bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructural Studies of Sputtered Co90Fe10/Ag GMR Multilayers
Authors: Jarratt J.D. , Klemmer T.J. , Barnard J.A. 
Published: April 2011

ABSTRACTThe microstructure of Co90Feio/Ag giant magnetoresistive multilayer films has been investigated using x-ray diffraction (XRD) and cross-sectional transmission electron microscopy. Columnar grains with a (111) fiber growth texture is observed. A comparison is made between the observed layering structure and earlier multilayer schematics based on the literature and magnetic and magnetoresistive measurements as a function of layer thickness. A direct correlation is made between superlattice satellite peak signals from selected area electron diffraction patterns and XRD scans.
Perpendicular Giant Magnetoresistance of Co/Cu Multilayers with Fluctuating Co Layer Thicknesses
Authors: Chiang Wen-C. , Loloee R. , Pratt W.P. , Bass J. 
Published: April 2011

ABSTRACTJ. Mathon has predicted that introducing pseudorandom fluctuations (PRF) in the Co layer thickness could greatly enhance the Current Perpendicular to the Plane (CPP) magnetoresistance (MR) of a Co/Cu superlattice with dimensions comparable to the electron mean-free-path. We have searched for CPP-MR enhancement in sputtered Co/Cu multilayers with Cu layer thicknesses near both the first and second antiferromagnetically coupled peaks in the oscillatory region of the CPP-MR. In both cases, inserting PRF only decreased the CPP-MR.
Theoretical Study of the Magnetic Anisotropy of Ni Films on Cu(001)
Authors: Freyss M. , Lorenz R. , Dreysse H. , Hafner J. 
Published: April 2011

ABSTRACTThe anisotropy properties of Ni films on Cu(001) are quite unusual compared to other systems: The magnetization direction of Ni is in-plane for a coverage smaller than a critical thickness of 7 monolayers and out-of-plane for a coverage larger than 7 monolayers. As a first step in the study of this unusual behaviour, we report results of ab-initio calculations of the magnetic order of Ni films on a Cu(001) substrate. The magnetic moments are computed by means of the real-space Tight-Binding LMTO method allowing non-collinear magnetic moments and including spin-orbit coupling to account for magnetic anisotropy effects. As the number of Ni layers is increased, we discuss the stability of the system with a magnetization in-plane or out-of-plane.
Lattice Effects in Perovskite and Pyrochlore CMR Materials
Authors: Kwei G.H. , Argyriou D.N. , Billinge S.J.L. , Lawson A.C. , Neumeier J.J. , Ramirez A.P. , Subramanian M.A. , Thompson J.D. 
Published: April 2011

ABSTRACTColossal magnetoresistance (CMR) in doped lanthanum manganite thin films (Lai.xMx, where M is a divalent ion) has been shown to result in a factor of 106 suppression of the resistance. The driving force for the CMR transition is thought to be the double-exchange (DE) interaction. Many studies of both the crystal structure and the local structure of the Lai.xMxMnO3 (with M = Ca, Sr and Ba, as well as Pb) system have now been carried out. As expected, these systems all show a strong coupling of the lattice to the CMR transition. On the other hand, neutron diffraction data and x-ray absorption studies for the Ti2mn2O7 pyrochlore, which also exhibits CMR, shows no deviations from ideal stoichiometry, mixed valency, or Jahn-Teller distortions of the MnO6 octahedron. We present results of crystallographic and local structural studies of these two important classes of CMR materials. compare the differences in structural response, and discuss the implications of these findings to our understanding of these materials.
Tight-binding calculation of giant magnetoresistance in Co/Cu/Co spin valves with layer-dependent scattering
Authors: Tsymbal E.Yu. , Pettifor D.G. 
Published: April 2011

