addition
Texture Evolution in Al(Cu) Interconnect Materials
Authors: Murray C.E. , Rodbell K.P.
Published: April 2011

An investigation of the microstructural evolution of Al(Cu) thin films deposited on a variety of interlevel dielectric (ILD) layers was performed. A combination of X-ray texture measurements and scanning electron microscopy (SEM) was employed to link the texture behavior of the as-deposited Al(Cu) films at different thicknesses to the observed morphological development within the films. Three regimes of texture were revealed, corresponding to (1): Al(Cu) island growth and individual island coalescence, (2): fully coalesced film and the onset of grain growth and (3): extensive grain growth. The first and last of these regimes exhibited offset (111) texture, in which the maximum diffracted intensity from Al (111) is offset from the substrate normal. However, the position of maximum offset texture differed between the first and third stages of growth, indicating that two different mechanisms were responsible. The offset (111) texture observed in the third regime of Al(Cu) film microstructure was due to the faceting of grain surfaces. The time required for the films to reach these three stages depended on the effective diffusivity of the Al atoms on the ILD surfaces, which differed in chemistry and topography.
Crystallographic Texture Characterization of Inlaid Copper Interconnects
Authors: Zienert Inka , Besser Paul , Blum Werner , Zschech Ehrenfried
Published: April 2011

Developing faster integrated circuits places incredible demands on the interconnect system. The smaller feature sizes lead to excessive current densities, which in turn make the interconnect lines more susceptible to electromigration (EM) failure.[1] Studies have shown that EM performance can be improved by increasing the strength of the {111} texture in conventionally- fabricated aluminum-based lines.[2-6] The strong {111} texture minimizes the presence of high- angle grain boundaries along the interconnect line, thus minimizing a fast-diffusion path for EM mass transport.[2-4,7-12]
Room-Temperature UHV-Deposited Titanium Monoxide Films on Oxidized Polycrystalline Copper
Authors: Fuenzalida V. M. , Grahmann C. R. , Herrera C. , Zárate R. A. , Avila C. , Pilleux M.E.
Published: April 2011

Polycrystalline copper films thicker than 100 nm were evaporated on silicon wafers with their native oxide under ultrahigh vacuum conditions leading to an rms roughness of ~2 nm of the copper film. X-ray photoelectron spectroscopy (XPS) revealed a clean copper surface with only traces of oxygen. The samples were exposed to air, leading to an oxide film consisting of CuO. TiO films were subsequently deposited onto the oxidized copper films from a resistively heated tungsten boat with the substrate at room temperature. The TiO films exhibited good adherence and were amorphous. XPS measurements revealed that the TiO films were contamination-free and that the first layers of TiO reduced the thin native oxide of the copper substrate from Cu(II) into Cu(I) or Cu(0) and transformed the TiO into TiO2 at the interface.
A Surface Insulator-to-Conductor Phase Transition in Colossal Magnetoresistive Manganese Perovskites Thin Films
Authors: Borca C.N. , Xu Bo , Komesu Takashi , Jeong Hae-Kyung , Liou S.-H. , Dowben P.A.
Published: April 2011

We have observed a distinct surface phase transition for an important class of colossal magnetoresistive materials, La0.65D0.35MnO3 (with D = Sr, Pb) occurring in a surface layer compositionally different from the bulk. The surface phase transition occurs around 240 K compared to350 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic ‘bad metal’ occurs, while the lower-temperature surface transition is from an n-type (in case of La0.65D0.35MnO3) or a p-type (in case of La0.65D0.35MnO3) semiconductor to a semimetal with increasing temperature.
Magnetic characterization of (001) and (111) Ni films epitaxially grown on MgO
Authors: Lukaszew R. A. , Stoica V. , Clarke R.
Published: April 2011

One interesting application of epitaxial magnetic thin films is to use them as one of the electrodes in a spin-dependent tunneling junction, in order to use the magnetocrystalline anisotropy to define the required two states of the magnetization. [1] In our preliminary work, we prepared epitaxial magnetic films on copper buffer layers grown on silicon substrates. [2] The single crystalline quality of the films was particularly evident in the magnetization hysteresis loops, showing a sharp reversal at fairly high fields (120 Oe), when the samples were magnetized along the crystallographic easy axis. One technological disadvantage in this type of samples is the chemical interaction between the metallic layers and the silicon substrate.

