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15 Nov 2011

Volume 110, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 110, 102101 (2011); http://dx.doi.org/10.1063/1.3661159 (1 page)

Mark L. Schlossman, Michael Bedzyk, Jonathan Lang, and Paul F. Lyman
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Preface to Special Topic: Selected Papers from The Eleventh International Conference on Surface X-Ray and Neutron Scattering

Mark L. Schlossman, Michael Bedzyk, Jonathan Lang, and Paul F. Lyman

J. Appl. Phys. 110, 102101 (2011); http://dx.doi.org/10.1063/1.3661159 (1 page)

Online Publication Date: 30 November 2011

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Abstract Unavailable
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01.30.Cc Conference proceedings
68.35.Ct Interface structure and roughness
61.05.fg Neutron scattering (including small-angle scattering)
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.70.Ck X-ray scattering
61.05.cf X-ray scattering (including small-angle scattering)

Dynamical theory: Application to spin-echo resolved grazing incidence scattering from periodic structures

Rana Ashkar, W. L. Schaich, V. O. de Haan, A. A. van Well, R. Dalgliesh, J. Plomp, and Roger Pynn

J. Appl. Phys. 110, 102201 (2011); http://dx.doi.org/10.1063/1.3661162 (6 pages) | Cited 1 time

Online Publication Date: 30 November 2011

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Neutron spin-echo resolved grazing incidence scattering (SERGIS) measurements performed on a silicon diffraction grating with a rectangular profile were shown in our previous publications to be well explained by dynamical theory calculations. The theory is based on a Bloch wave expansion of the neutron wavefunction in the periodic layer of the grating, which includes all multiple scattering within that layer. Calculations show that the spin-echo polarization should be very sensitive to the scattering geometry (i.e., incident angle, sample alignment and beam divergence) and the sample specifications (i.e., grating period, groove depth). To test these predictions, SERGIS measurements have been performed on a set of gratings with different specifications in various scattering geometries. In all cases, simulations based on the dynamical theory, with all the parameters set to their known values, are in good agreement with the collected data.
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42.79.Dj Gratings

Thermally induced nanoscale structural and morphological changes for atomic-layer-deposited Pt on SrTiO3(001)

Zhenxing Feng, Steven T. Christensen, Jeffrey W. Elam, Byeongdu Lee, Mark C. Hersam, and Michael J. Bedzyk

J. Appl. Phys. 110, 102202 (2011); http://dx.doi.org/10.1063/1.3661163 (8 pages)

Online Publication Date: 30 November 2011

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Platinum grown by atomic layer deposition (ALD) on SrTiO3(001) surfaces was studied as a function of Pt coverage and post-deposition thermal treatment. The combination of atomic-force microscopy, scanning electron microscopy, x-ray fluorescence, x-ray reflectivity, and grazing-incidence small-angle x-ray scattering reveals significant changes in the nanoscale surface morphology and crystallinity for the differently prepared films. Surfaces with Pt coverages from 1 to 40 monolayers (ML) show different initial morphologies that evolve into different final Pt microstructures after annealing to 800 °C. These distinct nanoscale structural changes are explained by surface diffusion and the surface and interface energies for noble metals on oxides.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Gh Other heat and thermomechanical treatments
68.35.bd Metals and alloys
68.55.A- Nucleation and growth
61.46.Hk Nanocrystals
78.70.Ck X-ray scattering

Thermal transport in thin films measured by time-resolved, grazing incidence x-ray diffraction

