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Andrew Doran - One of the best experts on this subject based on the ideXlab platform.

  • interplay between intrinsic and stacking fault magnetic domains in bi layered manganites
    Applied Physics Letters, 2012
    Co-Authors: M Hossain, Andrew Doran, A Scholl, Mark H Burkhardt, S Sarkar, Hendrik Ohldag, Y D Chuang, A T Young, D S Dessau, H Zheng
    Abstract:

    We present a low temperature x-ray Photoemission Electron Microscopy study of the bi-layered manganite compound La1.2Sr1.8Mn2O7 (BL-LSMO) to investigate the influence of stacking faults, which are structurally and magnetically different from the bi-layered host. In BL-LSMO, small magnetic moment persists to T*=300 K, well above the Curie temperature of 120 K (TC). Our magnetic images show that 3D stacking faults are responsible for the T* transition. Furthermore, close to the TC, stacking faults are well coupled to the bi-layered host with latter magnetic domains controlling the spin direction of the stacking faults. Contrary to recent reports, we find that stacking faults do not seed magnetic domains in the host via an exchange spring mechanism and the intrinsic TC of the BL-LSMO is not lower than 120 K.

  • stripe to bubble transition of magnetic domains at the spin reorientation of fe ni cu ni cu 001
    Physical Review B, 2009
    Co-Authors: Jianzhong Wu, Y Z Wu, Andrew Doran, Jong Hyun Choi, A Scholl, Chanyong Hwang
    Abstract:

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using Photoemission Electron Microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  • magnetic bubble domain phase at the spin reorientation transition of ultrathin fe ni cu 001 film
    Physical Review Letters, 2007
    Co-Authors: Jong Hyun Choi, Andrew Doran, T Owens, A Scholl, C Won, Z Q Qiu
    Abstract:

    Magnetic domain phases of ultrathin Fe/Ni/Cu(001) are studied using Photoemission Electron Microscopy at the spin reorientation transition (SRT). We observe a new magnetic phase of bubble domains within a narrow SRT region after applying a nearly in-plane magnetic field pulse to the sample. By applying the magnetic field pulse along different directions, we find that the bubble domain phase exists only if the magnetic field direction is less than approximately 10 degrees relative to the sample surface. A temperature dependent measurement shows that the bubble domain phase becomes unstable above 370 K.

  • nanoscale x ray magnetic circular dichroism probing of electric field induced magnetic switching in multiferroic nanostructures
    Applied Physics Letters, 2007
    Co-Authors: T Zhao, Andrew Doran, A Scholl, F Zavaliche, Haimei Zheng, M Barry, Kilho Lee, M P Cruz, R Ramesh
    Abstract:

    The magnetic structure as well as its response to an external electric field were studied in ferrimagnetic CoFe2O4 nanopillars embedded in an epitaxial ferroelectric BiFeO3 film using Photoemission Electron Microscopy and x-ray magnetic circular dichroism. Magnetic switching was observed in both Co and Fe magnetic sublattices after application of an electric field. About 50% of the CoFe2O4 nanopillars were measured to switch their magnetization with the electric field, implying an elastic-mediated electric-field-induced magnetic anisotropy change.

  • magnetic stripe melting at the spin reorientation transition in fe ni cu 001
    Physical Review B, 2005
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran, T Owens, Jong Hyun Choi, Jianzhong Wu, Hengcan Zhao
    Abstract:

    Magnetic stripe domains in Fe/Ni/Cu(001) were imaged andstudied using Photoemission Electron Microscopy. The stripe domain widthdecreases exponentially as the system approaches the spin reorientationtransition SRT point. A reduction of the Curie temperature TC is observedwithin a narrow gap of the SRT region. For film with fixed thickness, thestripe domains below TC represent only part of the stripe phase due to ahigher SRT temperature than TC.

Andreas Scholl - One of the best experts on this subject based on the ideXlab platform.

  • observation of current driven oscillatory domain wall motion in ni80fe20 co bilayer nanowire
    Applied Physics Letters, 2013
    Co-Authors: Wen Zhang, Andreas Scholl, Ping Kwan Johnny Wong, Peng Yan, Simon A Morton, Xiangrong Wang, A Young, I Barsukov, M Farle, G Van Der Laan
    Abstract:

    Direct observation of current-driven oscillatory domain wall motion above the Walker breakdown by x-ray magnetic circular dichroism in Photoemission Electron Microscopy is reported in Ni80Fe20/Co nanowire, showing micrometer-scale displacement at ∼13 MHz. We identify two key factors that enhance the oscillatory motion: (i) increase of the hard-axis magnetic anisotropy field value |H⊥| and (ii) increase of the ratio between non-adiabatic spin-transfer parameter to the Gilbert damping coefficient, β/α, which is required to be larger than 1. These findings point to an important route to tune the long-scale oscillatory domain wall motion using appropriate geometry and materials.

