Sample records for hf-treated si001 surface

  1. Reactions between monolayer Fe and Si(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, M.; Kobayashi, N.; Hayashi, N. [Electrotechnical Lab., Tsukuba, Ibaraki (Japan)


    Reactions between 1.5 monolayer(ML) Fe deposited on Si(001)-2x1 and -dihydride surfaces were studied in situ by reflection high-energy electron diffraction and time-of-flight ion scattering spectrometry with the use of 25 keV H ions. The reactions between Fe and Si which were successively deposited on Si(001)-dihydride surface were also studied. After the room temperature deposition Fe reacted with Si(001)-2x1 substrate resulting in the formation of polycrystalline Fe5Si3. By annealing to 560-650degC composite heteroepitaxial layer of both type A and type B {beta}-FeSi2 was formed. On the dihydride surface polycrystalline Fe was observed after 1.5ML Fe deposition at room temperature, and reaction between Fe and Si(001)-dihydride surface is not likely at room temperature. We observed 3D rough surface when we deposited only Fe layer on the dihydride surface and annealed above 700degC. The hydrogen termination of Si(001) surface prevents the deposited Fe from diffusing into the substrate below 500degC, however the annealing above 710degC leads to the diffusion. We obtained 2D ordered surface, which showed 3x3 RHEED pattern as referenced to the primitive unreconstructed Si(001) surface net, when we deposited 2.5ML Fe and 5.8ML Si successively onto Si(001)-dihydride surface and annealed to 470degC. (author)

  2. Reaction paths of alane dissociation on the Si(001) surface. (United States)

    Smith, Richard; Bowler, David R


    Building on our earlier study, we examine the kinetic barriers to decomposition of alane, AlH3, on the Si(001) surface, using the nudged elastic band (NEB) approach within DFT. We find that the initial decomposition to AlH with two H atoms on the surface proceeds without a significant barrier. There are several pathways available to lose the final hydrogen, though these present barriers of up to 1 eV. Incorporation is more challenging, with the initial structures less stable in several cases than the starting structures, just as was found for phosphorus. We identify a stable route for Al incorporation following selective surface hydrogen desorption (e.g. by STM tip). The overall process parallels PH3, and indicates that atomically precise acceptor doping should be possible. © 2018 IOP Publishing Ltd.

  3. On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Fatima,; Hossain, Sehtab; Mohottige, Rasika; Oncel, Nuri, E-mail:, E-mail: [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, North Dakota 58202 (United States); Can Oguz, Ismail; Gulseren, Oguz, E-mail:, E-mail: [Department of Physics, Bilkent University, Ankara (Turkey); Çakır, Deniz [Department of Physics, University of Antwerp, Antwerp 2610 (Belgium)


    Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77 K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires.

  4. 3C-SiC nanocrystal growth on 10° miscut Si(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Deokar, Geetanjali, E-mail: [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); D' Angelo, Marie; Demaille, Dominique [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Cavellin, Catherine Deville [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Faculté des Sciences et Technologie UPEC, 61 av. De Gaulle, Créteil F-94010 (France)


    The growth of 3C-SiC nano-crystal (NC) on 10° miscut Si(001) substrate by CO{sub 2} thermal treatment is investigated by scanning and high resolution transmission electron microscopies. The vicinal Si(001) surface was thermally oxidized prior to the annealing at 1100 °C under CO{sub 2} atmosphere. The influence of the atomic steps at the vicinal SiO{sub 2}/Si interface on the SiC NC growth is studied by comparison with the results obtained for fundamental Si(001) substrates in the same conditions. For Si miscut substrate, a substantial enhancement in the density of the SiC NCs and a tendency of preferential alignment of them along the atomic step edges is observed. The SiC/Si interface is abrupt, without any steps and epitaxial growth with full relaxation of 3C-SiC occurs by domain matching epitaxy. The CO{sub 2} pressure and annealing time effect on NC growth is analyzed. The as-prepared SiC NCs can be engineered further for potential application in optoelectronic devices and/or as a seed for homoepitaxial SiC or heteroepitaxial GaN film growth. - Highlights: • Synthesis of 3C-SiC nanocrystals epitaxied on miscut-Si using a simple technique • Evidence of domain matching epitaxy at the SiC/Si interface • SiC growth proceeds along the (001) plane of host Si. • Substantial enhancement of the SiC nanocrystal density due to the miscut • Effect of the process parameters (CO{sub 2} pressure and annealing duration)

  5. Morphological Evolution of Pit-Patterned Si(001) Substrates Driven by Surface-Energy Reduction (United States)

    Salvalaglio, Marco; Backofen, Rainer; Voigt, Axel; Montalenti, Francesco


    Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typical metastable pit morphologies that can be expected on Si(001), depending on the initial depth/shape. Evolution is predicted using a surface-diffusion model, formulated in a phase-field framework, and tackling surface-energy anisotropy. Results are shown to nicely reproduce typical metastable shapes reported in the literature. Moreover, long time scale evolutions of pit profiles with different depths are found to follow a similar kinetic pathway. The model is also exploited to treat the case of heteroepitaxial growth involving two materials characterized by different facets in their equilibrium Wulff's shape. This can lead to significant changes in morphologies, such as a rotation of the pit during deposition as evidenced in Ge/Si experiments.

  6. Optical properties of organically functionalized silicon surfaces: Uracil-like nucleobases on Si(001) (United States)

    Molteni, Elena; Cappellini, Giancarlo; Onida, Giovanni; Fratesi, Guido


    We predict UV reflectance anisotropy spectra (RAS) of the organically functionalized silicon (001) surface covered by pyrimidinic uracil-like nucleobases. First-principles results based on density functional theory show characteristic spectral features appearing in the UV range between 3 and 7 eV, besides the expected quench in the well-known two-minima RAS signal of clean Si(001). Nucleobase adsorption in the energetically favored "dimer bridge" configuration gives rise to a characteristic RAS line shape, common to thymine, uracil, and 5-fluorouracil. We trace back the origin of such spectral features by singling out RAS structures induced by relaxation and passivation effects on the Si surface, and those directly associated with molecular excitations. The former turn out to be the same for the three nucleobases, and are totally unaffected by molecular tilting. The sign and position of the latter RAS peaks at higher energy exhibit a moderate nucleobase dependence, and can be fully rationalized in terms of the molecular orbitals involved. The present theoretical results call for a RAS experimental study in the UV region extending up to ≃6 -7 eV.

  7. Manufacture of surface reaction analysis apparatus and its application to analysis of initial oxidation processes on Si (001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Teraoka, Yuden; Yoshigoe, Akitaka; Sano, Mutsumi [Sychrotron Radiation Research Center, Kansai Research Establishment, Japan Atomic Energy Research Institute, Mikazuki, Hyogo (Japan)


    We have joined with the construction team of JAERI soft x-ray beaming, BL23SU, in the SPring-8. An experimental apparatus for the analysis of surface reaction dynamics on semiconductor surfaces has been manufactured and installed as an end-station of the beamline. This end-station emphasizes a simultaneous use of supersonic molecular beams, an electron energy analyzer and a quadrupole mass analyzer to achieve the real 'in situ' analysis of surface reactions to obtain more deeper understanding for elementary processes of chemisorption. The effects of translational energy of incident O{sub 2} molecules for initial oxidation on Si (001) surfaces have been investigated by photoemission spectroscopy and molecular beam scattering techniques. The oxygen saturation coverage on the Si (001) surface at room temperature increased with increasing the translational energy, showing two thresholds at 1.0 eV and 2.6 eV. These values were close to the predicted values from the first-principles calculation so that the values were assigned to the backbond oxidation of top dimers and subsurface Si atoms, respectively. The oxidation number of Si atoms on the oxygen-chemisorbed Si (001) surface was found to be increased with increasing the incident energy of O{sub 2} molecules. Furthermore, the sudden increase of SiO desorption rate was found at about 700degC in the incident energy larger than 2.0 eV. (author)

  8. Real-time observation of initial stages of thermal oxidation on Si(001) surface by using synchrotron radiation photoemission spectroscopy

    CERN Document Server

    Yoshigoe, A; Moritani, K


    Real-time observation of initial stages of thermal oxidation processes on the Si(001) surface using O sub 2 gas (1x10 sup - sup 4 Pa) was performed by means of the O-1s and Si-2p photoemission spectroscopy with synchrotron radiation. From the analysis of the time evolution of oxygen uptake curves on the basis of the reaction kinetics model, the oxide-layer growth depending on the surface temperature was categorized by the Langmuir adsorption and the auto-catalytic reaction models, respectively. It was found that the oxidation rates increased with increasing the surface temperature. The time evolution of Si oxidation states depending on the surface temperature was well monitored. We found that the surface temperature enhanced the diffusion and/or migration of adsorbed oxygen and the bulk Si atom. (author)

  9. Ethers on Si(001): A prime example for the common ground between surface science and molecular organic chemistry

    KAUST Repository

    Pecher, Lisa


    Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained.