ABSTRACTWe have modelled the effects of bulk, outer-boundary, and interfacial disorder on conductivity and giant magnetoresistance (GMR) in Co101010/ trilayer taking into account its realistic electronic band structure. Calculations were performed using our model [E. Yu. Tsymbal and D.G. Pettifor, Phys. Rev. B 54 (1996) 15314] extended to the systems with two-dimensional periodicity and layer-dependent disorder. The model is based on the Kubo-Greenwood formula and spin-independent disorder in the on-site atomic energy levels, reflecting the scattering by defects, within an spd tight-binding approximation. Exploring the contributions to conductivity from different layers, we find that the influence on GMR of the boundary and interfacial scattering is similar to the bulk scattering, because the conductivity is non-local and the thicknesses of films are comparable to the electronic mean free path. Increasing the spin-independent disorder causes a decrease of GMR in the spin-valve for both interfacial, outer-boundary and bulk mechanisms of scattering. We have also investigated the effect of outer-boundary and interfacial paramagnetic Co layers on GMR in the trilayer. We find that the GMR, in this case, is strongly reduced due to the strong spin-independent scattering at the paramagnetic layers and hybridization of d states of the paramagnetic layers with the sp bands.
Magnetic Properties of Transition Metal Interfaces
Authors: Mirbt S. 
Published: April 2011

ABSTRACTThe results of first-principles calculations for the interlayer coupling in Fe/Cr/Fe trilayers are presented. We find that a spin-density wave in Cr gives rise to an additional contribution to the interlayer coupling. We investigate the relationship between the spacer magnetic moment and the interlayer coupling. Moreover we calculated the effect of interface adlayers of Cu on the interlayer coupling of a Fe/Cr/Fe trilayer.
Temperature Dependence of Strong Exchange Coupling in Ferrite Heterostructures
Authors: Suzuki Y. , Van Dover R.B. , Felder R.J. 
Published: April 2011

ABSTRACTSingle crystalline spinel structure ferrite thin film bilayers exhibit nearly ideal exchange coupling at room temperature. In these bilayers, the blocking temperature is only limited by the Curie temperature of the (Mn,Zn)Fe2O4. Up to the Curie temperature of the soft (Mn,Zn)Fe2O4 layer, the magnetization loops indicate that exchange anisotropy dominates the magnetization of the soft layer up to magnetic fields on the order of the coercive field of the hard CoFe2O4layer.
Bilinear and Biquadratic Exchange Coupling in Fe(110)/Cr/Fe Trilayers
Authors: Elmers H.J. , Schwabenhausen J. , Dürkop T. 
Published: April 2011

ABSTRACTThe indirect exchange coupling in W(110)/Fe/Cr/Fe/Cr trilayers was determined by analysis of magnetization curves measured by Kerr magnetometry. We adjusted the uniaxial in-plane anisotropies in the two Fe layers in such a way that the easy axes were orthogonal, [001] in the 1st, [110] in the 2nd layer. This allows an independent determination of both bilinear (i) and biquadratic (J2) coupling constants. We determined tJ and J2 as a function of Cr interlayer thickness (tcT = 0 – 4 nm), preparation temperature of the interlayer Tcr=100 – 500 K, and as a function of temperature (T = 100 – 300 K). Results for the exchange coupling are correlated to the particular lateral thickness fluctuation of the Cr spacer.
Exchange Coupling and Giant Magnetoresistance in Electrodeposited Co/Cu Multilayers
Authors: Dinia A. , Rahmouni K. , Schmerber G. , El Fanity H. , Bouanani M. , Cherkaoui F. , Berrada A. 
Published: April 2011

ABSTRACTWe present the results of the transport and magnetization measurements of electrodeposited Co/Cu multilayers grown in a single electrolyte based on C0SO4, H3BO3 and CuSO4. The samples are deposited on glass substrate covered by a 500 Å thick Cu buffer layer. X-ray diffraction performed on the samples shows fee structure of both Co and Cu layers with preferential (111) orientation. Resistivity measurements show a giant magnetoresistance effect of about 4% at room temperature for multilayers with Co and Cu thickness between 4 nm ≤ tco ≤ 6 nm and 3 nm ≤ tcu ≤4 nm respectively. For Co thickness tCo ≤ 15 nm, the magnetoresistance completely vanishes indicating that there is no more continuous Co layer. The indirect antiferromagnetic exchange coupling between magnetic Co layers is relatively large for 4 nm thick Cu spacer layer and gives rise to a temperature dependence of about 30% between room temperature and 4.2 K.
A New Spin Filter: The Magnetic Schottky Diode
Authors: Filipe A. , Drouhin H.-J. , Lampel G. , Lassailly Y. , Peretti J. , Safarov V.I. , Schuhl A. 
Published: April 2011