D. A. Walko, Y.-M. Sheu, M. Trigo, and D. A. Reis

J. Appl. Phys. 110, 102203 (2011); http://dx.doi.org/10.1063/1.3661164 (4 pages)

Online Publication Date: 30 November 2011

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We use depth- and time-resolved x-ray diffraction to study thermal transport across single crystal Bi films grown on sapphire in order to determine the thermal conductivity of the film and the Kapitza conductance of the interface. Ultrafast Ti:sapphire laser pulses were used to heat the films; x-ray diffraction then measured the film’s lattice expansion. Use of grazing incidence diffraction geometry provided depth sensitivity, as the x-ray angle of incidence was varied near the critical angle. The shift of the film’s Bragg peak position with time was used to determine the film temperature averaged over an x-ray penetration depth that could be selected by choice of the angle of incidence. For films that were thick compared to the laser penetration depth, we observed a large temperature gradient at early times. In this case, measurements with the incident angle near or well above the critical angle were more sensitive to the film conductivity or Kapitza conductance, respectively. For thinner films, however, cooling was dominated by the Kapitza conductance at all accessible time scales.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
73.25.+i Surface conductivity and carrier phenomena
73.61.At Metal and metallic alloys
66.70.Df Metals, alloys, and semiconductors
78.47.D- Time resolved spectroscopy (>1 psec)
68.35.Ja Surface and interface dynamics and vibrations

Structural and morphological characterization of molecular beam epitaxy grown Si/Ge multilayer using x-ray scattering techniques

M. Sharma, M. K. Sanyal, M. K. Mukhopadhyay, M. K. Bera, B. Saha, and P. Chakraborty

J. Appl. Phys. 110, 102204 (2011); http://dx.doi.org/10.1063/1.3661165 (5 pages)

Online Publication Date: 30 November 2011

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Si/Ge multilayers are of great technological importance as is evident from the research studies of the past two decades. Here, we have presented a method for the morphological and structural characterization of such MBE grown epitaxial Si/Ge superlattice structures using simultaneous analysis of x-ray reflectivity and x-ray diffraction data, respectively. The consistent analysis of the data collected in the Indian Beamline at Photon Factory Synchrotron have allowed for the determination of electron density and strain profile as a function of depth.
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68.65.Cd Superlattices
78.70.Ck X-ray scattering
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Ac Multilayers

Surfactant enhanced solid phase epitaxy of Ge/CaF2/Si(111): Synchrotron x-ray characterization of structure and morphology

J. Wollschläger, C. Deiter, C. R. Wang, B. H. Müller, and K. R. Hofmann

J. Appl. Phys. 110, 102205 (2011); http://dx.doi.org/10.1063/1.3661174 (10 pages)

Online Publication Date: 30 November 2011

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The structure and morphology of CaF2/Si(111) and Ge/CaF2/Si(111) layered structures with film thicknesses in the range of very few nanometers has been studied with synchrotron-based radiation. While the CaF2 film is grown via molecular beam epitaxy, the Ge film is fabricated by surfactant enhanced solid phase epitaxy with Sb as surfactant. The CaF2 film forms two laterally separated phases of relaxed CaF2 and pseudomorphic CaF2, respectively, although the film thickness is very homogeneous. The Ge film is completely relaxed and forms A-oriented parts as well as B-oriented parts, due to twinning. In spite of the large surface roughness of the Ge film, it completely wets CaF2/Si(111) also after annealing at 600 °C, due to the application of Sb during the annealing process.
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81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Np Solid phase epitaxy; growth from solid phases
81.40.Gh Other heat and thermomechanical treatments
68.55.ag Semiconductors
68.47.Fg Semiconductor surfaces

Interface structure of the rubrene crystal field effect transistor

Yusuke Wakabayashi, Jun Takeya, and Tsuyoshi Kimura

J. Appl. Phys. 110, 102206 (2011); http://dx.doi.org/10.1063/1.3661523 (3 pages)

Online Publication Date: 30 November 2011

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The gate voltage effect on the surface structure of a rubrene field effect transistor (FET) is investigated by means of x-ray crystal truncation rod (CTR) scattering. Gate voltage ranging between 0 V and −70 V does not alter the CTR intensity profile of the rubrene FET, which reflects both the rubrene–air interface and the rubrene–substrate interface structures. Two possible structural models that explain the experimental results are proposed: (1) the gate voltage does not affect the structures of the two interfaces, or (2) the gate voltage does not affect the structure of the rubrene–air interface, and the other interface does not contribute to the CTR profile, because of the embossing of the rough substrate surface to the flat rubrene crystal surface.
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85.30.Tv Field effect devices

Self organization of magnetic nanoparticles: A polarized grazing incidence small angle neutron scattering and grazing incidence small angle x-ray scattering study

Katharina Theis-Bröhl, Durgamadhab Mishra, Boris P. Toperverg, Hartmut Zabel, Britta Vogel, Anna Regtmeier, and Andreas Hütten