  10. Surface Chemistry of tert-Butylphosphine (TBP) on Si(001) in the Nucleation Phase of Thin-Film Growth. (United States)

    Stegmüller, Andreas; Werner, Katharina; Reutzel, Marcel; Beyer, Andreas; Rosenow, Phil; Höfer, Ulrich; Stolz, Wolfgang; Volz, Kerstin; Dürr, Michael; Tonner, Ralf


    We combine density functional theory calculations and scanning tunneling microscopy investigations to identify the relevant chemical species and reactions in the nucleation phase of chemical vapor deposition. tert-Butylphosphine (TBP) was deposited on a silicon substrate under conditions typical for surface functionalization and growth of semiconductor materials. On the activated hydrogen-covered surface H/Si(001) it forms a strong covalent P-Si bond without loss of the tert-butyl group. Calculations show that site preference for multiple adsorption of TBP is influenced by steric repulsion of the adsorbate's bulky substituent. STM imaging furthermore revealed an anisotropic distribution of TBP with a preference for adsorption perpendicular to the surface dimer rows. The adsorption patterns found can be understood by a mechanism invoking stabilization of surface hydrogen vacancies through electron donation by an adsorbate. The now improved understanding of nucleation in thin-film growth may help to optimize molecular precursors and experimental conditions and will ultimately lead to higher quality materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ethers on Si(001): A prime example for the common ground between surface science and molecular organic chemistry. (United States)

    Pecher, Lisa; Laref, Slimane; Raupach, Marc; Tonner, Ralf Ewald


    Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Real-time monitoring of initial thermal oxidation on Si(001) surfaces by synchrotron radiation photoemission spectroscopy

    CERN Document Server

    Yoshigoe, A; Teraoka, Y


    The thermal oxidation of Si(001) surfaces at 860 K, 895 K, 945 K and 1000 K under the O sub 2 pressure of 1 x 10 sup - sup 4 Pa has been investigated by time-resolved photoemission measurements with synchrotron radiation. Based on time evolution analyses by reaction kinetics models, it was found that the oxidation at 860 K, 895 K and 945 K has progressed with the Langmuir adsorption type, whereas the oxidation at 1000 K has showed the character of the two-dimensional island growth involving SiO desorption. The oxidation rates increases with increasing surface temperature in the passive oxidation condition. The time evolution of each Si oxidation state (Si sup n sup + : n = 1, 2, 3, 4) derived from the Si-2p core-level shifts has also been analyzed. The results revealed that the thermal energy contribution to the migration process of the adsorbed oxygen and the emission of the bulk silicon atoms. Thus, the fraction of the Si sup 4 sup + bonding state, i.e. SiO sub 2 structure, was increased. (author)

  13. Time-resolved two-photon photoemission at the Si(001)-surface. Hot electron dynamics and two-dimensional Fano resonance; Zeitaufgeloeste Zweiphotonen-Photoemission an der Si(001)-Oberflaeche. Dynamik heisser Elektronen und zweidimensionaler Fano-Effekt

    Energy Technology Data Exchange (ETDEWEB)

    Eickhoff, Christian


    By combining ultrafast laser excitation with energy-, angle- and time-resolved twophoton photoemission (2PPE), the electronic properties of bulk silicon and the Si(001) surface are investigated in this thesis. A custom-built laser- and UHV-systemequipped with a display type 2D-CCD-detector gives new insight into the relaxation dynamics of excited carriers on a femtosecond timescale. The bandgap between occupied valence bands and unoccupied conduction bands characteristically influences the dynamics of excited electrons in the bulk, as well as in surface states and resonances. For the electron-phonon interaction this leads to the formation of a bottleneck during the relaxation of hot electrons in the conduction band, which maintains the elevated electronic temperature for several picoseconds. During relaxation, excited electrons also scatter from the conduction band into the unoccupied dangling-bond surface state D{sub down}. Depending on the excitation density this surface recombination is dominated by electron-electron- or electron-phonon scattering. The relaxation of the carriers in the D{sub down}-band is again slowed down by the formation of a bottleneck in electron-phonon coupling. Furthermore, the new laser system has allowed detection of the Rydberg-like series of image-potential resonances on the Si(001)-surface. It is shown that the lifetime of these image-potential resonances in front of the semiconducting surface exhibits the same behavior as those in front of metallic surfaces. Moreover the electron-phonon coupling in the first image-potential resonance was investigated and compared to the D{sub down}-surface state. For the first time, Fano-type lineprofiles are demonstrated and analyzed in a 2PPEprocess on a surface. Tuning the photon energy of the pump-laser across the resonance between the occupied dangling-bond state D{sub up}, and the unoccupied image-potential resonance n=1, reveals a clear intensity variation that can be successfully described

  14. Electric field-induced metallic transition of (3,3) carbon nanotube supported on patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Bikash C., E-mail: [Virginia Commonwealth University, Department of Physics (United States); Konar, Shyamal [Visva-Bharati, Department of Physics (India); Jena, Puru [Virginia Commonwealth University, Department of Physics (United States)


    Using density functional theory, we systematically investigate the adsorption geometries and electrical properties of (3,3) carbon nanotube (CNT) integrated on hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface. Prior to adsorption of the CNT, the surface is patterned in two different ways by desorbing selective hydrogen atoms from the surface. The (3,3) CNT which is metallic in nature becomes semiconducting with a band gap around the fermi level when it is supported on patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 surface. However, the band gap is reduced when a transverse electric field is applied, allowing the (3,3) CNT on the patterned hydrogen-terminated Si(001):1 Multiplication-Sign 1 to become metallic at a critical field strength. The tuning of electrical properties of the (3,3) CNT integrated with Si surface may have potential technological applications.

  15. SiGe growth on patterned Si(001) substrates : Surface evolution and evidence of modified island coarsening

    NARCIS (Netherlands)

    Zhang, J.J.; Stoffel, M.; Rastelli, A.; Schmidt, O.G.; Jovanovi?, V.; Nanver, L.K.; Bauer, G.


    The morphological evolution of both pits and SiGe islands on patterned Si(001) substrates is investigated. With increasing Si buffer layer thickness the patterned holes transform into multifaceted pits before evolving into inverted truncated pyramids. SiGe island formation and evolution are studied

  16. Structure determination of the Si(001)-(2 x 1)-H reconstruction by surface X-ray diffraction: Weakening of the dimer bond by the addition of hydrogen

    DEFF Research Database (Denmark)

    Lauridsen, E.M.; Baker, J.; Nielsen, M.


    The atomic structure of the monohydride Si(001)-(2 x 1)-H reconstruction has been investigated by surface X-ray diffraction. Atomic relaxations down to the eighth layer have been determined. The bond length of the hydrogenated silicon dimers was found to be 2.47 +/- 0.02 Angstrom. which is longer...... than the dimer bond of the clean (2 x 1)-reconstructed Si(001) surface and also 5% longer than the bulk bond length of 2.35 Angstrom. The differences to the (2 x 1) structure of the clean surface are discussed in terms of the elimination of the weak pi-bond character of the dimer bond by the addition...

  17. Influence of the Localization of Ge Atoms within the Si(001(4 × 2 Surface Layer on Semicore One-Electron States

    Directory of Open Access Journals (Sweden)

    Olha I. Tkachuk


    Full Text Available Adsorption complexes of germanium on the reconstructed Si(001(4 × 2 surface have been simulated by the Si96Ge2Н84 cluster. For Ge atoms located on the surface layer, DFT calculations (B3LYP/6-31G** of their 3d semicore-level energies have shown a clear-cut correlation between the 3d5/2 chemical shifts and mutual arrangement of Ge atoms. Such a shift is positive when only one Ge atom penetrates into the crystalline substrate, while being negative for both penetrating Ge atoms. We interpret these results in terms of the charge distribution in clusters under consideration.

  18. Quasiparticle effects on tunneling currents a study of C2H4 adsorbed on the Si(001)-2x1 surface

    CERN Document Server

    Rignanese, G M; Louie, S G


    We present a first-principles calculation of the quasiparticle electronic structure of ethylene adsorbed on the dimer reconstructed Si(001)-(2 X 1) surface. Within the GW approximation, the self-energy corrections for the adsorbate states are found to be about 1.5 eV larger than those for the states derived from bulk silicon. The calculated quasiparticle band structure is in excellent agreement with photoemission spectra. Finally, the effects of the quasiparticle corrections on the scanning tunneling microscope images of the adsorbed molecules are shown to be important as the lowering of the C2H4 energy levels within GW strongly reduces their tunneling probability.

  19. Ab initio molecular dynamics study of ethylene adsorption onto Si(001) surface: short-time Fourier transform analysis of structural coordinate autocorrelation function. (United States)

    Lee, Yung Ting; Lin, Jyh Shing


    The reaction dynamics of ethylene adsorption onto the Si(001) surface have been studied by combining density functional theory-based molecular dynamics simulations with molecular adsorption sampling scheme for investigating all kinds of reaction pathways and corresponding populations. Based on the calculated results, three possible reaction pathways--the indirect adsorption, the direct adsorption, and the repelling reaction--have been found. First, the indirect adsorption, in which the ethylene (C2H(4(ads))) forms the π-bonded C2H(4(ads)) with the buckled-down Si atom to adsorb on the Si(001) surface and then turns into the di-σ-bonded C2H(4(ads)), is the major reaction pathway. The short-time Fourier transform analysis of structural coordinate autocorrelation function is performed to further investigate the evolution of different vibrational modes along this indirect reaction pathway. This analysis illustrates that the Infrared (IR) inactive peak of the C=C stretching mode of the π-bonded C2 H4(ads) shifts to the IR inactive peak of the C-C stretching mode of di-σ-bonded C2H(4(ads)), which is in a good agreement with the IR inactive peak of the C=C stretching mode vanished in the vibrational spectrum at 150 K (Nagao et al., J. Am. Chem. Soc. 2004, 126, 9922). Second, the direct adsorption, in which the di-σ-bonded C2H(4(ads)) is formed directly with the Si intradimer or the Si interdimer on the Si(001) surface, is the less significant reaction pathway. This reaction pathway leads to the C-C stretching mode and the C-H stretching mode of the di-σ-bonded C2H(4(ads)) appeared in the vibrational spectra at 48 and 150 K, respectively (Nagao et al., J. Am. Chem. Soc. 2004, 126, 9922). Finally, the repelling reaction, in which the C2H(4(g)) first interacts with the Si dimer and then is repelled by Si atoms, is the least important reaction pathway. Consequently, neither the π-bonded C2H(4(ads)) nor the di-σ-bonded C2H(4(ads)) is formed on the Si(001) surface

  20. Structure determination of the indium induced Si(001)-(4X3) reconstruction by surface x-ray diffraction and scanning tunneling microscopy

    DEFF Research Database (Denmark)

    Bunk, O.; Falkenberg, G.; Seehofer, L.


