bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unusual Behavior in The Magnetic Anisotropy of Ultra-Thin Co Sandwiches: The Role of Au Underlayers.
Authors: Marlière Christian , Engel Brad N. , Falco Charles M. 
Published: April 2011

ABSTRACTWe have used in situ polar Kerr effect measurements to study the magnetic anisotropy of X/Co/Y sandwich structures grown by MBE on Cu(111) buffers, where X and Y are variable thicknesses of Au. For fixed values of Y and in the case of an underlayer wedge, e.g. variable X value, we have found a sharp minimum in both coercive field and perpendicular anisotropy at ≈1 atomic layer of the Au underlayer. This anisotropy behavior is opposite to that of an Au overlayer deposited on a Co film, i.e. variable Y and fixed X.
Magnetic Properties of Gadolinium Silicide Thin Films for Different Heat Treatments
Authors: Pescher C. , Pierre J. , Ermolieff A. , Vannuffel C. 
Published: April 2011

ABSTRACTThe magnetic properties of heavy rare earth silicide GdSi2-x thin films are investigated as a function of the annealing temperature of the films. Resistivity measurements reveal in the two films annealed at high and low temperatures, but for a short time, the existence of two transition temperatures corresponding to the presence of an ordered and a disordered structure. In the film annealed at high temperature for a long time, only one transition temperature occurs. It corresponds to a magnetic structure transformation.
Giant Magnetoresistance and Electronic Structure
Authors: Schep Kees M. , Kelly Paul J. , Bauer Gerrit E.W. 
Published: April 2011

ABSTRACTThe electronic structure of magnetic multilayers is expected to play an important role in determining their transport properties. We explain how the conductance through a ballistic point contact is related to simple geometrical projections of the Fermi surface. The essential physics is first discussed for simple model systems and then realistic results for magnetic metallic multilayers based on first principles band structure calculations are presented. The electronic structure is shown to make an important contribution to the perpendicular giant magnetoresistance.
Growth of Fe/ZnSe Multilayers on GaAs (001) AND (111) by Molecular Beam Epitaxy
Authors: Abad H. , Jonker B. T. , Cotell C. M. , Qadri S. B. , Krebs J. J. 
Published: April 2011

ABSTRACTThe growth of Fe/ZnSe/Fe multilayers on (001) and (111) GaAs substrates is reported. The samples were characterized in-situ by reflection high energy electron diffraction (RHEED), and ex situ by vibrating sample magnetometry (VSM), ferromagnetic resonance (FMR), cross sectional transmission electron microscopy (TEM), and x-ray diffraction. On the (001) surface, the quality of the layers deteriorated significantly with the growth of the first ZnSe spacer layer. In Fe/ZnSe/Fe trilayer structures, TEM revealed a well-defined layered structure, with a high density of defects in both the ZnSe spacer layer and the subsequent Fe layer. VSM and FMR clearly showed the presence of two Fe films with distinct coercive fields, with the higher coercive field attributed to the lower crystalline quality of the second Fe layer. θ-2θ xray diffraction measurements performed on samples grown on (001) GaAs substrates indicated that the ZnSe spacer layer (grown on (001) Fe) grew in a (111) orientation. Growth on GaAs(111) substrates produced better RHEED patterns for all layers with little deterioration in film quality with continued layer growth, so that the magnetic properties of the individual Fe layer could not be distinguished.
Interface Quality and Magnetic Properties of τ MnAl/Co Superlattices On GaAs
Authors: Bruynseraede C. , Boeck J. De , Van Roy W. , Lauhoff G. , Bender H. , Van Esch A. , Mertens R. , Bland J.A.C. , Borghs G. 
Published: April 2011

ABSTRACTτ MnAl / Co superlattices are grown epitaxially on GaAs (100) substrates by molecular beam epitaxy. High angle XRD spectra are analysed and indicate that good structural quality is achieved. The behaviour of the superlattice upon annealing is described and compared with inplane and out of plane magnetization data. Extraordinary hall effect measurements show low field switching comparable to MnAl thin films. Arguments on how structural properties are affecting the magnetic properties are discussed.
The Morphology of Polytetrafluoroethylene (PTFE) Thin Films Formed by Pulsed-Laser Deposition
Authors: Norton M. Grant , Jiang Wenbiao , Dickinson J. Thomas 
Published: April 2011