J. Appl. Phys. 110, 102207 (2011); http://dx.doi.org/10.1063/1.3661654 (5 pages)

Online Publication Date: 30 November 2011

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Cobalt and magnetite nanoparticles were studied with small-angle x-ray and neutron scattering methods under grazing incidence for analyzing their structural and magnetic correlation on silicon substrates. The Co nanoparticles are in the ferromagnetic state while the iron oxide nanoparticles are superparamagnetic at room temperature. After spin-coating the iron oxide particles with a diameter of 20 nm and a very narrow size distribution of only 6% show very nice self-ordering on silicon substrates with nearly perfect six-fold symmetry as can be derived from scanning electron microscopy (SEM) images and from grazing incidence small angle x-ray scattering results. In contrast the dropcasted cobalt nanoparticles show a much higher roughness and less ordering. The corresponding SEM images and grazing incidence small angle neutron scattering maps with polarization of the incident beam reveal less pronounced structural and magnetic correlation.
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75.75.Cd Fabrication of magnetic nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.Ck X-ray scattering
81.16.Dn Self-assembly

In-situ x-ray diffraction studies on post-deposition vacuum-annealing of ultra-thin iron oxide films

F. Bertram, C. Deiter, K. Pflaum, M. Suendorf, C. Otte, and J. Wollschläger

J. Appl. Phys. 110, 102208 (2011); http://dx.doi.org/10.1063/1.3661655 (5 pages) | Cited 1 time

Online Publication Date: 30 November 2011

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A maghemite (γ-Fe2O3) film of 8.3 nm thickness is epitaxially grown on MgO(001) single crystal substrate by reactive molecular beam epitaxy. Chemical composition and crystal structure of the surface was studied by x-ray photoelectron spectroscopy and low energy electron diffraction, respectively. Afterwards the sample was moved to a heating cell for in situ x-ray diffraction experiments on the post-deposition annealing process in high-vacuum to study structural phase transitions of the iron oxide film. The iron oxide film is reduced with increasing temperature. This reduction occurs in two steps that are accompanied by structural transitions. The first step is a reduction from γ-Fe2O3 to Fe3O4 at 360 °C and the second step is the reduction from Fe3O4 to FeO at 410 °C.
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68.55.at Other materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Gh Other heat and thermomechanical treatments
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.35.bt Other materials

Quick measurement of crystal truncation rod profiles in simultaneous multi-wavelength dispersive mode

T. Matsushita, T. Takahashi, T. Shirasawa, E. Arakawa, H. Toyokawa, and H. Tajiri

J. Appl. Phys. 110, 102209 (2011); http://dx.doi.org/10.1063/1.3661656 (8 pages)

Online Publication Date: 30 November 2011

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To conduct time-resolved measurements in the wide momentum transfer (q = 4π sinθ/λ, θ: the glancing angle of the x-ray beam, λ: x-ray wavelength) range of interest, we developed a method that can simultaneously measure the whole profile of x-ray diffraction and crystal truncation rod scattering of interest with no need of rotation of the specimen, detector, and monochromator crystal during the measurement. With a curved crystal polychromator (Si 111 diffraction), a horizontally convergent x-ray beam having a one-to-one correlation between wavelength (energy: 16.24–23.0 keV) and direction is produced. The convergent x-ray beam components of different wavelengths are incident on the specimen in a geometry where θ is the same for all the x-ray components and are diffracted within corresponding vertical scattering planes by a specimen ([GaAs(12ML)/AlAs(8 ML)]50 on GaAs(001) substrate) placed at the focal point. Although θ is the same for all the directions, q continuously varies because λ changes as a function of direction. The normalized horizontal intensity distribution across the beam, as measured using a two-dimensional pixel array detector downstream of the specimen, represents the reflectivity curve profile both near to and far from the Bragg point. As for the crystal truncation rod scattering around the 002 reflection, the diffraction profile from the Bragg peak down to reflectivity of 1.0 × 10−9 was measured with a sufficient data collection time (1000–2000 s). With data collection times of 100, 10, 1.0, and 0.1 s, profiles down to a reflectivity of ∼6 × 10−9, ∼2 × 10−8, ∼8 × 10−8, and ∼8 × 10−7 were measured, respectively. To demonstrate the time-resolving capability of the system, reflectivity curves were measured with time resolutions of 1.0 s while rotating the specimen. We have also measured the diffraction profile around the 113 reflection in the non-specular reflection geometry.
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07.85.-m X- and γ-ray instruments
78.70.Ck X-ray scattering