    The indium-induced Si(001)-(4 X 3) reconstruction has been investigated by surface X-ray diffraction (SXRD) measurements with synchrotron radiation and scanning tunneling microscopy (STM). The Patterson function analysis enables us to exclude In dimers as a structural element in this reconstruction....... We present a new structural model which includes 6 In atoms threefold coordinated to Si atoms and 5 displaced Si atoms per unit cell. Relaxations down to the sixth layer were determined. 'Trimers' made up of In-Si-In atoms are a key structural element. (C) 1998 Elsevier Science B.V....

  1. Ordering of vacancies on Si(001)

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.


    Missing dimer vacancies are always present on the clean Si(001) surface. The vacancy density can be increased by ion bombardment (Xe+, Ar+), etching (O2, Br2, I2, etc.) or Ni contamination. The equilibrium shape at low vacancy concentrations (<0.2¿0.3 monolayers) of these vacancy islands is

  2. CMOS-compatible dense arrays of Ge quantum dots on the Si(001 surface: hut cluster nucleation, atomic structure and array life cycle during UHV MBE growth

    Directory of Open Access Journals (Sweden)

    Arapkina Larisa


    Full Text Available Abstract We report a direct observation of Ge hut nucleation on Si(001 during UHV molecular beam epitaxy at 360°C. Nuclei of pyramids and wedges were observed on the wetting layer (WL (M × N patches starting from the coverage of 5.1 Å and found to have different structures. Atomic models of nuclei of both hut species have been built as well as models of the growing clusters. The growth of huts of each species has been demonstrated to follow generic scenarios. The formation of the second atomic layer of a wedge results in rearrangement of its first layer. Its ridge structure does not repeat the nucleus. A pyramid grows without phase transitions. A structure of its vertex copies the nucleus. Transitions between hut species turned out to be impossible. The wedges contain point defects in the upper corners of the triangular faces and have preferential growth directions along the ridges. The derived structure of the {105} facet follows the paired dimer model. Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops. The second generation of huts arises at coverages >10 Å; new huts occupy the whole WL at coverages ~14 Å. Nanocrystalline Ge 2D layer begins forming at coverages >14 Å.

  3. Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by scanning tunneling microscopy, reflected high-energy electron diffraction, and high resolution transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arapkina, L. V.; Krylova, L. A.; Chizh, K. V.; Chapnin, V. A.; Uvarov, O. V.; Yuryev, V. A. [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow 119991 (Russian Federation)


    Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470-650 Degree-Sign C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH{sub 4}F aqueous solutions. It has been shown that smooth surfaces composed of wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures Greater-Than-Or-Equivalent-To 600 Degree-Sign C, whereas clean surfaces obtained at the temperatures <600 Degree-Sign C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.

  4. Chemoselective Reactivity of Bifunctional Cyclooctynes on Si(001)

    CERN Document Server

    Reutzel, Marcel; Lipponer, Marcus A; Länger, Christian; Höfer, Ulrich; Koert, Ulrich; Dürr, Michael


    Controlled organic functionalization of silicon surfaces as integral part of semiconductor technology offers new perspectives for a wide range of applications. The high reactivity of the silicon dangling bonds, however, presents a major hindrance for the first basic reaction step of such a functionalization, i.e., the chemoselective attachment of bifunctional organic molecules on the pristine silicon surface. We overcome this problem by employing cyclooctyne as the major building block of our strategy. Functionalized cyclooctynes are shown to react on Si(001) selectively via the strained cyclooctyne triple bond while leaving the side groups intact. The achieved selectivity originates from the distinctly different adsorption dynamics of the separate functionalities: A direct adsorption pathway is demonstrated for cyclooctyne as opposed to the vast majority of other organic functional groups. The latter ones react on Si(001) via a metastable intermediate which makes them effectively unreactive in competition wi...

  5. SiO mass spectrometry and Si-2p photoemission spectroscopy for the study of oxidation reaction dynamics of Si(001) surface by supersonic O sub 2 molecular beams under 1000K

    CERN Document Server

    Teraoka, Y; Moritani, K


    The Si sup 1 sup 8 O desorption yield was measured in the Si(001) surface temperature region from 900K to 1300K at the sup 1 sup 8 O sub 2 incident energies of 0.7eV, 2.2eV and 3.3eV. The Si sup 1 sup 8 O desorption yield in a surface temperature region higher than 1000K increased with increasing incident energy, indicating the incident-energy-induced oxidation and the variation of angular distribution of Si sup 1 sup 8 O desorption. Inversely, the Si sup 1 sup 8 O desorption yield decreased with increasing incident energy in the region from 900K to 1000K, indicating the coexistence of the passive and the active oxidation. In order to clarify the reaction mechanisms of the later phenomenon, real-time in-situ Si-2p photoemission spectroscopy has been performed. The obtained Si-2p spectra showed the variation of the oxide-nuclei quality from the sub-oxide-rich structure to the SiO sub 2 -rich structure. The formation of the SiO sub 2 structure suppresses the SiO desorption due to the enhanced O sub 2 sticking a...

  6. Spontaneous Pattern Formation on Ion Bombarded Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chason, Eric; Erlebacher, Jonah, Aziz, Michael J.; Floro, Jerrold A.; Sinclair, Michael B.


    Pattern formation on surfaces undergoing low-energy ion bombardment is a common phenomenon. Here, a recently developed in situ spectroscopic light scattering technique was used to monitor periodic ripple evolution on Si(001) during Ar(+) sputtering. Analysis of the rippling kinetics indicated that under high flux sputtering at low temperatures the concentration of mobile species on the surface is saturated, and, surprisingly, is both temperature and ion flux independent. This is due to an effect of ion collision cascades on the concentration of mobile species. This new understanding of surface dynamics during sputtering allowed us to measure straighforwardly the activation energy for atomic migration on the surface to be 1.2+0.1 eV. The technique is generalizable to any material, including high temperature and insulating materials for which surface migration energies are notoriously difficult to measure.

  7. Competing interactions in molecular adsorption: NH(3) on Si(001). (United States)

    Owen, J H G


    Ammonia is a good model system for the study of co-adsorption interactions, including indirect effects such as charge and strain-induced local effects on adsorption sites, and direct interactions such as hydrogen bonding. On the Si(001) surface, it adsorbs molecularly, via a dative bond from the N atom to the down atom of a buckled dimer, and is therefore very sensitive to the local charge conditions. It will then dissociate into -H and -NH(2) groups, adsorbed on the dangling bonds of the Si dimers. The NH(2) groups do not diffuse, so any correlations deriving from interactions during adsorption are preserved, and can be derived by analysis of the arrangements of the NH(2) groups. Hydrogen-bonding interactions are crucial in understanding the behaviour of this system, with significant co-adsorption interactions occurring both along and across rows, outweighing the electrostatic or buckling-related effects. In recent years, there have been several scanning tunnelling microscopy studies and extensive computational modelling of the NH(3) on Si(001) system, attempting to determine a dominant mechanism governing co-adsorption effects. In this review, I will discuss both experimental and theoretical results, make a comparison with similar molecules such as phosphine (PH(3)), and review the different ways in which experimentalists and modellers have approached this complex system.

  8. X-ray standing wave investigations of Group III and V metal adsorption on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Y.; Bedzyk, M.J. [Northwestern Univ., Evanston, IL (United States)]|[Argonne National Lab., IL (United States). Materials Science Div.; Lyman, P.F. [Northwestern Univ., Evanston, IL (United States)


    Investigations of atomic bonding, surface reconstruction, surface dynamics, and growth kinetics of group III and V metals on Si(001) are important for understanding the initial growth stage of III-V semiconductors on Si(001). Such studies can also provide valuable information for other important issues such as surfactant-mediated epitaxy, surface passivation and delta-doping layers. X-ray standing waves generated by dynamical Bragg diffraction were used as an element-specific structural probe for investigating Ga and Sb adsorption on Si(001). These high-resolution measurements reveal important quantitative structural information regarding the dimerized surface structures, and provide a stringent test for structural models proposed by various theoretical calculations. An overview of the X-ray standing wave technique and its application to surface structure and dynamics is presented.

  9. Growth and stability of dysprosium silicide nanostructures on Si(001) (United States)

    Zeman, Matthew; Nemanich, Robert


    The growth and coarsening dynamics of epitaxial dysprosium silicide nanostructures on Si(001) are observed using tunable ultra-violet free electron laser excitation for photo-electron emission microscopy (PEEM). A dense array of compact silicide nanostructures is observed to coarsen during annealing at 950-1050C. Some of the nanostructures grow into large flat-topped rectangular islands at the expense of smaller islands which disappear via Ostwald ripening. The coarsening rate of the island distribution increases with increasing temperature, and the formation of a flat top on the growing islands is related to strain relaxation. Additionally, the shape and growth rates of the islands may be influenced by the island crystal structure and/or local island distributions. A subsequent deposition of dysprosium onto the surface results in the nucleation of new island and nanowire structures. Immediately after the deposition is terminated the nanowires begin to decay from the ends while the larger island structures grow. The decay of the wires can be attributed to Ostwald ripening and is explained in terms of the Gibbs-Thompson relation, where the high adatom concentration at the nanowire ends leads to the diffusion of adatoms away from the wires towards the larger surrounding structures. In situ movies will be presented which detail the growth and coarsening processes.