ABSTRACTThin films of polytetrafluoroethylene have been formed by the pulsed-laser deposition technique. The structure of the films was found to be dependent upon the substrate temperature during deposition. At substrate temperatures from room temperature to 200°C the films were determined, by transmission electron microscopy and X-ray diffraction techniques, to be amorphous. Films formed at higher substrate temperatures were found to contain both amorphous and crystalline components. The data for the crystalline component is consistent with it being highly ordered with the long helical molecular chains aligned parallel to the film-substrate interface plane. The maximum amount of crystalline material occurred when the substrate temperature was close to the melting temperature of the polymer.
Metal Deposition on Laser Modified Teflon Surfaces
Authors: Lätsch Stefan , Hiraoka Hiroyuki , Bargon Joachim 
Published: April 2011

ABSTRACTCu, Ni, and Au were deposited with defined patterns and good adhesion by electroless plating, e-beam evaporation, and sputtering onto Teflon (polytetrafluoroethylene, PTFE), Teflon ET (PTFE-co-ethylene), Teflon FEP (PTFE-co-hexafluoropropylene) and Teflon PFA (PTFE-coperfluoroalkoxy vinyl ether) surfaces. The polymers had been irradiated in a tetramethyl – ammonium hydoxide solution (TMAH) by a Nd:YAG laser at 266 rim and by an excimer laser at 248 nrm prior to the metal deposition process. Both, the treated and virgin polymer surfaces were characterized by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and Micro-Raman spectroscopy. The increased metal to polymer adhesion at the interface was found to be due to chemical changes and is in the order Ni > Cu ≅ Au.
Photopolymerization Dynamics Studies of Acrolein on Al, Ni, and Au Substrates Using Surface Second Harmonic Generation
Authors: Chen Fang , Subrahmanyan Suchitra , Lackritz Hilary S. 
Published: April 2011

ABSTRACTThe dynamics of the gas phase photopolymerization of acrolein on aluminum (Al), nickel (Ni), and gold (Au) substrates were studied in-situ and in real time using surface second harmonic generation (SSHG) and monitoring vapor pressure decay. The Al and Ni substrates had a significant effect on the apparent rate of polymerization. A dark reaction after irradiation occurred in the absence of metal (Al or Ni) substrates, but no dark reaction was observed when the metal substrates were present. The significant differences in the metal/monomer interactions during photopolymerization are indicated by SEMs of the polyacrolein, as well as evidence from FTIR-ATR spectra. The SSHG intensities from the Au, Al, and polyacrolein surfaces were obtained.
Integrating Cell Transplantation and Controlled Drug Delivery Technologies to Engineer Liver Tissue
Authors: Mooney D. J. , Sano K. , Kaufmann P. M. , McNamara K. , Vacanti J. P. , Langer R. 
Published: April 2011

ABSTRACTEngineering liver tissue using hepatocyte transplantation may provide a new approach for treating a variety of liver diseases. However, techniques to transplant hepatocytes and promote their survival must be developed. We have developed systems to transplant hepatocytes on highly porous (95%), biodegradable sponges, and to regulate the survival of cultured hepatocytes by releasing specific growth factors in the cellular environment. Sponges were fabricated from poly (L, lactic acid) (PLLA) and polyvinyl alcohol using a particulate leaching technique. Epidermal growth factor and insulin, critical factors for hepatocyte growth and survival in culture, were incorporated into microspheres fabricated from poly (lactic-co-glycolic acid) (PLGA) utilizing a double emulsion technique. The incorporated factors were released in a controlled manner over one month in vitro, and the released factors maintained their biological activity, as measured by their ability to promote hepatocyte growth and survival in culture. The growth factor-containing microspheres could be transplanted with hepatocytes using the porous sponges, and the localized, sustained release of these factors improved hepatocyte engraftment 2-fold. These studies suggest that hepatocytecontaining tissues can be engineered using cell transplantation, and that regulating the microenvironment of transplanted cells can control their engraftment.
Rie Passivation Layer Removal by Remote H-Plasma and H2/SiH4 Plasma Processing
Authors: Ying Hong , Barnak J. P. , Chen Y. L. , Nemanich R. J. 
Published: April 2011