In situ observation of x-ray irradiation effect by using a multiwave x-ray diffraction phenomenon

Wataru Yashiro, Yoshitaka Yoda, Kazushi Miki, and Toshio Takahashi

J. Appl. Phys. 110, 102210 (2011); http://dx.doi.org/10.1063/1.3661891 (7 pages)

Online Publication Date: 30 November 2011

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In situ observation of the complex scattering amplitude of x-ray specular reflection (amplitude reflectivity) was performed by using a method with a multiwave x-ray diffraction phenomenon. The method can be applied to the noncrystalline layers on a single crystal and allows us to determine its amplitude reflectivity with only a 0.01 degree of crystal rotation, that is, the area irradiated by the incident x rays is almost unchanged during the measurement. We used this method to observe an irradiation effect induced by monochromatic synchrotron x-rays that occurred on a Si(001) single crystal covered with a native oxide layer. The obtained time evolution of the amplitude reflectivities exhibited counterclockwise behavior in the complex plane, indicating that the thickness of the noncrystalline layer on the crystalline substrate was increased by the irradiation.
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61.80.Cb X-ray effects
61.82.Fk Semiconductors

In situ imaging of orthoclase–aqueous solution interfaces with x-ray reflection interface microscopy

P. Fenter, S. S. Lee, Z. Zhang, and N. C. Sturchio

J. Appl. Phys. 110, 102211 (2011); http://dx.doi.org/10.1063/1.3661978 (9 pages)

Online Publication Date: 30 November 2011

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The use of x-ray reflection interface microscopy (XRIM) to image molecular-scale topography at the aqueous–solid interface, in situ, is described. Specifically, we image interfacial topography of the orthoclase-(001)–aqueous solution interface at room temperature and describe the challenges associated with in situ XRIM imaging. The measurements show that the reflectivity signal for in situ XRIM measurements is substantially smaller than that for ex situ measurements, because of both intrinsic and extrinsic factors. There is also a systematic temporal reduction in the image intensity with increasing x-ray dose, revealing that interaction of the focused x-ray beam with the orthoclase interfaces leads to interfacial perturbations, presumably in the form of surface roughening. This image fading is localized to the x-ray beam footprint, suggesting that the primary damage mechanism is initiated by photoelectrons produced by x-ray beam absorption near the substrate–electrolyte interface. Finally, the role of aqueous solution composition in controlling the sensitivity of the orthoclase surface to x-ray beam-induced effects is explored. A substantial increase in the orthoclase (001) surface stability was observed in solutions having elevated ionic strength, apparently as a result of the reduced lifetime of radiation chemistry products at these conditions.
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68.08.De Liquid-solid interface structure: measurements and simulations
68.37.Yz X-ray microscopy
82.50.Kx Processes caused by X-rays or γ-rays

When beauty is only skin deep; optimizing the sensitivity of specular neutron reflectivity for probing structure beneath the surface of thin films

Charles F. Majkrzak, Elisabeth Carpenter, Frank Heinrich, and Norman F. Berk

J. Appl. Phys. 110, 102212 (2011); http://dx.doi.org/10.1063/1.3661979 (14 pages)

Online Publication Date: 30 November 2011

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Specular neutron reflectometry has become an established probe of the nanometer scale structure of materials in thin film and multilayered form. It has contributed especially to our understanding of soft condensed matter of interest in polymer science, organic chemistry, and biology and of magnetic hard condensed matter systems. In this paper we examine a number of key factors which have emerged that can limit the sensitivity of neutron reflection as such a probe. Among these is loss of phase information, and we discuss how knowledge about material surrounding a film of interest can be applied to help resolve the problem. In this context we also consider what role the quantum phenomenon of interaction-free measurement might play in enhancing the statistical efficiency for obtaining reflectivity or transmission data.
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61.05.fj Neutron reflectometry
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology
68.65.Ac Multilayers