  10. Optical anisotropy of quasi-1D rare-earth silicide nanostructures on Si(001) (United States)

    Chandola, S.; Speiser, E.; Esser, N.; Appelfeller, S.; Franz, M.; Dähne, M.


    Rare earth metals are known to interact strongly with Si(001) surfaces to form different types of silicide nanostructures. Using STM to structurally characterize Dy and Tb silicide nanostructures on vicinal Si(001), it will be shown that reflectance anisotropy spectroscopy (RAS) can be used as an optical fingerprint technique to clearly distinguish between the formation of a semiconducting two-dimensional wetting layer and the metallic one-dimensional nanowires. Moreover, the distinctive spectral features can be related to structural units of the nanostructures. RAS spectra of Tb and Dy nanostructures are found to show similar features.

  11. The influence of strain on the diffusion of Si dimers on Si(001)

    NARCIS (Netherlands)

    Zoethout, E.; Zoethout, E.; Gurlu, O.; Gürlü, O.; Zandvliet, Henricus J.W.; Poelsema, Bene


    The influence of lattice mismatch-induced tensile strain on the diffusion of Si dimers on Si(001) has been studied. The rate of surface diffusion of a Si dimer along the substrate dimer rows is relatively insensitive to tensile strain, whereas the rate of diffusion for a Si dimer across the

  12. Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Le Breton, J.-C., E-mail:; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P. [Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS-Université de Rennes 1, Campus de Beaulieu, Bât 11 E, 35042 Rennes Cedex (France)


    The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

  13. Growth, morphology, and conductivity in semimetallic/metallic films on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Jnawali, Giriraj


    This dissertation deals with the study of epitaxial growth of semimetallic (Bi) and metallic (Ag) films on Si(001) as well as in situ electrical transport study of those films via surface manipulation. The focus of the transport measurements is to study the influence of the surface morphology or structure on the resistance of the film. In spite of the large lattice mismatch and different lattice geometry, it is possible to grow epitaxial Bi(111) films on Si(001) substrates, which are surprisingly smooth, relaxed and almost free of defects. Due to the two-fold symmetry of the substrates, the Bi(111) film is composed of crystallites rotated by 90 with respect to each other. Annealing of 6 nm film from 150 K to 450 K enables the formation of a periodic interfacial misfit dislocations, which accommodates a remaining lattice mismatch of 2.3 %. The surface/interface roughness and the bulk defect density of the film found to be extremely low, indicating the high crystalline quality of the film with atomically smooth surface and abrupt interface. Similar to the Bi films, Ag grows in a (111) orientation on Si(001) with two 90 rotated domains. The remaining strain of 2.2 % (tensile) is accommodated by the formation of an ordered network of dislocations. The Ag film exhibits atomically smooth surface. Those Bi films and Ag films were used as model systems to study the influence of the surface morphology on the electrical resistance. Surprisingly, all the Bi films (3-170 nm thicknesses) have shown an anomalous behavior of conductance with temperature and thickness. As in the case of doped semiconductor, the conductance increases exponentially from 150 K to 300 K and saturates at 350 K before finally decreasing with temperature. In situ measurements of the resistance during additional Bi deposition on the smooth Bi(111) films exhibit a square root dependent with coverage after a linear increase at very low coverage (1 % of a BL). During additional deposition of Bi, carriers are

  14. Surface functionalization of HF-treated silicon nanowires

    Indian Academy of Sciences (India)


    Nath M and Parkinson B A 2006 Adv. Mater. 18 1865. 21. Chen C L, Chen D R, Jiao X L and Wang C Q 2006. Chem. Commun. 4632. 22. Shao M W, Shan Y Y, Wong N B and Lee S T 2005. Adv. Funct. Mater. 15 1478. 23. Park I, Li Z Y, Pisano A P and Willianms R S 2007. Nano Lett. 10 3106. 24. Shir D, Liu B Z, Mohammad ...

  15. GaN epitaxial layers prepared on nano-patterned Si(001) substrate. (United States)

    Huang, C C; Chang, S J; Kuo, C H; Ko, C H; Wann, Clement H; Cheng, Y C; Lin, W J


    We report the growth of GaN epitaxial layer on Si(001) substrate with nano-patterns prepared by dry etching facility used in integrated circuit (IC) industry. It was found that the GaN epitaxial layer prepared on nano-patterned Si(001) substrate exhibits both cubic and hexagonal phases. It was also found that threading dislocation observed from GaN prepared on nano-patterned Si(001) substrate was significantly smaller than that prepared on conventional unpatterned Si(111) substrate. Furthermore, it was found that we can reduce the tensile stress in GaN epitaxial layer by about 78% using the nano-patterned Si(001) substrate.

  16. Formation of pyramid-like nanostructures in MBE-grown Si films on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Galiana, N.; Martin, P.P.; Rodriguez-Canas, E.; Esteban-Betegon, F.; Alonso, M.; Ruiz, A. [CSIC, Instituto de Ciencia de Materiales de Madrid, Madrid (Spain); Garzon, L.; Ocal, C. [CSIC, Institut de Ciencia de Materials de Barcelona, Barcelona (Spain); Munuera, C. [CSIC, Instituto de Ciencia de Materiales de Madrid, Madrid (Spain); CSIC, Institut de Ciencia de Materials de Barcelona, Barcelona (Spain); Varela, M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)


    The growth of Si homoepitaxial layers on Si(001) substrates by molecular beam epitaxy is analyzed for a set of growth conditions in which diverse nanometer-scale features develop. Using Si substrates prepared by exposure to HF vapor and annealing in ultra-high vacuum, a rich variety of surface morphologies is found for different deposited layer thicknesses and substrate temperatures in a reproducible way, showing a critical dependence on both. Arrays of 3D islands (truncated pyramids), percolated ridge networks, and square pit (inverted pyramid) distributions are observed. We analyze the obtained arrangements and find remarkable similarities to other semiconductor though heteroepitaxial systems. The nanoscale entities (islands or pits) display certain self assembly and ordering, concerning size, shape, and spacing. Film growth sequence follows the 'islands-coalescence-2D growth' pathway, eventually leading to optimum flat morphologies for high enough thickness and temperature. (orig.)

  17. Electrical isolation of dislocations in Ge layers on Si(001 substrates through CMOS-compatible suspended structures

    Directory of Open Access Journals (Sweden)

    Vishal Ajit Shah, Maksym Myronov, Chalermwat Wongwanitwatana, Lewis Bawden, Martin J Prest, James S Richardson-Bullock, Stephen Rhead, Evan H C Parker, Terrance E Whall and David R Leadley


    Full Text Available Suspended crystalline Ge semiconductor structures are created on a Si(001 substrate by a combination of epitaxial growth and simple patterning from the front surface using anisotropic underetching. Geometric definition of the surface Ge layer gives access to a range of crystalline planes that have different etch resistance. The structures are aligned to avoid etch-resistive planes in making the suspended regions and to take advantage of these planes to retain the underlying Si to support the structures. The technique is demonstrated by forming suspended microwires, spiderwebs and van der Pauw cross structures. We finally report on the low-temperature electrical isolation of the undoped Ge layers. This novel isolation method increases the Ge resistivity to 280 Ω cm at 10 K, over two orders of magnitude above that of a bulk Ge on Si(001 layer, by removing material containing the underlying misfit dislocation network that otherwise provides the main source of electrical conduction.

  18. Site-Specific Reactivity of Ethylene at Distorted Dangling-Bond Configurations on Si(001). (United States)

    Pecher, Josua; Mette, Gerson; Dürr, Michael; Tonner, Ralf


    Differences in adsorption and reaction energetics for ethylene on Si(001) are reported with respect to distorted dangling-bond configurations induced by hydrogen precoverage, as obtained by DFT calculations. This can help to understand the influence of surface defects and precoverage on the reactivity of organic molecules on semiconductor surfaces in general. The results show that the reactivity of surface dimers fully enclosed by hydrogen-covered atoms is essentially unchanged compared to the clean surface. This is confirmed by scanning tunneling microscopy measurements. On the contrary, adsorption sites with partially covered surface dimers show a drastic increase in reactivity. This is due to a lowering of the reaction barrier by more than 50 % relative to the clean surface, which is in line with previous experiments. Adsorption on dimers enclosed by molecule (ethylene)-covered surface atoms is reported to have a strongly decreased reactivity, as a result of destabilization of the intermediate state due to steric repulsion; this is quantified through periodic energy decomposition analysis. Furthermore, an approach for the calculation of Gibbs energies of adsorption based on statistical thermodynamics considerations is applied to the system. The results show that the loss in molecular entropy leads to a significant destabilization of adsorption states. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Flat epitaxial ferromagnetic CoFe{sub 2}O{sub 4} films on buffered Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Bachelet, R. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, 08193 Bellaterra, Barcelona (Spain); Coux, P. de [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, 08193 Bellaterra, Barcelona (Spain); CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4 (France); Warot-Fonrose, B. [CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4 (France); Skumryev, V. [Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain, and Dep. de Fisica, Univ. Autonoma de Barcelona, 08193 Bellaterra (Spain); Fontcuberta, J. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, 08193 Bellaterra, Barcelona (Spain); Sanchez, F., E-mail: [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, 08193 Bellaterra, Barcelona (Spain)


    Ferromagnetic films of spinel CoFe{sub 2}O{sub 4} have been grown epitaxially on Si(001) using CeO{sub 2}/YSZ double buffer layers. The heterostructures were built in a single process by pulsed laser deposition with real-time control by reflection high-energy electron diffraction. YSZ and CeO{sub 2} grow cube-on-cube on Si(001) and CoFe{sub 2}O{sub 4} grows with (111) out-of-plane orientation, presenting four in-plane crystal domains. The interface with the buffer layers is smooth and the CoFe{sub 2}O{sub 4} surface is atomically flat, with roughness below 0.3 nm. The films are ferromagnetic with saturation magnetization around 300 emu/cm{sup 3}. The properties signal that CoFe{sub 2}O{sub 4} is a good candidate for monolithic devices based on ferromagnetic insulating spinels.