ABSTRACTRemote H-plasma and H2/SiH4 plasma processes were studied as potential dry cleaning processes following reactive ion etching (RIE). The processes were compared to a process of UV/ozone followed by an HF dip. The native oxide from Si(100) substrates was removed with an RIE etch of CHF3/Ar. The RIE process produced ∼150Å of a continuous fluorocarbon (CFx) passivation layer on the Si surface. For the post-RIE-cleaning three approaches were studied and compared including (1) uv-ozone exposure followed by an HF dip, (2) remote H-plasma exposure, and (3) remote H2/SiH4 plasma exposure. Auger electron spectroscopy (AES) was used to investigate the surface chemical composition, and AFM was used to measure changes in surface roughness. All three processes showed substantial removal of the passivation layer. The CF× polymer was completely removed in less than 1 min for samples exposed to a 100W remote H-plasma at 15mTorr and 450°C. With the addition of ∼0.1% of SiH4, the remote H2/SiH4 plasma also showed increased removal of residual oxygen contamination. The surface roughness of the plasma processed surfaces increased slightly.
Device Quality of Hydrogen Plasma Cleaning for Silicon Molecular Beam Epitaxy
Authors: Hansch W. , Eisele I. , Kibbel H. , KÖnig U. 
Published: April 2011

ABSTRACTDifferent substrate cleaning procedures were used before fabrication of pin diodes by silicon molecular beam epitaxy (MBE). We investigated the quality of these diodes in order to demonstrate the superior quality of a low energy plasma cleaning in an ultra-high vacuum ( UHV). This plasma cleaning by hydrogen makes a wet-chemical cleaning or a high-temperature desorption step unnecessary. Moreover, the plasma-cleaned substrates are so strongly hydrogen passivated, that they can be transported through air and processed in another MBE chamber without any additional cleaning steps.
Determination of Rinsing Parameters using a Wafer Gap Conductivity Cell in Wet Cleaning Tools
Authors: Lindquist P. G. , Walters R. N. , Throngard J. O. , Rosato J. J. 
Published: April 2011

ABSTRACTA wafer gap conductivity cell determined which rinsing parameters control the removal of wafer cleaning and etching solutions. The first part of this study focused on set up and calibration of the conductivity cell. Sodium chloride solutions with known ionic conductivities are used as model fluids. Wafer rinsing experiments showing the concentration as a function of time are analyzed. The sensitivity of the wafer gap conductivity cell is compared to a wall mounted probe, the typical method used to measure rinsing efficiency. The conductivity results are explained using a fluid dynamics model of the wafer gap.The second part of this study focused on using the wafer gap conductivity cell to study the removal of chemicals typically used in wafer cleaning processes. Experimental results show the effect of tank geometry and flow parameters on the time required for rinsing. Analysis shows the rinse process can be modeled by assuming convective fluid flow and ideal mixing. These results provide critical insight into the most important wafer rinsing parameters.
A New Low Temperature Thin Film Deposition Process: Energetic Cluster Impact (ECI)
Authors: Haberland H. , Leber M. , Moseler M. , Qiang Y. , Rattunde O. , Reiners T. , Thurner Y. 
Published: April 2011

AbstractA beam of metal cluster ions of variable size is deposited with variable kinetic energy on a substrate. Mirror-like and strongly adhering films are produced on unheated substrates for sufficiently high cluster impact energies. Numerical simulations provide the physical insight why this novel technique gives different, and sometimes superior results compared to conventional methods. Several examples are presented.
Anion Exchange Reactions and initial Gan Epitaxial Layer Formation Under Nitrogen Plasma Exposure of a GaAs Surface
Authors: Hauenstein R. J. , Collins D. A. , O‘steen M. L. , Bandic Z. Z. , Mcgill T. C. 
Published: April 2011

AbstractInitial nitridation of molecular beam epitaxially (MBE) grown GaAs surfaces by means of an electron cyclotron resonance (ECR) microwave plasma source is investigated in situ through time-resolved reflection high energy electron diffraction (RHEED), and ex situ high-resolution X-ray diffraction (HRXRD) techniques. Brief (< 8-10 s) plasma exposure of GaAs (100) surfaces results in surface N-for-As anion exchange and a new, specular, commensurate (3x3) RHEED pattern which appears to correspond to up to 1 monolayer of coherently strained GaN on GaAs. anion exchange kinetics is studied through the time-dependence of the onset and decay of the (3x3) RHEED pattern as a function of substrate temperature. For the first time, coherently strained GaNyAs1_y /GaAs heterostructures are grown and characterized. Direct evidence for thermally activated processes from both RHEED and HRXRD observations is presented, and N desorption and surface-segregation phenomena are proposed to explain the experimental results.
P-Type II-VI Compound Semiconductor Thin Films Grown by Pulsed Laser Deposition
Authors: Shen W. P. , Kwok H. S. 
Published: April 2011