A comparative study of Langmuir surfactant films: Grazing incidence x-ray off-specular scattering vs. x-ray specular reflectivity

Yeling Dai, Binhua Lin, Mati Meron, Kyungil Kim, Brian Leahy, and Oleg G. Shpyrko

J. Appl. Phys. 110, 102213 (2011); http://dx.doi.org/10.1063/1.3661980 (6 pages)

Online Publication Date: 30 November 2011

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Surface monolayers assembled on a liquid sub-phase represent a class of systems that is of great interest for studies of phase transitions in quasi-2D systems, chemical self-assembly, surfactant behavior, and biologically relevant monolayers and membranes. X-ray scattering is ideal for studying structural, dynamic, and mechanical properties of these surface monolayers at nanoscale due to the penetrating ability and short wavelength of x-rays. We show here that grazing incidence x-ray off-specular scattering (GIXOS) provides rapid access to in-plane and out-of-plane nanoscale structure, surface fluctuating modes, and potentially bending stiffness. We show that analysis of GIXOS data is highly sensitive to resolution effects. We further present detailed analysis of GIXOS from phospholipid 1,2-dipalmitoyl-phosphatidyl-choline C40H80NO8P (DPPC) and obtain quantitative, angstrom-resolution details of electron density profile normal to the surface that is comparable to those that are obtained from specular x-ray reflectivity measurements. We compare these GIXOS results to x-ray reflectivity measurements performed on the same samples. While electron density and main structural characteristics (such as monolayer thickness) obtained by GIXOS agree with x-ray reflectivity results, the interfaces of GIXOS-derived density profiles are found to be systematically sharper than those obtained with x-ray reflectivity. The possible reasons for these differences are discussed.
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78.70.Ck X-ray scattering
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.46.-w Structure of nanoscale materials
68.18.-g Langmuir-Blodgett films on liquids
68.60.Bs Mechanical and acoustical properties

X-ray fluorescence from a model liquid/liquid solvent extraction system

Wei Bu, Binyang Hou, Miroslav Mihaylov, Ivan Kuzmenko, Binhua Lin, Mati Meron, L. Soderholm, Guangming Luo, and Mark L. Schlossman

J. Appl. Phys. 110, 102214 (2011); http://dx.doi.org/10.1063/1.3661983 (6 pages)

Online Publication Date: 30 November 2011

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X-ray fluorescence near total reflection (XFNTR) is measured from the liquid/liquid interface between dodecane and an ErCl3 aqueous solution by monitoring L shell Er emission lines. A custom sample cell is used to minimize absorption of the fluorescence x-rays that pass through dodecane on their way to the detector. The Er3+ concentration near the interface is related to the fluorescence intensity by a scale factor that is extracted by fitting the incident-angle dependent Er Lα emission line intensities for different ErCl3 bulk concentrations. As an application, we present the use of XFNTR to monitor the growth of interfacial crud in a model solvent extraction system consisting of an interface between a dodecane solution of bis(2-ethylhexyl) phosphate (HDEHP) and an ErCl3 aqueous solution.
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78.55.Bq Liquids
64.75.Ef Mixing
68.05.-n Liquid-liquid interfaces

Configuration of membrane-bound proteins by x-ray reflectivity

Chiu-Hao Chen, Šárka Málková, Wonhwa Cho, and Mark L. Schlossman

J. Appl. Phys. 110, 102215 (2011); http://dx.doi.org/10.1063/1.3661985 (4 pages)

Online Publication Date: 30 November 2011

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In this presentation we review our recent work using x-ray reflectivity to determine the configuration of membrane-bound proteins. The reflectivity data is analyzed in terms of the known crystallographic structure of proteins and a slab model representing the lipid layer to yield an electron density profile of the lipid/protein system. Our recent modified analysis methodology for the lipid/protein system is concisely described in this report. In addition, some results of the configuration of the membrane-bound proteins cPLA2α-C2, p40phox-PX, and PKCα-C2 are highlighted.
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87.15.B- Structure of biomolecules
87.16.dt Structure, static correlations, domains, and rafts
36.20.Hb Configuration (bonds, dimensions)
87.14.Cc Lipids
87.14.ep Membrane proteins

