bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long and Short Range Oscillatory Exchange Coupling in Fe/Cu and Co/Cu Magnetic Multilayers
Authors: Herman F. , Sticht J. , Schilfgaarde M. Van 
Published: March 2011

AbstractBy carrying out accurate first-principles superlattice calculations, we determined the exchange coupling in bcc Fe/Cu and fcc Co/Cu multilayers as a function of the Cu spacer thickness. The fact that we can obtain long-range oscillatory coupling directly from first principles suggests that our theoretical model includes the underlying physical mechanism, and that such coupling is indeed a band structure effect. The exchange coupling depends on the interfacial orientation as well as on the Cu spacer thickness. In bcc [001] Fe/Cu, fcc [001] Co/Cu, and fcc [110] Co/Cu, the coupling has both long and short-range oscillatory components, while in fcc [111] Co/Cu, the long-range component dominates. Using a simplified model for the Fermi surface of the Cu spacer, we can relate the short-range oscillations to electronic transitions across the Fermi sphere, and the long-range oscillations to electronic transitions between spheres in adjacent zones in extended k-space, i.e., to interzonal transitions.
Magnetism in 4d Transition Metal–Ag(001) Sandwiches
Authors: Clougherty Dennis P. , Mchenry M. E. , Maclaren J. M. 
Published: March 2011

AbstractUsing ab-initio spin-polarized layer Korringa-Kohn-Rostoker (LKKR) band structure calculations, we investigated the possibility of having a stable ferromagnetic ground state in 4d transition metal (TM)–Ag(001) sandwiches (TM = Tc, Ru, Rh, and Pd). In contrast to recent calculations performed on systems with TM overlayers on Ag (001), we find that the TM sandwich configuration gives a paramagnetic ground state. While excellent agreement in general is obtained for the layer-projected densities of states (LDOS), the sandwich configuration lowers the densities of states at the Fermi energy (EF) in the case of Rh and Ru by a small amount which seemingly prevents the marginal ferromagnetic instability predicted by Eriksson et. al. (Phys. Rev. Lett. 66, 1350 (1991)) from occurring.
Substructure-Magnetic Property Correlation in Co/ag Composite Thin Films
Authors: Reed C.P , Deangelis R.J. , Liou S.H. , Nafis S. , Woollam John A. , Lee K.W. , Jacob R.J. 
Published: March 2011

AbstractThree series of nanostructured, μm thick, Co/Ag composite thin films (13, 39 and 61 volume % Co) were produced by dc magnetron sputtering at various substrate temperatures (100–600°C) to determine their magnetic properties and characterize the microstructure. The films were found to be composed of finely dispersed Ag and Co particles. The film surfaces become rougher as the substrate temperature was increased. The crystal lattice structure of the Co was found to be fcc except at the lower substrate temperatures (<300°C) in the 61 volume % films where it was found to be a mixture of fcc and some hcp. The average diffracting particle size of both the Co and Ag rich phases increase with substrate temperature. The magnetic coercivity of the films reached a maximum value when the Co particle size was between 100–150Å.
Small d-Spacing and Internal Stress of Co-Cr Films Deposited by Kr Ion Sputtering
Authors: Akiyama S. , Nakagawa S. , Naoe M. 
Published: March 2011

AbstractIt is important to control the internal stress of the deposited film because the magnetic tape is becoming thinner for attaining higher recording density per volume. Kr gas was used as the working gas in the facing targets sputtering (FTS) system for depositing Co-Cr films. Kr gas has the larger ionization cross section and atomic mass than those of Ar, Co and Cr, so that Kr gas could make stable discharge at lower pressure and the recoiling of Kr atoms on the surface of the Co-Cr target was more effectively suppressed. Therefore, Kr ions seem to be more advantageous as working gas than Ar ions which are the most common working gas. The FTS method with Kr ions could deposit the stress-free Co-Cr films with good crystallinity. Actually, Δθ50 and (Mr/Ms) of Co79Cr21 films deposited on Si wafer by Kr ion sputtering in the pressure range of 10–4 ∼ 5×10−−5 Torr were as small as 4% and 0.1, respectively. The colpressive stress of 1500Å-thick Co79Cr21 films was as small as 108 dyne/cm2, of which the value was smaller than 10% of that by Ar ion sputtering. Therefore, the combination of the FTS method and Kr gas seems to be very convenient for solving the problem of the internal stress.
Spin-Polarized Scanning Tunneling Microscopy (SPSTM)
Authors: Wiesendanger R. , Buergler D. , Tarrach G. , Shvets I.V. , Guentherodt H.-J. 
Published: March 2011