In order to explore the possibility of epitaxial magnetic films on less reactive substrates, we studied the growth on MgO substrates. We have shown that it is possible to obtain epitaxial (001) and (111) Ni films grown on MgO substrates. [3] In particular we observed that the crystalline quality of the films improved considerably after 10 nm of film growth. We will now present our studies on the magnetic properties of these films, particularly the azimuthal dependence of the magnetization reversal using MOKRE, correlating our finding with the structural characterization obtained with RHEED, STM and XRD.
Magnetic Properties and Scaling Behavior in Perovskite–like La0.7(Ba1−xPbx)0.3CoO3 System
Authors: Chen Chiung-Hsiung , Huang Ting-Sheng , Tai Ming-Fong
Published: April 2011

In this study, we used x-ray diffraction patterns and dc magnetic measurements to investigate the crystallographic structure, magnetic properties and scaling behavior of the distorted perovskite La0.7(Ba1−xPbx)0.3CoO3 (0 ≤ x ≤ 0.5) system with a constant ratio of Co4+/Co3+. Samples with x = 0.0 and 0.1 were crystallized in the cubic structure with a ∼ 7.76 Å whereas samples with x ≥ 0.2 were crystallized in an orthorhombic Pbnm space group with a ∼ b ∼ 5.50 Å and c ∼ 7.85 Å. For all our samples the spin-glass-like behavior were observed in low temperature and low field ranges. The Pb2+ substitution on Ba2+ site does not significantly affect the ferromagnetic transition temperature TC, but does introduce large variation in the magnetic strength. In both the ferromagnetic and paramagnetic states the minimum values of the average effective moments provided by every Co ion occur at x = 0.3. We also observed the scaling behaviors of magnetic data in all samples. The derived values of the critical exponents (β, γ, δ) were consistent with those predicted by mean field theory and a three-dimensional Heisenberg model.
A Landau-Ginzburg Description of Sb Overlayers
Authors: Skomski R. , Komesu T. , Jeong H.-K. , Borca C. N. , Dowben P. A. , Ristoiu D. , Nozieres J. P.
Published: April 2011

The spin polarization of Sb overlayers on the semi-Heusler alloy NiMnSb is investigated in terms of the Landau-Ginzburg approach. The half-metallic semi-Heusler alloy NiMnSb acts as a ferromagnetic perturbation and induces a spin polarization in the semimetallic Sb overlayer. Using a Gaussian approximation, the propagation of the spin perturbation in the overlayer is calculated. The results are compared with spin-polarized inverse photoemission spectroscopy (SPIPES) results and with recent spin-dependent envelope-function approximation (SDEFA) predictions. The Landau-Ginzburg parameters are both band-structure and temperature dependent, and it is argued that thermal spin excitations lead to an injection depth decreasing as 1//T law at high temperatures.
Spontaneous Ac Field Induced Mechanical Rotation in Magnetostrictive Fesib-Based Wires Subjected to Thermal Treatments
Authors: Raposo V. , Mitra A. , Vázquez M.
Published: April 2011

An astonishing new phenomenon has been recently observed in magnetic wires. It consists of the spontaneous rotation of the wires when submitted to an exciting AC axial field with frequency of the order of kHz and amplitude above some threshold. The rotation is believed to appear due to interaction between generated magnetoelastic standing waves and induced eddy currents. In the present work rotational characteristics of Fe77.5Si7.5B15 and Fe73.5Si13.5B9Cu1Nb3wires in their as-cast amorphous state and after heat treatments leading to devitrification has been investigated. It is proved that this rotational phenomenon is only observed in samples with large enough magnetostriction irrespective of their structural character. Moreover, changes in rotational characteristics are ascribed to the structural modifications accompanying the devitrification process.
Domain Structure of ‘Thick’ Amorphous Microwires with Nearly Zero Magnetostriction
Authors: Chiriac Horia , Óvári Tibor-Adrian , Takajo Minoru , Yamasaki Jiro , Zhukov Arcady
Published: April 2011