ABSTRACTWe observe spin-dependent transmission of hot electrons through the ferromagnetic metallic layer of a Schottky diode. A 25% spin-polarized electron beam is produced in vacuum by a GaAs photocathode under illumination with circularly polarized light. The photoemitted electrons are then injected from the vacuum into the sample: a 3.5 nm-thick Fe layer deposited on a n-doped GaAs substrate. We measure a transmission coefficient of the order of a few 10-4. Using an incident energy above the Fermi level equal to 5 eV, a 5% asymmetry in the transmitted current is observed by changing the spin-polarization of the incident electrons (i.e. the light polarization) and/or reversing the Fe-layer magnetization. This corresponds to a transmission spin-dependence of 20% for a 100% spin-polarized incident beam.
Low Dielectric Constant Fluorinated Polyimides for Interlayer Dielectric Applications
Authors: Pellerin John , Fox Robert , Ho Huei-Min 
Published: April 2011

AbstractThis paper presents the results of development, characterization and integration screening of low dielectric constant (low k) fluorinated polyimides for interlayer dielectric applications. Evolution of these materials has progressed with the intent of improving fundamental thin film properties, such as thermal stress behavior, modulus, CTE, and dielectric constant. Further refinements to fluorinated polyimides have been to improve their process compatibility and integration characteristics, primarily in the area of deep sub-micron gap filling. The avenues taken to attain these objectives will be illustrated.Subsequent integration of low k fluorinated polyimides has been achieved for a completed single-level metal BEOL test vehicle to highlight the impacts of the film's adhesion, mechanical and thermomechanical properties. In addition, the completed fluorinated polyimide single-level metal structures have been used to characterize electrical performance in contrast to single-level metal structures with TEOS dielectric. Intralevel capacitance and leakage current have been measured with dual comb and serpentine structures. Modeling has been applied to verify dielectric constant in submicron geometries from the capacitance measurements.
Characterization of Parylene-N Thin Films for Low-K Vlsi Applications
Authors: Selbrede Steven C. , Zucker Martin L. 
Published: April 2011

AbstractParylene-N thin films were characterized from the viewpoint of advanced VLSI intermetal dielectric applications. All films were deposited in a prototype production system that included a vacuum chamber, electrostatic cold chuck and a parylene vapor delivery system. Chuck temperatures as low as -30 °C were achieved. The deposition rate was found to be strongly dependent on wafer temperature, increasing dramatically as wafer temperature is reduced. Deposition rate was also strongly dependent on the parylene vapor flow rate and process pressure. These strong dependencies require that extreme care be taken to achieve production worthy repeatability.A number of film properties were measured including; dielectric constant, refractive index, stress, adhesion, conformality, OH-content, metals-content and thermal stability.
Microscopic Mechanisms for Reduced Static Dielectric Constants in Si-O-F Alloy Films
Authors: Yang H. , Lucovsky G. 
Published: April 2011

AbstractThere is considerable interest in insulators with static dielectric constants lower than SiO2; an alloy system attracting recent attention is Si-O-F. Alloying of F atoms into plasma-deposited SiO2films leads to major changes in the SiO2bond-stretching and -bending infrared bands accounting for a significant fraction of the reduction in the dielectric constant. These changes are explained by F induced modifications of force constants and effective charges of the neighboring Si-O-Si groups.
Cure of Hydrogen Silsesquioxane for Intermetal Dielectric Applications
Authors: Bremme J.N. , Liu Y. , Gruszynski K.G. , Dall F.C. 
Published: April 2011

AbstractCure is a significant process during back end of the line fabrication of integrated circuits with hydrogen silsesquioxane since it affects structure and properties of the spin on dielectric material. Reported herein is the effect of soak temperature, time, and oxygen concentration process parameters on structure and properties of hydrogen silsesquioxane. Results of the study emphasize the importance of an inert environment during the baseline recommended cure conditions of 400 °C for one hour in order to avoid oxidation and formation of polar silanol or water species. A 350 °C cure temperature is more robust to oxidation providing similar or improved properties. Shorter cure times result in similar structure and properties as the baseline cure which suggests that lower temperature and/or shorter cure time may provide value worth investigating by integrated circuit manufacturers.
Direct Patterning of Low-K Material for Damascene Process
Authors: Chu Cheng-Jye , Chu C-T. , Wei Q. 
Published: April 2011