  20. Dimer rotation on the carbon-induced Si(001)-c(4×4) structure (United States)

    Peng, G. W.; Sun, Y. Y.; Huan, A. C. H.; Feng, Y. P.


    We present first-principles results identifying the reaction pathways for Si dimer rotations on the carbon-induced Si(001)-c(4×4) surface. The nudged elastic band calculations show that the recently proposed rotated dimer model [Phys. Rev. Lett. 94, 076102 (2005)] can be obtained from the refined missing dimer model by dimer rotation with small energy barriers. It is found that the energy barrier is sensitive to the rotation directions of Si dimers. The energy barrier along the minimum energy path (MEP) is 0.82eV . Three stable configurations are identified along the MEP, one of which with a single rotated dimer is more stable than all existing models and its energy is lower than that of the rotated dimer model, the previously most stable structure, by 0.25eV per c(4×4) cell. The stabilization mechanism of the new stable structure is analyzed. We propose a possible method to search for new stable structures based on the existing models by mapping out the reaction paths in the phase configuration.

  1. Polarized Raman spectroscopy study of NiSi film grown on Si(001) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Li; Ren, Yiming; Tang, Bo; Cheng, Xinhong; Zhang, Xuefei; Xu, Dapeng; Luo, Hijun; Huang, Yunmi [Wenzhou University, Department of Physics, Wenzhou (China)


    We report on the growth of NiSi film on Si(001) substrate with an orientation of NiSi[200]//Si[001]. Polarized Raman spectroscopy was used to assign the symmetry of the NiSi Raman peaks. Raman peaks at 213 cm{sup -1}, 295 cm{sup -1}, and 367 cm{sup -1} are assigned to be A{sub g} symmetry and peaks at 196 cm{sup -1}, and 254 cm{sup -1} are B{sub 3g} symmetry. (orig.)

  2. Strain in nanoscale Germanium hut clusters on Si(001) studied by x-ray diffraction

    DEFF Research Database (Denmark)

    Steinfort, A.J.; Scholte, P.M.L.O.; Ettema, A.


    Scanning tunneling microscopy and synchrotron x-ray diffraction have been used to investigate nanoscale Ge hut clusters on Si(001). We have been able to identify the contributions to the scattered x-ray intensity which arise solely from the hut clusters and have shown that x-ray diffraction can b...

  3. Ab initio density functional theory study on the atomic and electronic structure of GaP/Si(001) heterointerfaces (United States)

    Romanyuk, O.; Supplie, O.; Susi, T.; May, M. M.; Hannappel, T.


    The atomic and electronic band structures of GaP/Si(001) heterointerfaces were investigated by ab initio density functional theory calculations. Relative total energies of abrupt interfaces and mixed interfaces with Si substitutional sites within a few GaP layers were derived. It was found that Si diffusion into GaP layers above the first interface layer is energetically unfavorable. An interface with Si/Ga substitution sites in the first layer above the Si substrate is energetically the most stable one in thermodynamic equilibrium. The electronic band structure of the epitaxial GaP/Si(001) heterostructure terminated by the (2 ×2 ) surface reconstruction consists of surface and interface electronic states in the common band gap of two semiconductors. The dispersion of the states is anisotropic and differs for the abrupt Si-Ga, Si-P, and mixed interfaces. Ga 2 p , P 2 p , and Si 2 p core-level binding-energy shifts were computed for the abrupt and the lowest-energy heterointerface structures. Negative and positive core-level shifts due to heterovalent bonds at the interface are predicted for the abrupt Si-Ga and Si-P interfaces, respectively. The distinct features in the heterointerface electronic structure and in the core-level shifts open new perspectives in the experimental characterization of buried polar-on-nonpolar semiconductor heterointerfaces.

  4. In situ study of the endotaxial growth of hexagonal CoSi{sub 2} nanoplatelets in Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Silva Costa, Daniel da; Kellermann, Guinther, E-mail: [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná 81531-990 (Brazil); Huck-Iriart, Cristián; Giovanetti, Lisandro J.; Requejo, Félix G. [Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, CONICET, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata), CC/16 suc. 4, 1900 La Plata (Argentina); Craievich, Aldo F. [Instituto de Física, Universidade de São Paulo, CP 66318, CEP 05315-970, São Paulo (Brazil)


    This investigation aims at studying–by in situ grazing-incidence small-angle x-ray scattering–the process of growth of hexagonal CoSi{sub 2} nanoplatelets endotaxially buried in a Si(001) wafer. The early formation of spherical Co nanoparticles with bimodal size distribution in the deposited silica thin film during a pretreatment at 500 °C and their subsequent growth at 700 °C were also characterized. Isothermal annealing at 700 °C promotes a drastic reduction in the number of the smallest Co nanoparticles and a continuous decrease in their volume fraction in the silica thin film. At the same time, Co atoms diffuse across the SiO{sub 2}/Si(001) interface into the silicon wafer, react with Si, and build up thin hexagonal CoSi{sub 2} nanoplatelets, all of them with their main surfaces parallel to Si(111) crystallographic planes. The observed progressive growths in thickness and lateral size of the hexagonal CoSi{sub 2} nanoplatelets occur at the expense of the dissolution of the small Co nanoparticles that are formed during the pretreatment at 500 °C and become unstable at the annealing temperature (700 °C). The kinetics of growth of the volume fraction of hexagonal platelets is well described by the classical Avrami equation.

  5. Spin polarization and magnetic characteristics at C6H6/Co2MnSi(001) spinterface (United States)

    Sun, Meifang; Wang, Xiaocha; Mi, Wenbo


    Organic materials with mechanical flexibility, low cost, chemical engineering, and long spin lifetime attract considerable attention for building spintronic devices. Here, a C6H6/Co2MnSi(001) spinterface is investigated by first-principles calculations and spin-polarized scanning tunneling microscopy simulations. Several high symmetry adsorption sites are discussed, together with two possible surface terminations of Co2MnSi(001). An inversion of the spin polarization is induced near EF even in the case of an external electric field, indicating that C6H6 can act as a spin filter to exploit the spin injection efficiency in organic spintronic devices. Unlike previous studies on molecule/ferromagnet interfaces, this inversion is closely related to the electronic structure of the atoms in the subsurface layer of Co2MnSi according to the orbital symmetry analysis. Furthermore, the magnetic moment and magnetic anisotropic energy (MAE) in the outermost Co2MnSi layer are studied. Particularly, in the most stable configuration, the sign of MAE is inversed due to hybridization between C p and Co d z 2 orbitals, which suggests that a greater modification on MAE can be achieved by the use of a highly chemically reactive organic molecule. These findings improve the study on the engineering of magnetic properties at molecule/ferromagnetic interfaces through a single π-conjugated organic molecule.

  6. Molecular beam epitaxial growth of BaTiO3 single crystal on Ge-on-Si(001) substrates (United States)

    Merckling, C.; Saint-Girons, G.; Botella, C.; Hollinger, G.; Heyns, M.; Dekoster, J.; Caymax, M.


    Thin films of perovskite type BaTiO3 (BTO) oxide have been grown epitaxially directly on Ge(001) surface at high temperature using molecular beam epitaxy. A stable (2×1) BaGex surface periodicity is the critical enabling template for subsequent BTO heteroepitaxy on Ge(001). Reflection high energy electron diffraction (RHEED) and transmission electron microscopy indicate that high quality heteroepitaxy on Ge-on-Si(001) take place with ⟨100⟩BTO(001)∥⟨110⟩Ge(001) confirming a 45° rotation epitaxial relationship. X-ray diffraction has been used to study the BTO lattice parameters and we evidenced that both tetragonal and cubic phases of BTO are present in the epilayer.

  7. Real-time observation of initial stage on Si(001) oxidation studied by O-1s photoemission spectroscopy using synchrotron radiation

    CERN Document Server

    Yoshigoe, A; Teraoka, Y


    The real-time photoemission measurements of the initial thermal oxidation on the Si(001) surface with O sub 2 gas (1 x 10 sup - sup 4 Pa) at the surface temperatures of 860, 895, 945 and 1000 K have been performed by using synchrotron radiation. In order to study the oxide-layer growth mode depending on the surface temperature, the time evolution of integrated peak area intensity of O-1s photoemission spectra was analyzed on the basis of the Langmuir-type and the auto-catalytic reaction kinetics models. It was found that the oxidation at 860, 895 and 945 K has progressed with the Langmuir-type adsorption. On the other hand, the oxidation at 1000 K has shown the characteristic of the auto-catalytic growth. We have succeeded in analyzing the reaction kinetics of thermal Si(001) oxidation by using the real-time in-situ O-1s photoemission measurements. (author)

  8. Optimal Growth Conditions for Selective Ge Islands Positioning on Pit-Patterned Si(001

    Directory of Open Access Journals (Sweden)

    Bergamaschini R


    Full Text Available Abstract We investigate ordered nucleation of Ge islands on pit-patterned Si(001 using an original hybrid Kinetic Monte Carlo model. The method allows us to explore long time-scale evolution while using large simulation cells. We analyze the possibility to achieve selective nucleation and island homogeneity as a function of the various parameters (flux, temperature, pit period able to influence the growth process. The presence of an optimal condition where the atomic diffusivity is sufficient to guarantee nucleation only within pits, but not so large to induce significant Ostwald ripening, is clearly demonstrated.