Nearly zero magnetostrictive glass-coated amorphous microwires are suitable materials for sensor applications. Samples with metallic core diameters below 20 [.proportional]m exhibit almost nonhysteretic BH loop, related to the existence of a domain structure with azimuthal easy axis. The magnetic behavior of these microwires is changing drastically when the metallic core diameter increases over 25 [.proportional]m, i.e. they display a bistable magnetic behavior at low fields, that is a one step magnetization reversal at a certain value of the applied field, called switching field. Results on the direct domain observation in nearly zero magnetostrictive Co68.25Fe4.5Si12.25B15 glass-coated amorphous microwires by means of Kerr microscopy are reported for the first time. The effect of glass removal on the domain structure has been also studied. AC hysteresis loop measurements have been employed to establish a correlation between domain structure and magnetic behavior.

Glass-coated microwires exhibit a single domain configuration with the magnetization pointing mostly to the wire axis. The domain structure does not change qualitatively after glass removal, but the parameters of the squared hysteresis loops are modified. The remanence to saturation ratio increases after glass removal, while the switching field decreases.

The obtained results are of interest for sensor applications, and show that the metallic core diameter is a dimensional factor that contributes to important changes in the domain structure and magnetization process of such microwires.
Progress of the Phase-change Optical Disk Memory
Authors: Ohta Takeo , Yamada Noboru , Yamamoto Hiroaki , Mitsuyu Tsuneo , Kozaki Takashi , Qiu Jianrong , Hirao Kazuyuki
Published: April 2011

Optical memory has two recording modes: the photon-mode as a silver halide photograph and the heat-mode as a laser optical disk. Though laser heat-mode recording has the advantage of environmental stability, it has limitations due to thermal diffusion phenomena, which will be discussed in this paper.
Incorporation of Hydrogen and Oxygen into (t)a-C:H Thin Films Deposited using DECR plasma (*)
Authors: Piazza Fabrice , Grambole Dieter , Herrmann Folker , Relihan Gary , Barthe Marie France , Desgardin Pierre , Golanski André
Published: April 2011

A distributed electron cyclotron resonance (DECR) plasma reactor powered by a microwave generator operating at 2.45 GHz (800 W) was used to deposit (t)a-C:H thin films at RT on <100> Si substrates RF biased within the range 25≤|V0|≤600 V.C2H2 was used as precursor. The plasma pressure was varied within the range 0.1≤P≤1.5 mtorr. The films were analysed using spectroscopic ellipsometry (SE) and Fourier transform infrared (FTIR) spectroscopy. The hydrogen content NH and the density of the films were determined from nuclear reaction analysis (NRA) using the resonance at 6.385 MeV of the reaction: 15N + 1H → 12C + 4He + γ. Positron annihilation spectroscopy was used to detect the porosity. The evolutions of NH as a function of the substrate ion current density n+ and as a function of V0 show that the hydrogen incorporation results from the competition between chemisorption and deposited energy density related effects. The increase of the hydrogen incorporation leads to a decrease in the film density and a lower deposition rate. The porosity of the films deposited at low pressure (∼0.1 mTorr) with V0= −80 V has been detected. The comparison between results of SRIM-2000 simulations and the evolution of NH as a function of V0 shows that the porosity and the hydrogen content are not correlated. The absorption of oxygen and nitrogen for the low density films has been detected from the observation of the 3250–4000 cm-1infra-red (IR) band.
Preparation and properties of amorphous carbon oxynitrides a-CNxOy films made by a nitrogen radical sputter method and by the layer-by-layer method
Authors: Naruse Yohko , Nitta Shoji , Habuchi Hitoe
Published: April 2011