AbstractIn this paper the results on p-type ZnS, ZnSe, CdS and CdSe thin films grown by pulsed laser deposition will be discussed. these films were deposited on GaAs substrates. Li-doping has been shown to be effective in producing p-type II-VI thin films, while in-doping is excellent for n-type CdS and CdSe thin films. No post-annealing process was used. these preliminary results suggest a possible new approach through pulsed laser deposition to solve the doping problem of II-VI compound semiconductors.
Siloxane Polymers as Low Dielectric Materials for Microelectronics
Authors: Wong C. P. 
Published: April 2011

ABSTRACTA modem VLSI device is a complicated three-dimensional structure that consists of multilayer metallization conductor lines which are separated with interlayer-dielectrics as insulation. This VLSI technology drives the IC device into sub-micron feature size that operates at ultra-fast speed (in excess of > 100 MHz). Passivation and interlayer dielectric materials are critical to the device performance due to the conductor signal propagation delay of the high dielectric constant of the material. Low dielectric constant materials are the preferred choice of materials for this reasons. These materials, such as Teflon® and siloxanes (silicones), are desirable because of their low dielectric constant (∈1) = 2.0, 2.7, respectively. This paper describes the use of a low dielectric constant siloxane polymer (silicone) as IC devices passivation layer material, its chemistry, material processes and reliability testing.
High Concentration Erbium Implantation of Epitaxially Grown Caf2 /Si Structures.
Authors: Raoux S. , Barriere A. S. , Lozykowski H. J. , Brown I. G. 
Published: April 2011

AbstractCalcium fluoride thin films grown on silicon substrates by sublimation under ultra high vacuum are well known to be highly efficient hosts for rare earth luminescence properties. For this reason we incorporate erbium by ion implantation in order to form optoelectronic integrated devices. Here we describe the incorporation conditions of erbium in CaF2/Si structures and their luminescence characteristics. The properties of the material have been investigated for implantation doses varying from 4×1014 to 1×1017 at.cm−2. The role of oxygen in the charge compensation mechanisms is investigated and it is shown that the maximum emission in erbium at 1.53μm occurs for an implanted dose of 2×1016 at.cm−2. This corresponds to an Er concentration three orders of magnitude greater than for the case of classical-erbium-doped semiconductors. At this high concentration (up to 15 at.%) the light emission mechanisms are of great theoretical interest. They involve strong Er-Er coupling effects: energy transfer, cross-relaxation phenomena and high conversion efficiencies.These properties make erbium-implanted CaF2/Si structures excellent candidates for the production of optically active waveguides. The guiding structure can be formed by high energy implantation to build a buried active region of high refractive index within the CaF2 thin film.
A Molecular Architectural Approach to Second-Order Nonlinear Optical Materials
Authors: Yang Xiaoguang , McBranch Duncan , Swanson Basil , Li Dequan 
Published: April 2011

AbstractThe design and synthesis of a family of calix[4]arene-based nonlinear optical (NLO) chromophores are discussed. The calixarene chromophores are macrocyclic compounds consisting of four simple D-π-A units bridged by methylene groups. These molecules were synthesized such that four D-π-A units of the calix[4]arene were aligned along the same direction with the calixarene in a cone conformation. These nonlinear optical super-chromophores were subsequently fabricated into covalently bound self-assembled monolayers on the surfaces of fused silica and silicon. Spectroscopic second harmonic generation (SHG) measurements were carried out to determine the absolute value of the dominant element of the second-order nonlinear susceptibility, d33, and the average molecular alignment, ψ. We find a value of d33 = 60 pm/V at a fundamental wavelength of 890 nm, and ψ˜ 36° with respect to the surface normal.
Optical Properties of Sol-Gel (Pb,La)TiO3 Thin Films For Waveguide Application
Authors: Bae Byeong-Soo , Lee Won-Jong , No Kwang-Soo , Yoon Dae-Sung , Kim Sung-Uk 
Published: April 2011

AbstractLead lanthanum titanate ((Pb1−x/100Lax)Ti1−x/400O3, x=10, 20, 28) sol-gel thin films were prepared on SiO2/Si and glass substrates using lanthanum nitrate as a La precursor. The effect of the processing conditions was investigated and the optical properties of the films were measured to obtain good films for waveguide applications. The perovskite crystalline phase is achieved regardless of the heating condition but the slower heating creates better quality films. La content in the film does not effect on the refractive index and transparency of the film.
Molecule-Based Approaches to High-Performance Second-Order Polymeric Nonlinear Optical Materials. Properties of Ultra-high-Tg Chromophoric Polyimides and Polyureas.
Authors: Wang Jia-Fu , Geng Lifeng , Lin Weiping , Marks Tobin J. , Wong George K. 
Published: April 2011