  9. Disentangling phonon and impurity interactions in δ-doped Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Mazzola, Federico; Wells, Justin W., E-mail: [Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim (Norway); Polley, Craig M. [MAX IV Laboratory, Lund University, 221 00 Lund (Sweden); School of Physics, Centre of Excellence for Quantum Computation and Communication Technology, University of New South Wales, Sydney, NSW 2052 (Australia); Miwa, Jill A. [Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, 8000 Aarhus C (Denmark); Simmons, Michelle Y. [School of Physics, Centre of Excellence for Quantum Computation and Communication Technology, University of New South Wales, Sydney, NSW 2052 (Australia)


    We present a study of the phonon and impurity interactions in a shallow two dimensional electron gas formed in Si(001). A highly conductive ultra-narrow n-type dopant δ-layer, which serves as a platform for quantum computation architecture, is formed and studied by angle resolved photoemission spectroscopy (ARPES) and temperature dependent nanoscale 4-point probe (4PP). The bandstructure of the δ-layer state is both measured and simulated. At 100 K, good agreement is only achieved by including interactions; electron-impurity scattering (W{sub 0} = 56 to 61 meV); and electron-phonon coupling (λ = 0.14 ± 0.04). These results are shown to be consistent with temperature dependent 4PP resistance measurements which indicate that at 100 K, ≈7∕8 of the measured resistance is due to impurity scattering with the remaining 1/8 coming from phonon interactions. In both resistance and bandstructure measurements, the impurity contribution exhibits a variability of ≈9% for nominally identical samples. The combination of ARPES and 4PP affords a thorough insight into the relevant contributions to electrical resistance in reduced dimensionality electronic platforms.

  10. Recipes for the fabrication of strictly ordered Ge islands on pit-patterned Si(001) substrates. (United States)

    Grydlik, Martyna; Langer, Gregor; Fromherz, Thomas; Schäffler, Friedrich; Brehm, Moritz


    We identify the most important parameters for the growth of ordered SiGe islands on pit-patterned Si(001) substrates. From a multi-dimensional parameter space we link individual contributions to isolate their influence on ordered island growth. This includes the influences of: the pit size, pit depth and pit period on the Si buffer layer and subsequent Ge growth; the pit sidewall inclination on Ge island growth; the amount of Ge on island morphologies as well as the influences of the pit-size homogeneity, the pit period, the Ge growth temperature and rate on island formation. We highlight that the initial pit shape and pit size in combination with the growth conditions of the Si buffer layer should be adjusted to provide suitable preconditions for the growth of Ge islands with the desired size, composition and nucleation position. Furthermore, we demonstrate that the wetting layer between pits can play the role of a stabilizer that inhibits shape transformations of ordered islands. Thus, dislocation formation within islands can be delayed, uniform arrays of one island type can be fabricated and secondary island nucleation between pits can be impeded. These findings allow us to fabricate perfectly ordered and homogeneous Ge islands on one and the same sample, even if the pit period is varied from a few hundred nanometres to several micrometres.

  11. Cubic Gallium Nitride on Micropatterned Si (001) for Longer Wavelength LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Durniak, Mark T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Science and Engineering; Chaudhuri, Anabil [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Smith, Michael L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Allerman, Andrew A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Lee, S. C. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Brueck, S. R. J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Wetzel, Christian [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics, Applied Physics, and Astronomy and Dept. of Materials Science and Engineering


    GaInN/GaN heterostructures of cubic phase have the potential to overcome the limitations of wurtzite structures commonly used for light emitting and laser diodes. Wurtzite GaInN suffers from large internal polarization fields, which force design compromises ( 0001 ) towards ultra-narrow quantum wells and reduce recombination volume and efficiency. Cubic GaInN microstripes grown at Rensselaer Polytechnic Institute by metal organic vapor phase epitaxy on micropatterned Si , with {111} v-grooves oriented along Si ( 001 ) , offer a system free of internal polarization fields, wider quantum wells, and smaller <00$\\bar1$> bandgap energy. We prepared 6 and 9 nm Ga x In 1-x N/GaN single quantum well structures with peak wavelength ranges from 520 to 570 nm with photons predominately polarized perpendicular to the grooves. We estimate a cubic InN composition range of 0 < x < 0.5 and an upper limit of the internal quantum efficiency of 50%. Stripe geometry and polarization may be suitable for mode confinement and reduced threshold stimulated emission.

  12. Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001). (United States)

    Scigaj, Mateusz; Dix, Nico; Gázquez, Jaume; Varela, María; Fina, Ignasi; Domingo, Neus; Herranz, Gervasi; Skumryev, Vassil; Fontcuberta, Josep; Sánchez, Florencio


    The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature.

  13. Spot profile analysis and lifetime mapping in ultrafast electron diffraction: Lattice excitation of self-organized Ge nanostructures on Si(001

    Directory of Open Access Journals (Sweden)

    T. Frigge


    Full Text Available Ultrafast high energy electron diffraction in reflection geometry is employed to study the structural dynamics of self-organized Germanium hut-, dome-, and relaxed clusters on Si(001 upon femtosecond laser excitation. Utilizing the difference in size and strain state the response of hut- and dome clusters can be distinguished by a transient spot profile analysis. Surface diffraction from {105}-type facets provide exclusive information on hut clusters. A pixel-by-pixel analysis of the dynamics of the entire diffraction pattern gives time constants of 40, 160, and 390 ps, which are assigned to the cooling time constants for hut-, dome-, and relaxed clusters.

  14. Defects at the Si(001 )/a -SiO2 interface: Analysis of structures generated with classical force fields and density functional theory (United States)

    Mehes, E.; Patterson, C. H.


    Defects at the Si(001 )/a -SiO2 interface were simulated using a combination of classical force field molecular dynamics and first-principles total-energy minimization techniques. The second generation charge-optimized many-body potential COMB10 was used to generate a -SiO2 which was placed on an ideally terminated Si(001) surface and briefly annealed before being relaxed using density functional theory. Si dimers form at the Si interface on relaxation unless the Si surface has been oxidized. Pb 1 defects form when Si dimers do not bond to O atoms in the a -SiO2 layer. Mismatch in Si atom pairings at the dimerized surface leads to Si2O ≡Si . defects at the interface which may be the structure of a defect denoted S in electron-spin resonance (ESR) studies. Relatively few Pb 0 defects with a magnetic moment form at the Si interface. a -SiO2 generated by heating and quenching a system with periodic boundary conditions is free of E' defects. Afterward, this structure is placed on the Si surface and allowed to relax. The main type of E' defect which forms is a forward oriented Eα' defect. ESR hyperfine parameters for each defect category are calculated and compared to experimental data. Defect densities of states are calculated and compared to experiment.

  15. Ge/Si(001) heterostructures with dense arrays of Ge quantum dots: morphology, defects, photo-emf spectra and terahertz conductivity. (United States)

    Yuryev, Vladimir A; Arapkina, Larisa V; Storozhevykh, Mikhail S; Chapnin, Valery A; Chizh, Kirill V; Uvarov, Oleg V; Kalinushkin, Victor P; Zhukova, Elena S; Prokhorov, Anatoly S; Spektor, Igor E; Gorshunov, Boris P


    : Issues of Ge hut cluster array formation and growth at low temperatures on the Ge/Si(001) wetting layer are discussed on the basis of explorations performed by high resolution STM and in-situ RHEED. Dynamics of the RHEED patterns in the process of Ge hut array formation is investigated at low and high temperatures of Ge deposition. Different dynamics of RHEED patterns during the deposition of Ge atoms in different growth modes is observed, which reflects the difference in adatom mobility and their 'condensation' fluxes from Ge 2D gas on the surface for different modes, which in turn control the nucleation rates and densities of Ge clusters. Data of HRTEM studies of multilayer Ge/Si heterostructures are presented with the focus on low-temperature formation of perfect films.Heteroepitaxial Si p-i-n-diodes with multilayer stacks of Ge/Si(001) quantum dot dense arrays built in intrinsic domains have been investigated and found to exhibit the photo-emf in a wide spectral range from 0.8 to 5 μm. An effect of wide-band irradiation by infrared light on the photo-emf spectra has been observed. Photo-emf in different spectral ranges has been found to be differently affected by the wide-band irradiation. A significant increase in photo-emf is observed in the fundamental absorption range under the wide-band irradiation. The observed phenomena are explained in terms of positive and neutral charge states of the quantum dot layers and the Coulomb potential of the quantum dot ensemble. A new design of quantum dot infrared photodetectors is proposed.By using a coherent source spectrometer, first measurements of terahertz dynamical conductivity (absorptivity) spectra of Ge/Si(001) heterostructures were performed at frequencies ranged from 0.3 to 1.2 THz in the temperature interval from 300 to 5 K. The effective dynamical conductivity of the heterostructures with Ge quantum dots has been discovered to be significantly higher than that of the structure with the same amount of bulk

  16. On the compliant behaviour of free-standing Si nanostructures on Si(001) for Ge nanoheteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kozlowski, Grzegorz


    phenomenon was observed. In clear contradiction to the present NHE theory, no strain partitioning phenomenon was found even for {approx}50 nm wide Si pillars for which the compliant substrate effects are expected. The absence of the strain partitioning between Ge and Si is caused by the stress field exerted by the SiO{sub 2} growth mask on the Si nanopillar. In contrast to such nanostructures monolithically prepared from a Si(001) wafer, first results in this thesis clearly prove the strain partitioning phenomenon within Ge/Si nanostructures on Silicon-on-insulator substrate. Here, the compliant substrate effects were clearly observed for pillar widths even bigger than 50 nm. This experimental work demonstrates, that NHE with its compliant substrate effects, offers an interesting approach for high quality Ge nanostructures on Si, avoiding even the misfit dislocation network with its non-tolerable electrical activity in Ge nanodevices. However, the theory does not yet include important aspects of thin film growth on the nano-scale and must be further developed. It is the aim of this PhD thesis to provide this experimental basis for the Ge/Si heterosystem. Finally, it is noted that here developed growth approach is fully Si CMOS compatible and is not only relevant for Ge integration but also for other lattice mismatched alternative semiconductors (GaAs etc.) to enable higher performance / new functions in future Si microelectronics technologies.