AbstractThere are several activities in the development of low dielectric constant materials, including fluorlnation of SiO2, low-k organic polymers, and porous materials. No one material satisfies all the requirements for multilevel interconnections, which include low dielectric constant, high mechanical strength, good dimensional stability, good high temperature stability, easy processing, and low H2O absorption and outgassing. In this research, a new material system has been studied. This process-controlled low-k material can have dielectric constant as low as 2.0 with good thermal stability. It can provide low viscosity for reflow processing to achieve excellent planarization and gap filling. Low moisture uptake and high mechanical strength can be achieved. Most interesting is, it can be made to be photosensitive at deep-UV range, which provides the possibility of eliminating many chemicals and complicated processes in photolithography. Process cost can be expected to drop significantly. Damascene and dual damascene processes were proposed using this new low-k material, which can be much simpler compared to the traditional process.
Reaction between Low Dielectric Constant Fluorinated Polyimide and Aluminum
Authors: Tong H. Y. , Szalkowski F. J. , Shi F. G. , Zhao B. , Brongo M. , Wang S.-Q. , Vasudev P. K. 
Published: April 2011

AbstractInteractions between fluorinated polyimide and aluminum under different thermal treatment conditions have been investigated using transmission electron microscopy (TEM) and x-ray diffractometry (XRD) techniques over a wide temperature range. Our results suggest that the oxygen from the dielectric materials may result in the oxidation of the underlying aluminum either on the surface or along the grain boundary. This work implies that processing conditions, such as curing temperature and time, may play critical roles in affecting the performance of polymeric dielectric materials.
Silk Polymer Coating with Low Dielectric Constant and High Thermal Stability for Ulsi Interlayer Dielectric
Authors: Townsend P. H. , Martin S. J. , Godschalx J. , Romer D. R. , Smith D. W. , Castillo D. , DeVries R. , Buske G. , Rondan N. , Froelicher S. , Marshall J. , Shaffer E. O. , Im J-H. 
Published: April 2011

AbstractA novel polymer has been developed for use as a thin film dielectric in the interconnect structure of high density integrated circuits. The coating is applied to the substrate as an oligomeric solution, SiLK*, using conventional spin coating equipment and produces highly uniform films after curing at 400 °C to 450 °C. The oligomeric solution, with a viscosity of ca. 30 cPs, is readily handled on standard thin film coating equipment. Polymerization does not require a catalyst. There is no water evolved during the polymerization. The resulting polymer network is an aromatic hydrocarbon with an isotropie structure and contains no fluorine.The properties of the cured films are designed to permit integration with current ILD processes. In particular, the rate of weight-loss during isothermal exposures at 450 °C is ca. 0.7 wt.%/hour. The dielectric constant of cured SiLK has been measured at 2.65. The refractive index in both the in-plane and out-of-plane directions is 1.63. The flow characteristics of SiLK lead to broad topographic planarization and permit the filling of gaps at least as narrow as 0.1 μm. The glass transition temperature for the fully cured film is greater than 490 °C. The coefficient of thermal expansivity is 66 ppm/°C below the glass transition temperature. The stress in fully cured films on Si wafers is ca. 60 MPa at room temperature. The fracture toughness measured on thin films is 0.62 MPa m ½. Thin coatings absorb less than 0.25 wt.% water when exposed to 80% relative humidity at room temperature.
Evaluation of a New Strategy for Transverse Tem Specimen Preparation by Focused-Ion-Beam Thinning
Authors: Shaapur F. , Stark T. , Woodward T. , Graham R. J. 
Published: April 2011

AbstractIn this paper, different variations of a recently developed focused ion beam (FIB)-based TEM specimen preparation technique are studied conceptually and experimentally, compared, and evaluated. This procedure mainly consists of formation, removal, transport, and mounting of an electron transparent transverse membrane on a support grid for TEM study. Based on the experimental results obtained from this evaluation, some modifications have been conceived and implemented. These details as well as other critical information have been presented and discussed.
Focused Ion Beam Sample Preparation of Non-Semiconductor Materials
Authors: Phaneuf M. W. , Rowlands N. , Carpenter G. J. C. , Sundaram G. 
Published: April 2011