AbstractThis contribution describes the synthesis and properties of three classes of model NLO chromophore-functionalized high-Tg polymers which test current ideas about architecture-Tg- χ(2) performance relationships. Condensation of bismaleimides with diallylamino-functionalized donor-acceptor chromophores yields polable matrices with Tg values as high as 325°C and χ(2) responses as high as 0.7 × 10-7 esu (27 pm/V; λohigh as 0.7 × 10-7 esu (27 pm/V; λo = 1064 nm; 1.17 eV). Likewise, = 1064 nm; 1.17 eV). Likewise, condensation of o,o'-diallylbisphenol A with bismaleimides followed by chromophore functionalization yields an analogous series of polyimides with Tg values as high as 260°C and χ(2) response as high as 1.0 × 10-7 esu (42 pm/V at λo = 1064 nm). Polymerization of a bis(4-aminophenyl)lophine chromophore with bismaleimides or diisocyanates yields polymers with Tg values as high as 350°C and χ(2) = 0.62 × 10-7 esu (25 pm/V at λo = 1064 nm). All members of the above series exhibit minor to negligible decay in χ(2) response on aging in air at 100°C for 1000 h. The lophine-based material exhibits only ∼10% χ(2) decay on aging for 100 h at 200 °C under N2.
Irradiation-Induced Changes in Hydroxypropyl Cellulose
Authors: Petrich Mark A. , Rosen Lawrence A. 
Published: April 2011

AbstractGamma irradiation is used to sterilize products intended for ophthalmic and parenteral use. Ideally, the sterilization process should not affect the chemical identity or physical properties of the product. We have investigated the effects of gamma irradiation on the structure and molecular weight of hydroxypropyl cellulose (HPC), and the subsequent effect on dissolution behavior of HPC. Hydroxypropyl cellulose is a commonly used excipient in pharmaceutical formulations and tablet coatings, and can be used to manufacture water soluble objects. We find that the moisture content of the HPC influences the extent to which scission and cross-linking reactions occur. At low moisture levels (<5 wt.%), cross-linking is relatively unimportant, while above 12 wt. % moisture cross-linking becomes extensive leading to formation of insoluble, rubber-like gels.
Production of Heart Valves from Glassy Polymeric Carbon
Authors: Jenkins G. M. , Ila D. , Maleki H. 
Published: April 2011

AbstractWhen certain resins are pyrolized they transform into a glassy polymeric carbon (GPC) with no change in shape. Using this process we have made all-carbon heart valves by rapid molding of the component pieces out of precursor resin, assemblage in the resin stage and pyrolysis to at least 1,000°C to form an accurately articulated device. A heart valve with two occluders set in a carbon ring manufactured out of highly polished carbon has been tested with an excellent record of wear, fatigue, resistance and biocompatibility, especially in contact with blood.
2.2 eV Luminescence in GaN
Authors: Hofinann D. M. , Kovalev D. , Steude G. , Volm D. , Meyer B. K. , Xavier C. , Monteiro T. , Pereira E. , Mokov E. N. , Amano H. , Akasaki I. 
Published: April 2011

ABSTRACTThe yellow Luminescence in GaN centered at 2.2 eV has been studied in various epitaxial layers grown by MOVPE on sapphire and by the sandwich sublimation methode on 6H-SiC substrates. The photoluminescence and optically detected magnetic resonance results can be consistently explained by a recombination model involving shallow donors and deep donors.
Magnetic Resonance Studies of Recombination Processes in GaN-Based Light Emitting Diodes
Authors: Carlos W.E. , Glaser E.R. , Kennedy T.A. , Nakamura S. 
Published: April 2011

ABSTRACTMagnetic resonance techniques are used to study the recombination processes in GaN-based light emitting diodes (LEDs). Electrically-detected magnetic resonance (EDMR) and electroluminescence-detected magnetic resonance (ELDMR) results on InGaN/AlGaN double heterostructures are presented for blue and green LEDs. In either technique our signals are dominated by a broad feature that we ascribe to a deep Zn-related acceptor. Our ELDMR measurements show that this is associated with the blue or green emission. Our EDMR measurements resolve a second center that is tentatively identified as a deep donor trap.