We have tried to prepare amorphous carbon oxynitrides (a-CNxOy)films by the oxygen radical treatment (ORT) of amorphous carbon nitrides (a-CNx) and also by the layer-by-layer method. Properties of a-CNxOy films were studied with X-ray photoelectron spectroscopy (XPS), photothermal deflection spectroscopy (PDS), ultraviolet-visible (UV-VIS) optical transmittance spectra, Raman spectra and electron spin resonance (ESR). Oxygen radical affects to a-CNx by etching, termination of defects and oxidation. A-CNxOy films are interesting for the application to luminescent materials and also to low dielectric consta nt materials.
A Model to Interpret the Raman Spectra of Disordered, Amorphous and Nanostructured Carbons
Authors: Ferrari Andrea Carlo
Published: April 2011

Raman spectroscopy is a very popular, non-destructive tool for the structural characterisation of carbons. Raman scattering from carbons is always a resonant process, in which those configurations whose band gaps match the excitation energy are preferentially excited. The Raman spectra of carbons do not follow the vibration density of states, but consist of three basic features, the G and D peaks around 1600 and 1350 cm-1 and an extra T peak, for UV excitation, at ∼980–1060 cm-1. TheRaman spectra at any wavelength depend on 1) clustering of the sp2 phase, 2)bond length and bond angle disorder, 3) presence of sp2 rings or chains, and 4) the sp2/sp3 ratio. It will be shown how the basic features of the Raman spectra vary by rationalising them within a three-stage model of order of carbons. It is shown how the three-stage model can account for the vast range of experimental data available for Raman experiments at any excitation wavelength. This model can also account for apparently contradictory trends reported in literature, since the clustering of the sp2 phase and the sp3 to sp2 conversion are separately treated.
Electrical Property of Vertically Grown Carbon Nanotube and its Application to the Nanofunctional Devices
Authors: Chu Jaeuk , Jeong Kwangseok , Bae Eunju , Yoo Inkyeong , Choi Wonbong , Kim Jujin
Published: April 2011

A highly ordered porous alumina array which hole size is decreased down to 20nm was fabricated by a two step anodization method. Carbon Nanotube was grown vertically with thermal CVD at 600∼700 °C. By using rapid thermal annealing method, low-ohmic contact was formed between multi wall nanotubes and metal electrode and its resistance shows tens to hundreds Ω. The alumina layer which is existed between nanotube and electrode acts as a barrier for conductance. The resistance of carbon nanotube shows the temperature(T-1) dependence at 4.21K < T < 19.9K and semiconducting behavior at this temperature region.
Temperature Dependence of Cluster-cluster Coalescence in Monodispersed Co Cluster Assemblies
Authors: Peng D. L. , Hihara T. , Sumiyama K.
Published: April 2011

Using a plasma-gas-condensation-type cluster beam deposition system, we deposited monodispersed Co clusters with mean diameter d = 8.5 nm on quartz and microgrid substrates. The cluster-cluster coalescence process of the Co cluster assemblies was investigated by in situ electrical conductivity measurements and ex situ transmission electron microscopy (TEM). The change of magnetic properties induced by the inter-cluster coalescence was also discussed. The electrical conductivity measurement indicated that, at temperatures T < 100°C, the Co clusters in the assemblies maintain their original size as deposited at room temperature, while the inter-cluster coalescence takes place at T > 100°C. The TEM observation showed that the size distribution and the interface morphology of the clusters do not change markedly at substrate temperatures Ts ≤ 200°C, while cluster-cluster coalescence starts at Ts > 200°C. Above Ts = 300°C, the interfacial area of coalesced clusters is crystalline, having its own orientation different from those of two connected cluster cores.
Synthesis and Sintering Characteristics of TiC – Ni – Ti – (Al) Nanocomposites
Authors: Vohwinkel Kai , Koc Rasit
Published: April 2011

The sintering behavior of submicron / nanosize TiC powders was investigated. The TiC powders (31 wt.% carbon) are synthesized from a carbon coated precursor and have excess carbon content. Ti, Ni and Al powders were added to have in-situ intermetallic binders for sintering. The composition TiC-5 wt.% Ti (pellet 1) shows pure TiC in the XRD analysis after sintering. The composition TiC-30 wt.% Ni3Al (pellet 3) shows the formation of the liquid phase Ni3Al. No liquid phase can be clearly identified in the XRD pattern of pellet 2 (TiC-30 wt.% Ni3Ti). However the SEM micrograph of pellet 2 shows similarity to the SEM image of pellet 3 concerning the formation of liquid phase.