  • electrical control of antiferromagnetic domains in multiferroic bifeo3 films at room temperature
    Nature Materials, 2006
    Co-Authors: Andreas Scholl, T Zhao, F Zavaliche, M Barry, M P Cruz, Kunwoo Lee, A Doran, Yinghao Chu
    Abstract:

    Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. In this work, we demonstrate the first observation of electrical control of antiferromagnetic domain structure in a single-phase multiferroic material at room temperature. High-resolution images of both antiferromagnetic and ferroelectric domain structures of (001)-oriented multiferroic BiFeO3 films revealed a clear domain correlation, indicating a strong coupling between the two types of order. The ferroelectric structure was measured using piezo force Microscopy, whereas X-ray Photoemission Electron Microscopy as well as its temperature dependence was used to detect the antiferromagnetic configuration. Antiferromagnetic domain switching induced by ferroelectric polarization switching was observed, in agreement with theoretical predictions.

  • interface coupling transition in a thin epitaxial antiferromagnetic film interacting with a ferromagnetic substrate
    Physical Review Letters, 2006
    Co-Authors: Marco Finazzi, Andreas Scholl, Alberto Brambilla, Paolo Biagioni, J Graf, G H Gweon, Alessandra Lanzara, Lamberto Duo
    Abstract:

    We report experimental evidence for a transition in the interface coupling between an antiferromagnetic film and a ferromagnetic substrate. The transition is observed in a thin epitaxial NiO film grown on top of Fe(001) as the film thickness is increased. Photoemission Electron Microscopy excited with linearly polarized x rays shows that the NiO film is antiferromagnetic at room temperature with in-plane uniaxial magnetic anisotropy. The anisotropy axis is perpendicular to the Fe substrate magnetization when the NiO thickness is less than about 15 A, but rapidly becomes parallel to the Fe magnetization for a NiO coverage higher than 25 A.

  • magnetic stripe melting at the spin reorientation transition in fe ni cu 001
    Physical Review B, 2005
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran, T Owens, Jong Hyun Choi, Jianzhong Wu, Hengcan Zhao
    Abstract:

    Magnetic stripe domains in Fe/Ni/Cu(001) were imaged andstudied using Photoemission Electron Microscopy. The stripe domain widthdecreases exponentially as the system approaches the spin reorientationtransition SRT point. A reduction of the Curie temperature TC is observedwithin a narrow gap of the SRT region. For film with fixed thickness, thestripe domains below TC represent only part of the stripe phase due to ahigher SRT temperature than TC.

  • magnetic stripe domains in coupled magnetic sandwiches
    Physical Review Letters, 2004
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran
    Abstract:

    : Magnetic stripe domains in the spin reorientation transition region are investigated in (Fe/Ni)/Cu(001) and Co/Cu/(Fe/Ni)/Cu(001) using Photoemission Electron Microscopy. For (Fe/Ni)/Cu(001), the stripe domain width decreases exponentially as the Fe/Ni film approaches the spin reorientation transition point. For Co/Cu/(Fe/Ni)/Cu(001), the Fe/Ni stripe orientation is aligned with the Co in-plane magnetization, and the stripe domain width decreases exponentially with increasing the interlayer coupling between the Fe/Ni and Co films. By considering magnetic stripes within an in-plane magnetic field, we reveal a universal dependence of the stripe domain width on the magnetic anisotropy and on the interlayer coupling.

U Kleineberg - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional characterization of extreme ultraviolet mask blank defects by interference contrast Photoemission Electron Microscopy
    Optics Express, 2008
    Co-Authors: Jingquan Lin, N. Weber, J Maul, M Merkel, M Escher, Hakseung Han, Stefan Wurm, G Schonhense, U Kleineberg
    Abstract:

    A Photoemission Electron microscope based on a new contrast mechanism “interference contrast” is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast Photoemission Electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

  • at wavelength inspection of sub 40 nm defects in extreme ultraviolet lithography mask blank by Photoemission Electron Microscopy
    Optics Letters, 2007
    Co-Authors: Jingquan Lin, N. Weber, J Maul, Stefan Hendel, Karsten Rott, M Merkel, G Schoenhense, U Kleineberg
    Abstract:

    A new at-wavelength inspection technology to probe nanoscale defects buried underneath Mo/Si multilayers on an extreme ultraviolet (EUV) lithography mask blank has been implemented using EUV Photoemission Electron Microscopy (EUV-PEEM). EUV-PEEM images of programmed defect structures of various lateral and vertical sizes recorded at an ~13.5 nm wavelength show that 35 nm wide and 4 nm high buried line defects are clearly detectable. The imaging technique proves to be sensitive to small phase jumps, enhancing the edge visibility of the phase defects, which is explained in terms of a standing wave enhanced image contrast at resonant EUV illumination.