  17. Monolithically integrated InGaAs/GaAs/AlGaAs quantum well laser grown by MOCVD on exact Ge/Si(001) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Aleshkin, V. Ya.; Dubinov, A. A.; Krasilnik, Z. F.; Kudryavtsev, K. E.; Novikov, A. V.; Yurasov, D. V., E-mail: [Institute for Physics of Microstructures of the Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Baidus, N. V.; Samartsev, I. V. [Physical-Technical Research Institute of Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Fefelov, A. G. [FGUE “Salut,” 603950 Nizhny Novgorod (Russian Federation); Nekorkin, S. M. [Institute for Physics of Microstructures of the Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); Physical-Technical Research Institute of Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Pavlov, D. A.; Sushkov, A. A. [Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Skorokhodov, E. V.; Shaleev, M. V.; Yablonskiy, A. N.; Yunin, P. A. [Institute for Physics of Microstructures of the Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation)


    We report on realization of the InGaAs/GaAs/AlGaAs quantum well laser grown by metallorganic chemical vapor deposition on a virtual Ge-on-Si(001) substrate. The Ge buffer layer has been grown on a nominal Si(001) substrate by solid-source molecular beam epitaxy. Such Ge buffer possessed rather good crystalline quality and smooth surface and so provided the subsequent growth of the high-quality A{sub 3}B{sub 5} laser structure. The laser operation has been demonstrated under electrical pumping at 77 K in the continuous wave mode and at room temperature in the pulsed mode. The emission wavelengths of 941 nm and 992 nm have been obtained at 77 K and 300 K, respectively. The corresponding threshold current densities were estimated as 463 A/cm{sup 2} at 77 K and 5.5 kA/cm{sup 2} at 300 K.

  18. Tailoring Lattice Strain and Ferroelectric Polarization of Epitaxial BaTiO3Thin Films on Si(001). (United States)

    Lyu, Jike; Fina, Ignasi; Solanas, Raul; Fontcuberta, Josep; Sánchez, Florencio


    Ferroelectric BaTiO 3 films with large polarization have been integrated with Si(001) by pulsed laser deposition. High quality c-oriented epitaxial films are obtained in a substrate temperature range of about 300 °C wide. The deposition temperature critically affects the growth kinetics and thermodynamics balance, resulting on a high impact in the strain of the BaTiO 3 polar axis, which can exceed 2% in films thicker than 100 nm. The ferroelectric polarization scales with the strain and therefore deposition temperature can be used as an efficient tool to tailor ferroelectric polarization. The developed strategy overcomes the main limitations of the conventional strain engineering methodologies based on substrate selection: it can be applied to films on specific substrates including Si(001) and perovskites, and it is not restricted to ultrathin films.

  19. Enhanced optical second-harmonic generation from the current-biased graphene/SiO2/Si(001) structure. (United States)

    An, Yong Q; Nelson, Florence; Lee, Ji Ung; Diebold, Alain C


    We find that optical second-harmonic generation (SHG) in reflection from a chemical-vapor-deposition graphene monolayer transferred onto a SiO2/Si(001) substrate is enhanced about 3 times by the flow of direct current electric current in graphene. Measurements of rotational-anisotropy SHG revealed that the current-induced SHG from the current-biased graphene/SiO2/Si(001) structure undergoes a phase inversion as the measurement location on graphene is shifted laterally along the current flow direction. The enhancement is due to current-associated charge trapping at the graphene/SiO2 interface, which introduces a vertical electric field across the SiO2/Si interface that produces electric field-induced SHG. The phase inversion is due to the positive-to-negative polarity switch in the current direction of the trapped charges at the current-biased graphene/SiO2 interface.

  20. In situ photoemission spectroscopy for chemical reaction dynamics study of Si (001) oxidation by using high-energy-resolution synchrotron radiation

    CERN Document Server

    Teraoka, Y


    The translation kinetic energy of incident molecules is an important parameter for the study of surface chemical reaction mechanisms. New adsorption reactions, which have been induced by the O sub 2 translational kinetic energy up to 3 eV, have been found in the O sub 2 Si(001) system by applying surface-sensitive photoemission spectroscopy with supersonic molecular beam techniques and high-energy-resolution synchrotron radiation. The termination of dangling bonds of the topmost Si-dimers strongly affected the oxidation of their backbonds. By controlling the translational kinetic energy of incident O sub 2 molecules, the formation of oxide layers at a sub-nanometer scale is possible at room temperature. (author)

  1. Nonlinear Amplitude Evolution During Spontaneous Patterning of Ion-Bombarded Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chason, Eric; Erlebacher, Jonah, Aziz, Michael J.; Floro, Jerold A.; Sinclair, Michael B.


    The time evolution of the amplitude of periodic nanoscale ripple patterns formed on Ar+ sputtered Si(OOl ) surfaces was examined using a recently developed in situ spectroscopic technique. At sufficiently long times, we find that the amplitude does not continue to grow exponentially as predicted by the standard Bradley-Harper sputter rippling model. In accounting for this discrepancy, we rule out effects related to the concentration of mobile species, high surface curvature, surface energy anisotropy, and ion-surface interactions. We observe that for all wavelengths the amplitude ceases to grow when the width of the topmost terrace of the ripples is reduced to approximately 25 nm. This observation suggests that a short circuit relaxation mechanism limits amplitude . growth. A strategy for influencing the ultimate ripple amplitude is discussed.

  2. First-principles calculation of mechanical properties of Si <001> nanowires and comparison to nanomechanical theory

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B; Rudd, R E


    We report the results of first-principles density functional theory calculations of the Young's modulus and other mechanical properties of hydrogen-passivated Si {l_angle}001{r_angle} nanowires. The nanowires are taken to have predominantly {l_brace}100{r_brace}surfaces, with small {l_brace}110{r_brace} facets according to the Wulff shape. The Young's modulus, the equilibrium length and the constrained residual stress of a series of prismatic beams of differing sizes are found to have size dependences that scale like the surface area to volume ratio for all but the smallest beam. The results are compared with a continuum model and the results of classical atomistic calculations based on an empirical potential. We attribute the size dependence to specific physical structures and interactions. In particular, the hydrogen interactions on the surface and the charge density variations within the beam are quantified and used both to parameterize the continuum model and to account for the discrepancies between the two models and the first-principles results.

  3. Single-photon emission from electrically driven InP quantum dots epitaxially grown on CMOS-compatible Si(001). (United States)

    Wiesner, M; Schulz, W-M; Kessler, C; Reischle, M; Metzner, S; Bertram, F; Christen, J; Roßbach, R; Jetter, M; Michler, P


    The heteroepitaxy of III-V semiconductors on silicon is a promising approach for making silicon a photonic platform. Mismatches in material properties, however, present a major challenge, leading to high defect densities in the epitaxial layers and adversely affecting radiative recombination processes. However, nanostructures, such as quantum dots, have been found to grow defect-free even in a suboptimal environment. Here we present the first realization of indium phosphide quantum dots on exactly oriented Si(001), grown by metal-organic vapour-phase epitaxy. We report electrically driven single-photon emission in the red spectral region, meeting the wavelength range of silicon avalanche photodiodes' highest detection efficiency.

  4. Room temperature photoluminescence (lambda = 1.3 mu m) of InGaAs quantum dots in Si(001) substrate

    CERN Document Server

    Burbaev, T M; Kurbatov, V A; Rzaev, M M; Tsvetkov, V A; Tsekhosh, V I


    A heterostructure with GaAs/In sub x Ga sub 1 sub - sub x As quantum dots has exhibit intense photoluminescence in the range of 1.3 mu m at room temperature. It was grown on Si(001) substrate with Si sub 1 sub - sub x Ge sub x buffer layer. The growth process was performed consecutively in two molecular beam epitaxy systems with over loading through out the atmosphere. Results of growth process study by the fast electron diffraction method are presented

  5. Molecular beam epitaxy of SrTiO3 on Si (001): Early stages of the growth and strain relaxation (United States)

    Niu, G.; Saint-Girons, G.; Vilquin, B.; Delhaye, G.; Maurice, J.-L.; Botella, C.; Robach, Y.; Hollinger, G.


    The molecular beam epitaxy of SrTiO3 (STO) layers on Si (001) is studied, focusing on the early stages of the growth and on the strain relaxation process. Evidence is given that even for optimized growth conditions, STO grows initially amorphous on silicon and recrystallizes, leading to the formation of an atomically abrupt heterointerface with silicon. Just after recrystallization, STO is partially strained. Further increase in its thickness leads to the onset of a progressive plastic relaxation mechanism. STO recovers its bulk lattice parameter for thicknesses of the order of 30 ML.

  6. Kirkendall void formation in reverse step graded Si1‑xGex/Ge/Si(001) virtual substrates (United States)

    Sivadasan, Vineet; Rhead, Stephen; Leadley, David; Myronov, Maksym


    Formation of Kirkendall voids is demonstrated in the Ge underlayer of reverse step graded Si1‑xGex/Ge buffer layers grown on Si(001) using reduced pressure chemical vapour deposition (RP-CVD). This phenomenon is seen when the constant composition Si1‑xGex layer is grown at high temperatures and for x ≤ 0.7. The density and size of the spherical voids can be tuned by changing Ge content in the Si1‑xGex and other growth parameters.