AbstractFocused Ion Beam (FIB) systems have been steadily gaining acceptance as specimen preparation tools in the semiconductor industry. This is largely due to the fact that such instruments are relatively commonplace as failure analysis tools in semiconductor houses, and are commonly used in the preparation of cross-sections for imaging under the ion beam or using an electron beam in an SEM. Additionally, the ease with which cross-sectional TEM specimens of semiconductor devices can be prepared using FIB systems has been well demonstrated. However, this technology is largely unknown outside the semiconductor industry. Relatively few references exist in the literature on the preparation of cross-sectional TEM specimens of non-semiconductor materials by FIB.
This paper discusses a specific use of FIB technology in the preparation of cross-sectional TEM specimens of non-semiconductor samples that are difficult to prepare by conventional means. One example of such materials is commercial galvannealed steel sheet that is used to form corrosion resistant auto-bodies for the automobile industry. Cross-sectional TEM specimens of this material have proved difficult and time-intensive to prepare by standard polishing and ion milling techniques due to galvanneal's inherent flaking and powdering difficulties, as well as the different sputtering rates of the various Fe-Zn intermetallic phases present in the galvannealed coatings. TEM results from cross-sectional samples of commercial galvannealed steel coatings prepared by conventional ion milling and FIB techniques are compared to assess image quality, the size of the electron-transparent thin regions that can be readily prepared and the quality of samples produced by both techniques. Specimen preparation times for both techniques are reported.
Surface Science Aspects of Contamination in Tem Sample Preparation
Authors: Grant John T. , Walck Scott D. , Scheltens Frank J. , Voevodin Andrey A. 
Published: April 2011

AbstractWith the advent of the modem analytical electron microscope with its ultrahigh vacuum conditions, extremely high current density in a very small probe, and its light element analysis capability, it is imperative that contamination of the TEM sample, particularly by hydrocarbons, is eliminated. The degree of cleanliness required for analysis using surface sensitive techniques is also much greater than for other forms of analysis. Contamination of samples can occur (a) prior to analysis, due to the way samples are prepared or handled, or (b) during analysis. Examples of surface contamination prior to analysis and during analysis will be given, in order to illustrate their effect on an analysis.Polished Si, Ni, and Ti bulk samples and pre-thinned TEM Ni and Ti samples were intentionally contaminated by two methods. One set of samples was put on a liquid nitrogen cooled stage for one hour in a diffusion pumped Gatan Duomill in which the liquid nitrogen cold trap above the diffusion pump was intentionally left warm. The other set was contaminated by dipping them into a 100 ml solution of acetone containing 0.04 g of an acetone-soluble low temperature wax. Two commercially available plasma cleaners, specifically designed for eliminating hydrocarbon contamination, were used to clean the samples. The bulk samples were examined with x-ray photoelectron spectroscopy and the TEM samples were examined in a 200 keV analytical TEM. The results from these experiments will be discussed.
Kinetic Lattice Monte Carlo Simulations of Diffusion and Decomposition Kinetics In Fe-Cu Alloys: Embedded Atom and Nearest Neighbor Potentials
Authors: Wirth B. D. , Odette G. R. 
Published: April 2011

ABSTRACTIn principle, Kinetic Lattice Monte Carlo (KLMC) methods can accurately simulate the precipitation of coherent phases by tracking the motion of a vacancy and the corresponding diffusion and clustering of solutes. The fidelity of the KLMC simulations depends primarily on the validity of the assumed interatomic potentials. These potentials must provide accurate solute-solute-solvent-vacancy energetics over the length scales relevant to the physical decomposition paths. Of course, simulating long range strain energy interactions is the biggest challenge, but the significance of this contribution is less in systems manifesting primarily dilational strains. Simple nearest neighbor (NN) potentials, used in previous KLMC of decomposition kinetics of dilute Fe-Cu alloys are generally not able to reproduce alloy property combinations like vacancy formation energies, dilute heats of solution and the coherent interface energies. Further, solute diffusion in bcc alloys requires jumps between first and second nearest neighbors, and is governed by, at minimum, at least three independent jump frequencies. The jump frequencies are controlled by the binding energies of atoms out to at least second nearest neighbor positions (which are only about 15% further away from the solute than the first nearest neighbor) and are also influenced by solute-modified saddle point activation energies. Thus longer range multiatom embedded-atom-method (EAM) type potentials can, in principle, provide a more realistic simulation of diffusion and solute clustering compared to NN based models. However, this refinement comes at a much higher computational cost. While they cannot be directly compared, this study presents KLMC results for both a simplified EAM versus a NN potential, and describes important new mechanistic insight provided by these atomistic simulations.