  • actinic extreme ultraviolet lithography mask blank defect inspection by Photoemission Electron Microscopy
    Journal of Vacuum Science & Technology B, 2006
    Co-Authors: Jingquan Lin, A. Oelsner, G Schoenhense, U Kleineberg, Ulrich Neuhaeusler, J Slieh, Armin Brechling, Ulrich Heinzmann, Dima Valdaitsev, N. Weber
    Abstract:

    A new method for the actinic inspection of defects inside and on top of extreme ultraviolet (EUV) lithography multilayer-coated mask blanks is presented. The experimental technique is based on Photoemission Electron Microscopy supported by the generation of a standing wave field inside and above the multilayer mask blank when illuminated near the resonance Bragg wavelength at around 13.5nm. Experimental results on programed defect samples based on Electron beam lithographic structures or silica balls overcoated with an EUV multilayer show that buried defects with a lateral size down to 50nm are detectable. Furthermore, phase structures as shallow as 6nm in height on a programed phase grating sample have been detected by this technique. The contrast of the phase defect structures has shown to be strongly dependent on and controlled by the phase of the standing wave field at the mask blank surface, and thus can be optimized by tuning the inspection wavelength.

N. Weber - One of the best experts on this subject based on the ideXlab platform.

  • Time-of-flight-photoElectron emission Microscopy on plasmonic structures using attosecond extreme ultraviolet pulses
    Applied Physics Letters, 2012
    Co-Authors: S-h Chew, A. Oelsner, Frederik Sümann, A. Guggenmos, N. Weber, Jochen Schmidt, Andrew Wirth, Sergey Zherebtsov, Catherine Spath, James Kapaldo
    Abstract:

    We report on the imaging of plasmonic structures by time-of-flight-Photoemission Electron Microscopy (ToF-PEEM) in combination with extreme ultraviolet (XUV) attosecond pulses from a high harmonic generation source. Characterization of lithographically fabricated Au structures using these ultrashort XUV pulses by ToF-PEEM shows a spatial resolution of ?200 nm. Energy-filtered imaging of the secondary Electrons resulting in reduced chromatic aberrations as well as microspectroscopic identification of core and valence band Electronic states have been successfully proven. We also find that the fast valence band Electrons are not influenced by space charge effects, which is essentially important for attosecond nanoplasmonic-field Microscopy realization.

  • three dimensional characterization of extreme ultraviolet mask blank defects by interference contrast Photoemission Electron Microscopy
    Optics Express, 2008
    Co-Authors: Jingquan Lin, N. Weber, J Maul, M Merkel, M Escher, Hakseung Han, Stefan Wurm, G Schonhense, U Kleineberg
    Abstract:

    A Photoemission Electron microscope based on a new contrast mechanism “interference contrast” is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast Photoemission Electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

  • at wavelength inspection of sub 40 nm defects in extreme ultraviolet lithography mask blank by Photoemission Electron Microscopy
    Optics Letters, 2007
    Co-Authors: Jingquan Lin, N. Weber, J Maul, Stefan Hendel, Karsten Rott, M Merkel, G Schoenhense, U Kleineberg
    Abstract:

    A new at-wavelength inspection technology to probe nanoscale defects buried underneath Mo/Si multilayers on an extreme ultraviolet (EUV) lithography mask blank has been implemented using EUV Photoemission Electron Microscopy (EUV-PEEM). EUV-PEEM images of programmed defect structures of various lateral and vertical sizes recorded at an ~13.5 nm wavelength show that 35 nm wide and 4 nm high buried line defects are clearly detectable. The imaging technique proves to be sensitive to small phase jumps, enhancing the edge visibility of the phase defects, which is explained in terms of a standing wave enhanced image contrast at resonant EUV illumination.