AbstractWe report on a novel promising technique for the investigation of magnetic structures at surfaces at high spatial resolution, ultimately down to the atomic scale. This technique is based on the observation of vacuum tunneling of spin-polarized electrons by means of a scanning tunneling microscope (STM). We discuss appropriate probe tips for the spin-polarized STM (SPSTM) and describe initial experimental results. We further focus on the information obtained by SPSTM. Finally, the perspectives of SPSTM will be discussed.
Micro- and Nanostructure of Co/Pd and Co/Au Multilayers Studied with Transmission Electron Microscopy
Authors: Hakkens F. , Coene W. , Broeder F.J.A. Den 
Published: March 2011

AbstractSeveral metallic multilayers with very thin magnetic Co layers display a preferred magnetization perpendicular to the interfaces. There are strong indications that the magnitude of this anisotropy depends critically on details of the microstructure of the multilayers, and especially on the atomic structure of the interfaces. The micro- and nanostructure of Co/Pd and Co/Au multilayers, which exhibit a large difference in lattice parameter (9% and 14% respectively), was studied by conventional transmission electron microscopy (TEM) and high resolution TEM (HREM). The multilayers, grown by vapor deposition, show a columnar structure and have a convex curvature in the growth direction. In Co/Au multilayers also the Au lattice is bent. Misfit dislocations are observed at the interfaces even for Co layers of one atomic layer thickness. Generally the interfaces show atomic roughness, which is more severe for Co/Au than for Co/Pd.
The Role of Next-Nearest Neighbors in The Neel Model of Surface Anisotropy for BCC Crystals
Authors: White Robert L. , Clemens Bruce M. 
Published: March 2011

AbstractWe have extended the Neél model of surface anisotropy in b.c.c. crystals to include next nearest neighbor interaction. Fitting the experimental data for Fe (001) and (110) surfaces leads to some pradoxes which cast doubt on the Neél surface anisotropy as the dominant source of surface anisotropy in thin films.
Magnetoelastic Interactions at Surfaces and Interfaces
Authors: O'Handley R. C. , Sun S. 
Published: March 2011

AbstractThe contribution of strains to anomalous surface and interface magnetic anisotropies cannot be analyzed quantitatively without knowledge of the ME coupling coefficients there. We have measured the ME coupling coefficients Bs near the surface (~0.5nm) of two amorphous alloys, Fe77Cr6B17 (with bulk magnetostriction λs = +7 × 10−6) and Co76Cr4B20 (λs = -3.8 × 10−6) and found them to differ significantly from the bulk values Bb: Fe-base, Bs = -1.7 × 105 J/m3 (57% of Bb) and Co-base, Bs = 5.8 × 105 J/m3 (three times Bb).
Photochenistry And Photophysics Of Materials In Zeolites.
Authors: Iu Kai-Kong , Liu Xinsfleng , Thomas J. Kerry 
Published: March 2011

ABSTRACTPyrene is used as a molecular probe to study surface polarity, constrained character of diffusion, oxygen diffusion, effects of coadsorbed water, and exchange cations in zeolites A, X and Y. The experimental methods include both steady-state and time-resolved fluorescence spectroscopy, and diffuse reflectance absorption spectroscopy. The properties of CdS and TiO2 constructed in zeolites are also presented.
PbI2 Confined In The Spaces Of LTA Zeolites
Authors: Terasaki O. , Tang Z. K. , Nozue Y. , Goto T. 
Published: March 2011

ABSTRACTPbI2 clusters confined in spaces of LTA zeolite are successfully prepared through vapour phase. An HREM image showed that the crystallinity of the zeolite was preserved after preparation and showed directly that the clusters were incorporated into the α-cages. Absorption spectra were measured by diffuse reflection method as a function of loading density of PbI2 molecules. Several absorption bands from different cluster sizes were observed and showed remarkable blue shift. At the maximum loading, extra reflections, which are forbidden for Fm3A of LTA, were observed in electron and X-ray diffraction patterns. The appearence of the extra reflections and the dependence of absorption curve on the loading density suggest that superlattice of clusters was produced. The characteristic feature of zeolites as containers to make an artificial superlattice of clusters is pointed out.
Molecular Design Of Aluminosilicate Thin Film Devices
Authors: Creasy Kenneth E. , Deng Ying Ping , Park Jongman , Borgstedt Eric V. R. , Davis Shawn P. , Suib Steven L. , Shaw Brenda R. 
Published: March 2011

