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Bilayer Films (bilayer + film)
Selected AbstractsChemically selective soft X-ray patterning of polymersJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2007Jian Wang The chemically selective modification of polymer mixtures by monochromated soft X-rays has been explored using the high-brightness fine-focused 50,nm beam of a scanning transmission X-ray microscope. Four different polymer systems were examined: a polymethylmethacrylate (PMMA) polyacrylonitrile (PAN) bilayer film; a PMMA- blend -PAN microphase-separated film; a poly(MMA- co -AN) copolymer film; and a poly(ethyl cyanoacrylate) homopolymer film. A high level of chemically selective modification was achieved for the PMMA/PAN bilayer; in particular, irradiation at 288.45,eV selectively removed the carbonyl group from PMMA while irradiation at 286.80,eV selectively reduced the nitrile group of PAN, even when these irradiations were carried out at the same (x,y) position of the sample. In the last two homogenous polymer systems, similar amounts of damage to the nitrile and carbonyl groups occurred during irradiation at either 286.80 or 288.45,eV. This is attributed to damage transfer between the C[triple-bond]N and C=O groups mediated by primary electrons, secondary electrons or radical/ionic processes, aided by their close spatial proximity. Although the overall thickness of the bilayer sample at 70,nm is smaller than the lateral line spreading of 100,nm, the interface between the layers appears to effectively block the transport of energy, and hence damage, between the two layers. The origins of the line spreading in homogeneous phases and possible origins of the damage blocking effect of the interface are discussed. To demonstrate chemically selective patterning, high-resolution multi-wavelength patterns were created in the PMMA/PAN bilayer system. [source] Magnetic hysteresis loop in antiferromagnetically coupled bilayer structuresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2008Yan Ma Abstract The hysteresis behavior of a bilayer film system, in which a hard ferromagnetic layer with larger anisotropy and spin-3/2 couples with a soft ferromagnetic layer with smaller anisotropy and spin-1 antiferromagnetically, is studied by using the Ising model and the linear cluster approach. We calculate the magnetic reversal of the soft magnetic layer at low field while keeping the saturated magnetization state of the hard magnetic layer unperturbed, and find a phenomenon of exchange bias. The influences of anisotropy, intralayer exchange in the soft magnetic layer, and the interlayer exchange on the coercivity and exchange bias in the bilayer film are discussed. It is found that increasing the interlayer coupling can enhance the exchange bias of the system, and the easy plane anisotropy in soft magnetic layers can induce the hysteresis loop moving towards positive field. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bilayer Approach to Laser-Induced Thermal Patterning of ,-Conjugated Polymers,ADVANCED MATERIALS, Issue 13 2008Terry J. Gordon Patterns of a fluorescent ,-conjugated polymer (,CP) are obtained by exposure of bilayer films of a NIR-absorbing dye spin cast onto a thermally labile ,CP. Feature sizes of 20 µm are obtained using laser scan speeds as high as 0.9 m s,1. [source] Spectroscopic ellipsometry study of thin diffusion barriers of TaN and Ta for Cu interconnects in integrated circuitsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008S. Rudra Abstract The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV,visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73,8.7 eV and the dielectric functions were simulated using Drude,Lorentz model and effective medium approximation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the ,-phase of Ta, it turned out to be a mixture of ,- and ,-phases with higher contribution of the ,-phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Percolated perpendicular medium of FePt-MgO/MgO bilayer films for ultra-high magnetic recordingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2007An-Cheng Sun Abstract Percolated perpendicular (FePt)100,x -(MgO)x thin films with x = 0,10.07 vol.% were fabricated on glass substrate with MgO(200)underlayer. When the substrate temperature was 580 oC, a significant enhancement in coercivity was observed at 1.23 vol.% of MgO, which was due to the precipitation of MgO in FePt film causing the hindrance in domain wall motion. As the amount of MgO was increased above 1.23 vol.%, the percolated perpendicular structure began to transform into granular perpendicular structure. Meanwhile, the MgO was found to segregate along grain boundaries of FePt grains, leading to the reduction of FePt grain size. As a result the coercivity and ordering parameter became smaller. In this study the percolated perpendicular medium using FePt film with doping adequate amount of MgO has shown possibility to be an efficient method to increase recording density if the film processing conditions are optimized further. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stabilization of glucose oxidase in alginate microspheres with photoreactive diazoresin nanofilm coatingsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2005Rohit Srivastava Abstract The nanoassembly and photo-crosslinking of diazo-resin (DAR) coatings on small alginate microspheres for stable enzyme entrapment is described. Multilayer nanofilms of DAR with poly(styrene sulfonate) (PSS) were used in an effort to stabilize the encapsulation of glucose oxidase enzyme for biosensor applications. The activity and physical encapsulation of the trapped enzyme were measured over 24 weeks to compare the effectiveness of nanofilm coatings and crosslinking for stabilization. Uncoated spheres exhibited rapid loss of activity, retaining only 20% of initial activity after one week, and a dramatic reduction in effective activity over 24 weeks, whereas the uncrosslinked and crosslinked {DAR/PSS}-coated spheres retained more than 50% of their initial activity after 4 weeks, which remained stable even after 24 weeks for the two and three bilayer films. Nanofilms comprising more polyelectrolyte layers maintained higher overall activity compared to films of the same composition but fewer layers, and crosslinking the films increased retention of activity over uncrosslinked films after 24 weeks. These findings demonstrate that enzyme immobilization and stabilization can be achieved by using simple modifications to the layer-by-layer self-assembly technique. © 2005 Wiley Periodicals, Inc. [source] | ||||||||||