  • actinic extreme ultraviolet lithography mask blank defect inspection by Photoemission Electron Microscopy
    Journal of Vacuum Science & Technology B, 2006
    Co-Authors: Jingquan Lin, A. Oelsner, G Schoenhense, U Kleineberg, Ulrich Neuhaeusler, J Slieh, Armin Brechling, Ulrich Heinzmann, Dima Valdaitsev, N. Weber
    Abstract:

    A new method for the actinic inspection of defects inside and on top of extreme ultraviolet (EUV) lithography multilayer-coated mask blanks is presented. The experimental technique is based on Photoemission Electron Microscopy supported by the generation of a standing wave field inside and above the multilayer mask blank when illuminated near the resonance Bragg wavelength at around 13.5nm. Experimental results on programed defect samples based on Electron beam lithographic structures or silica balls overcoated with an EUV multilayer show that buried defects with a lateral size down to 50nm are detectable. Furthermore, phase structures as shallow as 6nm in height on a programed phase grating sample have been detected by this technique. The contrast of the phase defect structures has shown to be strongly dependent on and controlled by the phase of the standing wave field at the mask blank surface, and thus can be optimized by tuning the inspection wavelength.

  • high resolution actinic defect inspection for extreme ultraviolet lithography multilayer mask blanks by Photoemission Electron Microscopy
    Applied Physics Letters, 2006
    Co-Authors: U Neuhausler, A. Oelsner, N. Weber, J Slieh, M Brzeska, A Wonisch, T Westerwalbesloh, Hubert Bruckl, M Schicketanz, M Escher
    Abstract:

    We report on the development and first experimental results of a “at wavelength” full-field imaging technique for defect inspection of multilayer mask blanks for extreme ultraviolet (EUV) lithography. According to the International Semiconductor Roadmap by Sematech, less than 5×10−3 defects per cm2 should be present on such multilayer mask blank to enable mass production of microElectronics using EUV lithography, thus fast high-resolution methods for mask defect inspection and localization are needed. Our approach uses a Photoemission Electron microscope in a normal incidence illumination mode at 13 nm to image the photoElectron emission induced by the EUV wave field on the multilayer mask blank surface. We show that by these means, buried defects in the multilayer stack can be probed down to a lateral size of 50 nm.

Y Z Wu - One of the best experts on this subject based on the ideXlab platform.

  • stripe to bubble transition of magnetic domains at the spin reorientation of fe ni cu ni cu 001
    Physical Review B, 2009
    Co-Authors: Jianzhong Wu, Y Z Wu, Andrew Doran, Jong Hyun Choi, A Scholl, Chanyong Hwang
    Abstract:

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using Photoemission Electron Microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  • magnetic stripe melting at the spin reorientation transition in fe ni cu 001
    Physical Review B, 2005
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran, T Owens, Jong Hyun Choi, Jianzhong Wu, Hengcan Zhao
    Abstract:

    Magnetic stripe domains in Fe/Ni/Cu(001) were imaged andstudied using Photoemission Electron Microscopy. The stripe domain widthdecreases exponentially as the system approaches the spin reorientationtransition SRT point. A reduction of the Curie temperature TC is observedwithin a narrow gap of the SRT region. For film with fixed thickness, thestripe domains below TC represent only part of the stripe phase due to ahigher SRT temperature than TC.

  • magnetic stripe domains in coupled magnetic sandwiches
    Physical Review Letters, 2004
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran
    Abstract:

    : Magnetic stripe domains in the spin reorientation transition region are investigated in (Fe/Ni)/Cu(001) and Co/Cu/(Fe/Ni)/Cu(001) using Photoemission Electron Microscopy. For (Fe/Ni)/Cu(001), the stripe domain width decreases exponentially as the Fe/Ni film approaches the spin reorientation transition point. For Co/Cu/(Fe/Ni)/Cu(001), the Fe/Ni stripe orientation is aligned with the Co in-plane magnetization, and the stripe domain width decreases exponentially with increasing the interlayer coupling between the Fe/Ni and Co films. By considering magnetic stripes within an in-plane magnetic field, we reveal a universal dependence of the stripe domain width on the magnetic anisotropy and on the interlayer coupling.

  • magnetic stripe domains in coupled magnetic sandwiches
    Physics, 2004
    Co-Authors: Y Z Wu, Andreas Scholl, Andrew Doran
    Abstract:

    Magnetic stripe domains in the spin reorientation transition region are investigated in (Fe/Ni)/Cu(001) and Co/Cu/(Fe/Ni)/Cu(001) using Photoemission Electron Microscopy. For the former, the stripe domain width decreases exponentially as the Fe/Ni film approaches the transition point. For the latter, the Fe/Ni stripe orientation is aligned with the Co in-plane magnetization and the domain width decreases exponentially with increasing of the interlayer coupling between the Fe/Ni and Co films. By considering magnetic stripes within an in-plane magnetic field, we reveal a universal dependence of the stripe domain width on the magnetic anisotropy and on the interlayer coupling.