ABSTRACTThin film coatings of NaY, NaA and ZSM-5 zeolites have been grown on copper and platinum substrates. Such materials have ion-exchange properties, molecular sieve pore size distribution, zeolitic surface areas and are crystalline. Size and charge selective electrodes, oxygen reduction fuel cells, and thin layer chromatography devices have been produced with these materials.
The Physicochemical Properties Of Vpi-7: A Microporous Zincosilicate With Three-Membered Rings
Authors: Annen Michael J. , Davis Mark E. , Higgins John B. , Schlenker John L. 
Published: March 2011

ABSTRACTThe synthesis of materials with void volumes in excess of 50% is an ongoing challenge in molecular sieve science. It has been shown that a correlation exists between the minimum framework density (FD) and the smallest ring in which all tetrahedral atoms reside (MINR). Based on this evidence it appears that materials containing 3-membered rings (3MR) will be necessary in order to obtain FDs lower than those currently attainable. Several framework beryllosilicate minerals including the natural zeolite, lovdarite, contain 3MRs. Unfortunately, beryllium can form highly toxic compounds that limit its suitability for many applications. Thus, in this study we have searched for a replacement for Be and have found that zinc is a suitable substitute with respect to the formation of three-membered rings.We report here VPI-7, a novel zincosilicate molecular sieve which contains three-membered rings. The VPI-7 framework contains rings composed of 3–, 4– and 5 T-atoms which form unidimensional 8– and intersecting 9MR channels.
Novel And Promising Applications Of Molecular Sieves In Organic Synthesis And Their Contribution To Environmental Protection
Authors: Hoelderich Wolfgang F. 
Published: March 2011

ABSTRACTZeolite catalyts have acquired considerable technical and economical importance in refinery technology and petrochemistry. Over the past ten years, the search for applications of zeolite catalysis in the synthesis of organic intermediates and fine chemicals has been stepped up. An important aspect in this development is the changeover of reactions carried out over homogeneous catalysts to heterogeneous zeolite catalysis.From this range of applications, it is intended to present two selected processes. These are the synthesis of pivalic acid and -caprolactam. The dependence on test parameters and on the catalyst properties such as acidity and doping, is described. A comparison is made with the conventional process carried out industrially. The advantages and disadvantages of the zeolite-catalyzed process are weighed up against one another.The production of ε-caprolactam and pivalic acid by heterogeneous catalysis over zeolite catalysts offers a genuine alternative to the industrial processes employing homogeneous catalysis, particularly from the point of view of environmental protection, since the use of toxic BF3and NH2OH as well as the inevitable coproduction of ammonia sulfate is avoided.
An Investigation of Buried Layer Formation by 40keV Oxygen Implantation Into Silicon
Authors: Li Y. , Kilner J. A. , Chater R. J. , Tate T. J. , Hemment P. L. F. , Nejim A. 
Published: March 2011

ABSTRACTDevice grade single crystal <100> silicon wafers have been implanted with 40keV oxygen ions over a dose range of 2×1017 to 8×1017/cm2 at a temperature of 5507±10°C. The specimens have been analyzed, both before and after high-temperature annealing at 1320°C for six hours, using SIMS, RBS, and TEM. During implantation a continuous buried SiO2 layer forms when the dose after which the buried SiO2 layer grows primarily toward the surface. After annealing samples implanted with the doses of both 2×1017 and 3×1017/cm2 it was observed that a defective SIMOX like structure was formed. Implanting with a dose of 4×1017/cm2 results in pit formation in the silicon overlayer. For the sample implanted with a higher dose of 5×1017/cm2, a non-continuous poly-crystalline silicon “overlayer” was formed. It would thus appear that when a single step implantation route is chosen, there is a dose (or layer thickness) limit for the production of a thin film SIMOX structure.
Effect of Intermediate Thermal Processing on Microstructural Changes of Oxygen Implanted Silicon-on-Insulator Material
Authors: Lee J. D. , Park J. C. , Krause S. J. , Roitman P. , El-Ghor M. K. 
Published: March 2011