Continuous distribution model for the investigation of complex molecular architectures near interfaces with scattering techniques

Prabhanshu Shekhar, Hirsh Nanda, Mathias Lösche, and Frank Heinrich

J. Appl. Phys. 110, 102216 (2011); http://dx.doi.org/10.1063/1.3661986 (12 pages)

Online Publication Date: 30 November 2011

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Biological membranes are composed of a thermally disordered lipid matrix and therefore require non-crystallographic scattering approaches for structural characterization with x-rays or neutrons. Here we develop a continuous distribution (CD) model to refine neutron or x-ray reflectivity data from complex architectures of organic molecules. The new model is a flexible implementation of the composition-space refinement of interfacial structures to constrain the resulting scattering length density profiles. We show this model increases the precision with which molecular components may be localized within a sample, with a minimal use of free model parameters. We validate the new model by parameterizing all-atom molecular dynamics (MD) simulations of bilayers and by evaluating the neutron reflectivity of a phospholipid bilayer physisorbed to a solid support. The determination of the structural arrangement of a sparsely-tethered bilayer lipid membrane (stBLM) comprised of a multi-component phospholipid bilayer anchored to a gold substrate by a thiolated oligo(ethylene oxide) linker is also demonstrated. From the model we extract the bilayer composition and density of tether points, information which was previously inaccessible for stBLM systems. The new modeling strategy has been implemented into the ga_refl reflectivity data evaluation suite, available through the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR).
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87.16.dr Assembly and interactions
87.16.dt Structure, static correlations, domains, and rafts
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
87.14.Cc Lipids
87.64.Bx Electron, neutron and x-ray diffraction and scattering
87.15.ap Molecular dynamics simulation

Modeling and small-angle neutron scattering spectra of chromatin supernucleosomal structures at genome scale

Andrey V. Ilatovskiy, Dmitry V. Lebedev, Michael V. Filatov, Mikhail Grigoriev, Michael G. Petukhov, and Vladimir V. Isaev-Ivanov

J. Appl. Phys. 110, 102217 (2011); http://dx.doi.org/10.1063/1.3661987 (9 pages)

Online Publication Date: 30 November 2011

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Eukaryotic genome is a highly compacted nucleoprotein complex organized in a hierarchical structure based on nucleosomes. Detailed organization of this structure remains unknown. In the present work we developed algorithms for geometry modeling of the supernucleosomal chromatin structure and for computing distance distribution functions and small-angle neutron scattering (SANS) spectra of the genome-scale (∼106 nucleosomes) chromatin structure at residue resolution. Our physical nucleosome model was based on the mononucleosome crystal structure. A nucleosome was assumed to be rigid within a local coordinate system. Interface parameters between nucleosomes can be set for each nucleosome independently. Pair distance distributions were computed with Monte Carlo simulation. SANS spectra were calculated with Fourier transformation of weighted distance distribution; the concentration of heavy water in solvent and probability of H/D exchange were taken into account. Two main modes of supernucleosomal structure generation were used. In a free generation mode all interface parameters were chosen randomly, whereas nucleosome self-intersections were not allowed. The second generation mode (generation in volume) enabled spherical or cubical wall restrictions. It was shown that calculated SANS spectra for a number of our models were in general agreement with available experimental data.
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87.15.B- Structure of biomolecules
87.80.St Genomic techniques
02.30.Nw Fourier analysis
36.20.Fz Constitution (chains and sequences)
87.14.E- Proteins
87.15.ak Monte Carlo simulations

Governing factors in stress response of nanoparticle films on water surface

Kyungil Kim, Brian D. Leahy, Yeling Dai, Oleg Shpyrko, Janet S. Soltau, Matthew Pelton, Mati Meron, and Binhua Lin

J. Appl. Phys. 110, 102218 (2011); http://dx.doi.org/10.1063/1.3661988 (7 pages)

Online Publication Date: 30 November 2011

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The mechanical properties of self-assembled silver nanoparticle (Ag-NP) films at the air-liquid interface are studied using both visible light optics and x-ray scattering techniques. The response of such films to compression is compared with results from previously studied gold nanoparticle (Au-NP) films, showing many similarities, along with significant differences. Possible factors governing the stress response of nanoparticle films are discussed.
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68.60.Bs Mechanical and acoustical properties
78.40.Kc Metals, semimetals, and alloys
78.66.Bz Metals and metallic alloys
78.70.Ck X-ray scattering
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Specific bilayer on the surface of water-based ferrofluids: Structure and particular persistence