Pellets 1 and 2 show densifications of 100 % TD (theoretical density), whereas pellet 3 is only 90 % TD. Pellet 3 has the highest hardness (2511 HV) and fracture toughness (12.08 MPa m1/2).
Peculiarity of Properties and Some Applications of Ultra Dispersed (Nano-) Materials
Authors: Petrunin Vadim F.
Published: April 2011

Three arguments are considered as main for peculiarity of nano-sized materials properties. An unusual and unique combination of properties can be feasible in ultra dispersed (nano-) materials, for examples, high hardness and superplasticity. Some examples of ultra dispersed materials applications working out by Atomic Energy Industry program are following.
Diffusion and Ionic Conduction in Nanocrystalline Ceramics
Authors: Heitjans Paul , Indris Sylvio
Published: April 2011

Diffusion and ionic conduction in nanocrystalline ceramics, both monophase and composite, was studied by NMR relaxation and NMR lineshape as well as impedance spectroscopy. Measurements were mainly done on Li ion conductors prepared by high-energy ball milling. It was possible to discriminate between mobile ions in the interfacial regions and immobile ions in the grains. In general the diffusivity and conductivity are enhanced in the nanocrystalline monophase system as compared to the microcrystalline one, e. g. by about four orders of magnitude in the case of CaF2. An exception is, e. g., Li2O where the nano- and microcrystalline forms have similar conductivities. However, when the nanocrystalline insulator B2O3 is added to nanocrystalline Li2O the conductivity of the composite increases whereas it decreases in the corresponding microcrystalline system.
Nanocrystalline Zirconia Ceramics and Films Prepared by Chemical Vapor Synthesis and Deposition
Authors: Seydel Johannes , Winterer Markus , Hahn Horst
Published: April 2011

We have prepared thin yttria-stabilized zirconia (YSZ) electrolyte layers by chemical vapor deposition (CVD) on a pre-sintered NiO/YSZ fuel cell anode substrate. Structural analysis by scanning electron microscopy (SEM) and x-ray-diffraction shows a homogeneous, nanocrystalline layer.

Conventional electrolyte films reach desired electrical properties only at elevated temperatures, typically 1000°C to 1100°C. The YSZ films grown by CVD on rough anode substrates show better growth behavior and less defects at the anode/electrolyte interface than films deposited by conventional methods (screen printing, sol-gel). Results of electrical properties at lower SOFC working temperatures are obtained by impedance spectroscopy on pressed nanocrystalline YSZ powder pellets produced by chemical vapor synthesis (CVS).
Structure and Giant Magneto-Resistive Properties of Co and CoFe nano-particles in a Au matrix
Authors: Kooi B. J. , Vystavel T. , De Hosson J. Th. M.
Published: April 2011

This paper focuses on the relation between the microstructure and the Giant Magneto-Resistive (GMR) properties of Au80Co20 and Au80Co10Fe10 granular alloys. After annealing of quenched samples large differences in structure of Co and CoFe nano-particles arise: e.g. fcc Co versus bcc CoFe, spinodal decomposition of Co versus nucleation and growth of FeCo, truncated octahedrons for Co and plates for CoFe. Particularly the shape of the precipitates and the state of coherency at the interface between magnetic particle and non-magnetic matrix turned out to have important influences on the GMR behavior.
Substrate Based “Bricks-and-Mortar” Self-Assembly of Spherical Nanoparticle Aggregates
Authors: Boal Andrew K. , Ilhan Faysal , Rotello Vincent M.
Published: April 2011