ABSTRACTThe microstructural changes in oxygen implanted silicon-on-insulator material (SIMOX) at intermediate annealing steps and the changes by rapid thermal annealing (RTA) were studied with transmission electron microscopy. Defects found in as-implanted SIMOX, including multiply faulted defects, short stacking faults, and {113} defects, were all removed in anneals from 900°C to 1100°C. The threading dislocations in annealed material form at these temperatures during thermal ramping. RTA shows that the microstructure is significantly influenced by the ramp rate. The very high ramp rate in RTA results in very flat interfaces and a buried oxide layer with no Si islands, but significantly increases the defect density. Overall, the results show that intermediate thermal processing steps strongly affect the final microstructure of SIMOX material.
Avoiding Dislocation Formation for B, P, and As Implants in Silicon
Authors: Liefting J. R. , Raineri V. , Schreutelkamp R. J. , Custer J. S. , Saris F. W. 
Published: March 2011

ABSTRACTImplants of B, P, and As in Si lead to dislocation formation after 900°c annealing if a critical amount of implant damage is exceeded. However, it is possible to implant higher doses without forming dislocations if the dose is implanted in several sub-critical steps. Annealing between each step removes the (sub-critical) implant damage and dislocations do not form. Such avoidance of dislocation formation is demonstrated for 80 keV implants of B and MeV implants of B, P, and As.
C Implantation for Suppression of Dislocation Formation
Authors: Liefting J. R. , Custer J. S. , Saris F. W. 
Published: March 2011

ABSTRACTThis paper will show that annealing of Si implanted with moderate doses of 725 keV B results in the formation of secondary defects, the so-called category I dislocations. Surprisingly, 12C, with roughly the same mass as 11B, behaves in a very different way. Carbon implant damage does not result in dislocation formation even for damage levels > 100 times higher than that required for B implants. C is also able to avoid dislocation formation of co-implanted B ions. The C-dose needed to avoid dislocation formation for the B implant increases nonlinearly with B-dose. Special C-related secondary defects remain after annealing if the C-dose is higher than 4×1015 /cm2.
X-Ray Diffraction Analysis of Damage and Doping Effects in Low-Dose, High-Energy Implanted Silicon
Authors: Klappe Jos G.E. , Bársony István , Ryan Tom W. 
Published: March 2011

ABSTRACTHigh-Resolution X-Ray Diffraction is investigated as a technique for analysis of low-dose, high-energy implanted (001) silicon. The choice of the proper Bragg reflection for the rocking curve measurements is showed to be of crucial importance. The (026)1 reflection appears to be the most suitable for strain caused by implantation damage. By a qualitative analysis of rocking curves taken on B and P implanted Si samples, it could be established that the minimum dose, for which HR-XRD is sensitive enough, is about 1.5.1014cm−2 and 5.1013cm−2 for P and B, respectively. The necessary minimum peak temperature that was determined for a complete damage anneal with the T-RTA of P implanted Si with energies ranging from 0.5 to 1.5 MeV, was 1400 K for all doses of P considered. For B the required optimum peak temperature is about 1375 K.
Dependence of Profiles of Arsenic Implanted into Silicon on Tilt and Rotation Angles
Authors: Yang S. , Park C. , Klein K. , Gupta P. , Tasch A. , Simonton R. , Lux G. , McGee C. 
Published: March 2011

ABSTRACTWe have performed a comprehensive experimental study of profiles of arsenic implanted into (100) silicon for a wide range of energies, doses, tilt angles, and rotation angles. Critical angles for channeling of arsenic ions in single-crystal silicon have been calculated and are found to agree well with experimental results. The <100> axial channels and the {110} planar channels are found to be primary sources of channeling. The optimal tilt and rotation angles which minimize channeling and maximize uniformity across a wafer are deduced.
Thermal Annealing of Shallow Implanted Phosphorus in Si(100)
Authors: Yu Ning , Ma K. B. , Zhang Z. H. , Chu W. K. , Kirschbaum C. , Varahramyan K. 
Published: March 2011

ABSTRACTThe effect of channeling on the diffusion of ion implanted phosphorus in silicon has been investigated. Silicon samples, implanted with 25–100 keV P along the [100] channeling and the random equivalent directions, were subjected to thermal annealing over a temperature range of 600–1050 °C. Secondary Ion Mass Spectrometry (SIMS) and Spreading Resistance Probe (SRP) have been used to determine the atomic and carrier concentration depth profiles, respectively. The findings show that after annealing, the P profiles by implantation along the random equivalent direction can be kept shallower than the profiles obtained by implantation along the [100] channeling direction. Through proper annealing and electrical activation, only minimal diffusion in the tail region of the profiles occurred. For 50 keV P at 1×1015 at./cm2, changing the implantation from the [100] to the random equivalent direction leads to a reduction in the profile depth of about 50% (at 1×1017at./cm3). After 10 seconds of rapid thermal annealing (RTA) at 1050 °C, the profile depth remains more than 30% shallower than the channeled profile.
A New Computationally-Efficient Two-Dimensional Model for Boron Implantation Into Single-Crystal Silicon
Authors: Klein K. M. , Park C. , Yang S. , Morris S. , Do V. , Tasch A. F. 
Published: March 2011