A. Vorobiev, O. Konovalov, A. Khassanov, D. Orlova, and G. Gordeev

J. Appl. Phys. 110, 102219 (2011); http://dx.doi.org/10.1063/1.3661989 (5 pages)

Online Publication Date: 30 November 2011

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The structure of sterically stabilized water-based ferrofluid in the vicinity of free interface with a gaseous atmosphere is studied by means of X-ray reflectometry and grazing incidence X-ray diffraction. Experimental data unambiguously show that in-depth distribution of the magnetic nano-particles and surfactant molecules in the ferrofluid layer close to the interface is essentially non-uniform. Particularly, bulk homogeneous liquid is covered with a relatively thick layer (about 200 Å) with enhanced concentration of the surfactant and reduced concentration of the magnetic particles, which is consequently overlayed with a thin layer (about 40 Å) with increased concentration of the particles. Having the aim to obtain more homogeneous and controllable ferrofluid surface, we tried to eliminate this specific bilayer in two different ways—mechanically and by means of long-term sedimentation of a sample in a dropping funnel under hexadecane. However, in both case the same surface structure but with slightly different parameters have been observed. Apparently, the described bilayer can be assumed as an essential equilibrium feature inevitably existing at the interface of water-based ferrofluids with gas.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
75.75.-c Magnetic properties of nanostructures
68.15.+e Liquid thin films
75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials

Interfaces in organic devices studied with resonant soft x-ray reflectivity

Hongping Yan, Cheng Wang, Andres Garcia, Sufal Swaraj, Ziran Gu, Christopher R. McNeill, Torben Schuettfort, Karen E. Sohn, Edward J. Kramer, Guillermo C. Bazan, Thuc-Quyen Nguyen, and Harald Ade

J. Appl. Phys. 110, 102220 (2011); http://dx.doi.org/10.1063/1.3661991 (9 pages) | Cited 1 time

Online Publication Date: 30 November 2011

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Interfaces between donor and acceptor semiconducting polymers are critical to the performance of polymer light-emitting diodes and organic solar cells. Similarly, interfaces between a conjugated polymer and a dielectric play a critical role in organic thin-film transistors. Often, these interfaces are difficult to characterize with conventional methods. Resonant soft x-ray reflectivity (R-SoXR) is a unique and relatively simple method to investigate such interfaces. R-SoXR capabilities are exemplified by presenting or discussing results from systems spanning all three device categories. We also demonstrate that the interfacial widths between active layers can be controlled by annealing at elevated temperature, pre-annealing of the bottom layer, or casting from different solvent mixtures. The extension of R-SoXR to the fluorine K absorption edge near 698 eV is also demonstrated.
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85.60.Jb Light-emitting devices
88.40.jr Organic photovoltaics
85.30.Tv Field effect devices

Manipulating thin polymer films by changing the pH value

D. C. Florian Wieland, Patrick Degen, Michael Paulus, Martin A. Schroer, Heinz Rehage, and Metin Tolan

J. Appl. Phys. 110, 102221 (2011); http://dx.doi.org/10.1063/1.3661992 (4 pages)

Online Publication Date: 30 November 2011

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Show Abstract
The structural change of Langmuir layers composed of alkyltrichlorosilanes under the influence of ammonia (NH3) was investigated. X-ray reflectivity and grazing incidence diffraction measurements along with surface pressure and surface potential measurements were performed in order to characterize the network structure. The data show an increase of the scattered intensity after addition of ammonia while the domain and unit cell size of the film did not change. These results show a higher surface coverage, which is not caused by a simple compression of the lipid tails. The effect can be attributed to a closing of voids in the polymer film caused by temporary breaking and annealing of the chemical bonds in the network by an increase of pH.
Show PACS
82.45.Mp Thin layers, films, monolayers, membranes
82.45.Wx Polymers and organic materials in electrochemistry
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
82.45.-h Electrochemistry and electrophoresis
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