Transmission Electron Microscope (TEM) sample girds were coated with recognition element functionalized polymer 2 and exposed to solutions of a Mixed Monolayer Protected Gold Cluster (MMPC) functionalized with a complimentarily recognition element. Interactions between the polymer and MMPC bound recognition elements provide a driving force for the formation of nanoparticle aggregates. Characterization of the resulting structures by TEM revealed that anisotropic growth of structures in the sub-micrometer size regime rapidly occurred. This process was shown to be the result of the specific hydrogen-bonding interactions between the two components. Casting films of polymer 2 from solutions of decreasing concentration achieved control over the process. This lead to the increased formation of regular, circular structuresand a decrease in random nanoparticle adsorption by the film. Analysis of the size of the circular structures revealed that a maximum diameter of approximately 1150 nm was achieved after 30 minutes exposure to MMPC 1 solutions. This size was independent of the concentration of polymer 2 solutions used to cast films.
Ab-initio modelling of atomic and molecular Hydrogen adsorption in graphite
Authors: Letardi Sara , Celino Massimo , Cleri Fabrizio , Rosato Vittorio , Volpe Manuela
Published: April 2011

Ab-initio electronic structure calculations have been used to evaluate the binding energy of atomic and molecular hydrogen to graphite lattice defects. Results show that graphite defects (Stone- Wales, vacancy) are preferred binding sites with respect to regular lattice sites. We find that molecular hydrogen is physisorbed between the graphite planes, but cannot diffuse across a graphitic plane.
Impact Ionization and Auger Recombination in Semiconductors: Implementation Within the Flapw Code
Authors: Picozzi S. , Continenza A. , Asahi R. , Mannstadt W. , Geller C. B. , Freeman A. J.
Published: April 2011

We present a method to calculate impact ionization and Auger recombination rates within density functional theory and a screened-exchange approach and implement it in the all- electron FLAPW method. We investigate the dependence of the overlap matrix elements as a function of the states involved along the main symmetry lines of the Brillouin zone. Our results for the final impact ionization rates along the main symmetry lines of the Brillouin zone. Our results for the final impact ionization rates along τ — X and τ —L directions for GaAs show a strong anisotropy imposed by energy and momentum conservation and related to the use of a realistic and accurate sX-LDA band structure.
Material Parameters for Analytical and Numerical Modeling of Si and Strained SiGe Heterostructure Devices
Authors: Jain S. C. , Mehra A. , Decoutere S. , Schoenmaker W. , Willander M.
Published: April 2011

We present calculated values of effective masses, bandgap reduction, and Fermi energy of p-doped Si and strained p-doped SiGe layers. The calculations have been made for Ge concentrations in the range 0 to 30% and boron concentration in the range 1018 cm−3 to 3×1020 cm−3. Empirical expressions for the effective masses are given. These expressions and calculated values of the other parameters are convenient for use in computer codes for modeling device processing and performance. To validate the calculated values, we have compared them with the available experimental results. Good agreement between the calculated and the experimental values is found.
Modeling of Chlorine Related Defects and Complexes in ZnMgSe
Authors: Yang Yaxiang , Muratov Leonid , Cooper Bernard R. , Myers Thomas H. , Wills John M.
Published: April 2011

We have used the ab-initio full potential LMTO method to model native defects and chlorine-impurity-related defects in ZnSe and ZnxMg1−xSe. Our results show that there is a strong tendency for formation of a defect complex between a chlorine impurity at the Se site and a vacancy at the neighboring Zn site. The formation energies of this complex and other chlorine related defects decrease in the presence of magnesium. However, the maximum achievable electron concentration in the presence of magnesium is lower because of the increase in the band gap.
Investigation of the Electron Energy Spectrum in a Three Dimensional Regimented Tetragonal Quantum Dot Superlattice
Authors: Lazarenkova Olga L. , Balandin Alexander A.
Published: April 2011

We analyze the electron energy spectrum in three-dimensional regimented arrays of semiconductor quantum dots. The coupling among quantum dots results in formation of three- dimensional electron mini-bands. Changing the size of quantum dots, inter-dot distance, barrier height and regimentation, one can control the electronic band structure of this quantum dot superlattice, which can also be referred to as quantum dot crystal due to its structure and energy spectrum that resemble those of a real crystal. Results of computer simulations carried out for a tetragonal InAs/GaAs quantum dot superlattice show that the electron density of states, effective mass tensor and other properties are different from those of bulk and conventional quantum well superlattices.