ABSTRACTWe have developed a new computationally-efficient two-dimensional model for boron implantation into single-crystal silicon. This new model is based on the dual Pearson semi-empirical implant depth profile model [1] and the UT-MARLOWE Monte Carlo boron ion implantation model [2]. This new model can predict with very high computatational efficiency two-dimensional as-implanted boron profiles as a function of energy, dose, tilt angle, rotation angle, masking edge orientation, and masking edge thickness.
Energetic Electron Beam Induced Recrystallization of Ion Implantation Damage in Semiconductors
Authors: Bench M. W. , Robertson I. M. , Kirk M. A. 
Published: March 2011

ABSTRACTIsolated amorphous zones produced in GaAs, GaP, Si, and Ge by the implantation of 50 keV Kr+ or Xe+ ions have been induced to recrystallize under the influence of the electron beam in the transmission electron microscope. This effect has been investigated as a function of electron irradiation temperature and beam energy in the TEM. Temperature effects were investigated through irradiations performed at 30 and 300 K. The electron energies used ranged from 50–300 keV in the 300 K experiments and 200 keV electrons were used at 30 K.Recovery was induced in all of the materials even at electron energies below the threshold displacement energy indicating production of point defects within the crystalline material is not required to induce regrowth. In GaAs and GaP, recovery occurred for all electron energies studied, down to 50 keV. In Si, the beam induced regrowth rate approaches zero at an energy of 80 keV with the recovery rate increasing with increasing electron energy. At 30 K, the 200 keV electron beam induced recrystallization in all cases studied (GaAs, GaP, and Si).
Radiation-Enhanced Plastic Flow of Covalent Materials During Ion Irradiation
Authors: Volkert C. A. , Polman A. 
Published: March 2011

ABSTRACTPlastic deformation of several covalently-bound materials has been studied during ion irradiation. In all of these materials, namely crystalline and amorphous silicon, crystalline and amorphous Si0.9Ge0.1, and amorphous SiO2, the damage created by the ion beam causes density changes in the irradiated region which eventually saturate with ion dose. In the crystalline materials, the density changes were accompanied by a transformation to the amorphous phase. Superimposed on the density changes is plastic deformation which occurs during irradiation of both crystalline and amorphous materials to relieve stresses in the irradiated region. A wafer curvature measurement technique has been developed which allows the contributions from density changes and plastic deformation to be distinguished and the stress dependence of the plastic deformation to be determined.In all of the amorphous materials, the plastic deformation is Newtonian viscous shear flow, which is characteristic of solids where deformation is governed by the diffusive motion of point defects. The radiation-enhanced shear viscosity per ion was flux-independent, revealing that flow occurs rapidly, probably within the localized damaged regions created by each ion. This viscosity does not depend strongly on the material. In fact, similar viscosities were obtained during measurements of radiation-enhanced plastic deformation of crystalline covalent samples and polycrystalline aluminum films.
Distribution and Characterization of Iron in Implanted Silicon Carbide
Authors: Bentley J. , Romana L. J. , Horton L. L. , McHargue C. J. 
Published: March 2011

ABSTRACTAnalytical electron microscopy (AEM) and Rutherford backscattering spectroscopy-ion channeling (RBS-C) have been used to characterize single crystal α-silicon carbide implanted at room temperature with 160 keV 57Fe ions to fluences of 1, 3, and 6×1016 ions/cm2. Best correlations among AEM, RBS, and TRIM calculations were obtained assuming a density of the amorphized implanted regions equal to that of crystalline SiC. No iron-rich precipitates or clusters were detected by AEM. Inspection of the electron energy loss fine structure for iron in the implanted specimens suggests that the iron is not metallically-bonded, supporting conclusions from earlier conversion electron Mössbauer spectroscopy (CEMS) studies. In-situ annealing surprisingly resulted in crystallization at 600°C with some redistribution of the implanted iron.