  7. Spectroscopic phonon and extended x-ray absorption fine structure measurements on 3C-SiC/Si (001) epifilms (United States)

    Talwar, Devki N.; Wan, Linyu; Tin, Chin-Che; Lin, Hao-Hsiung; Feng, Zhe Chuan


    Comprehensive experimental and theoretical studies are reported to assess the vibrational and structural properties of 3C-SiC/Si (001) epilayers grown by chemical vapor deposition in a vertical reactor configuration. While the phonon features are evaluated using high resolution infrared reflectance (IRR) and Raman scattering spectroscopy (RSS) - the local inter-atomic structure is appraised by synchrotron radiation extended x-ray absorption fine structure (SR-EXAFS) method. Unlike others, our RSS results in the near backscattering geometry revealed markedly indistinctive longitudinal- and transverse-optical phonons in 3C-SiC epifilms of thickness d theory is utilized to explain the observed atypical IRR spectra in 3C-SiC/Si (001) epifilms. High density intrinsic defects present in films and/or epilayer/substrate interface are likely to be responsible for (a) releasing misfit stress/strains, (b) triggering atypical features in IRR spectra, and (c) affecting observed local structural traits in SR-EXAFS.

  8. Tilt boundary formation in GeSi/Si (001 vicinal heterosystem

    Directory of Open Access Journals (Sweden)

    Aleksei V. Kolesnikov


    Full Text Available The structural state of GexSi1-x films grown on Si substrates with the vicinal orientation (1 1 13 has been studied. The (1 1 13 orientation has been obtained by rotating the singular plane (001 around the [1 1 ¯0] axis. The x parameter of GexSi1-x films in different samples ranged from 0.083 to 0.268. Triclinic distortions arising in film crystal lattice have been analyzed using our technique developed for the determination of epitaxial layer structural parameters based on the X-ray diffractometry data. It has been established that during the epitaxial process the film lattice turns around the direction of surface steps due to the introduction of misfit dislocations into the interface. Dislocations with Burgers vector a/2〈110〉 which is not parallel to the interface create an analog of a tilt boundary. The turning angle value ψ is proportional to the misfit dislocation density. This phenomenon is associated with a decrease of the interface symmetry that leads to a change in the efficiency of stress relieving by dislocations belonging to different families. The influence of these families on the low-angle boundary formation is considered. Experimental values of the ψ angle and shear strain for the [13 13 2¯] and [1¯ 1 0] directions lying in the interface (1 1 13 have been defined. A comparison of the experimental and calculated values of ψ for the [13 13 2¯] direction is provided.

  9. Cubic GaN epilayers grown by molecular beam epitaxy on thin β-SiC/Si (001) substrates (United States)

    As, D. J.; Frey, T.; Schikora, D.; Lischka, K.; Cimalla, V.; Pezoldt, J.; Goldhahn, R.; Kaiser, S.; Gebhardt, W.


    The molecular beam epitaxy of cubic GaN on Si(001) substrates, which were covered by a 4 nm thick β-SiC layer, is reported. The structural and optical properties of the cubic GaN epilayers were studied by transmission electron microscopy, high-resolution x-ray diffraction, and low-temperature photoluminescence measurements. We find clear evidence for the growth of cubic GaN layers almost free of hexagonal inclusions. The density of extended defects and the near band edge photoluminescence of the cubic GaN layers grown at substrate temperatures of 835 °C is comparable to that of high quality cubic GaN epilayers grown by molecular beam epitaxy on GaAs (001) substrates.

  10. Binding Energy and Dissociation Barrier: Experimental Determination of the Key Parameters of the Potential Energy Curve of Diethyl Ether on Si(001). (United States)

    Reutzel, Marcel; Lipponer, Marcus; Dürr, Michael; Höfer, Ulrich


    The key parameters of the potential energy curve of organic molecules on semiconductor surfaces, binding energy of the intermediate state and dissociation barrier, were experimentally investigated for the model system of diethyl ether (Et2O) on Si(001). Et2O adsorbs via a datively bonded intermediate from which it converts via ether cleavage into a covalently attached final state. This thermally activated conversion into the final state was followed in real-time by means of optical second-harmonic generation (SHG) at different temperatures and the associated energy barrier ϵa = 0.38 ± 0.05 eV and pre-exponential factor νa = 10(4±1) s(-1) were determined. From molecular beam experiments on the initial sticking probability, the difference between the desorption energy ϵd and ϵa was extracted and thus the binding energy of the intermediate state was determined (0.62 ± 0.08 eV). The results are discussed in terms of general chemical trends as well as with respect to a wider applicability on adsorbate reactions on semiconductor surfaces.

  11. Magnetization reversal process in Fe/Si (001) single-crystalline film investigated by planar Hall effect (United States)

    Ye, Jun; He, Wei; Hu, Bo; Tang, Jin; Zhang, Yong-Sheng; Zhang, Xiang-Qun; Chen, Zi-Yu; Cheng, Zhao-Hua


    A planar Hall effect (PHE) is introduced to investigate the magnetization reversal process in single-crystalline iron film grown on a Si (001) substrate. Owing to the domain structure of iron film and the characteristics of PHE, the magnetization switches sharply in an angular range of the external field for two steps of 90° domain wall displacement and one step of 180° domain wall displacement near the easy axis, respectively. However, the magnetization reversal process near the hard axis is completed by only one step of 90° domain wall displacement and then rotates coherently. The magnetization reversal process mechanism near the hard axis seems to be a combination of coherent rotation and domain wall displacement. Furthermore, the domain wall pinning energy and uniaxial magnetic anisotropy energy can also be derived from the PHE measurement. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921801 and 2012CB933102), the National Natural Science Foundation of China (Grant Nos. 11374350, 11034004, 11274361, 11274033, 11474015, and 61227902), and the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20131102130005).

  12. Tunneling magnetoresistance in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Tao, L. L.; Liang, S. H.; Liu, D. P.; Wei, H. X.; Han, X. F., E-mail: [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, Jian [Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong (China)


    We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junction (MTJ). It is found that the spin-polarized conductance and bias-dependent TMR ratios are rather sensitive to the structure of Fe{sub 3}Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized Δ{sub 1} symmetry bands crossing the Fermi level for the cubic Fe{sub 3}Si. In contrast, the tetragonal Fe{sub 3}Si driven by in-plane strain reveals half-metal nature in terms of Δ{sub 1} state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe{sub 3}Si electrodes under zero bias. However, the giant TMR ratio resulting from interface resonant transmission for the former decreases rapidly with the bias. For the latter, the giant TMR ratio can maintain up to larger bias due to coherent transmission through the majority-spin Δ{sub 1} channel.

  13. Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer (United States)

    Li, Qiang; Lai, Billy; Lau, Kei May


    We report epitaxial growth of GaSb nano-ridge structures and planar thin films on V-groove patterned Si (001) substrates by leveraging the aspect ratio trapping technique. GaSb was deposited on {111} Si facets of the V-shaped trenches using metal-organic chemical vapor deposition with a 7 nm GaAs growth initiation layer. Transmission electron microscopy analysis reveals the critical role of the GaAs layer in providing a U-shaped surface for subsequent GaSb epitaxy. A network of misfit dislocations was uncovered at the GaSb/GaAs hetero-interface. We studied the evolution of the lattice relaxation as the growth progresses from closely pitched GaSb ridges to coalesced thin films using x-ray diffraction. The omega rocking curve full-width-at-half-maximum of the resultant GaSb thin film is among the lowest values reported by molecular beam epitaxy, substantiating the effectiveness of the defect necking mechanism. These results thus present promising opportunities for the heterogeneous integration of devices based on 6.1 Å family compound semiconductors.

  14. Vibrational characterization of ethylene adsorption and its thermal evolution on Si(001)-(2 x 1): identification of majority and minority species. (United States)

    Kostov, Krassimir L; Nathaniel, Rachel; Mineva, Tzonka; Widdra, Wolf


    The vibrational and structural properties of a single-domain Si(001)-(2 x 1) surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority species consist of ethylene molecules which are di-sigma bonded to the two Si atoms of a single Si-Si dimer. The local symmetry of this adsorption complex is reduced to C(2) for ethylene saturation coverage as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the C-C bond around the surface normal and the twist of the methylene groups around the C-C axis. Experimentally, 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14% of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules di-sigma bonded to two adjacent Si-Si dimers (in an end-bridge configuration). One part of the minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter, a di-sigma end-bridge like bonding configuration is proposed based on a comparison with vibrational data for adsorbed acetylene on Si(100)-(2 x 1).

  15. Vibrational characterization of ethylene adsorption and its thermal evolution on Si(001)-(2×1): Identification of majority and minority species (United States)

    Kostov, Krassimir L.; Nathaniel, Rachel; Mineva, Tzonka; Widdra, Wolf


    The vibrational and structural properties of a single-domain Si(001)-(2×1) surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority species consist of ethylene molecules which are di-σ bonded to the two Si atoms of a single SiSi dimer. The local symmetry of this adsorption complex is reduced to C2 for ethylene saturation coverage as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the CC bond around the surface normal and the twist of the methylene groups around the CC axis. Experimentally, 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14% of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules di-σ bonded to two adjacent SiSi dimers (in an end-bridge configuration). One part of the minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter, a di-σ end-bridge like bonding configuration is proposed based on a comparison with vibrational data for adsorbed acetylene on Si(100)-(2×1).

  16. In situ RHEED analysis of epitaxial Gd{sub 2}O{sub 3} thin films grown on Si (001)

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, W.F. [China University of Petroleum, State Key Laboratory of Heavy Oil Processing, Beijing (China); China University of Petroleum, Laboratory of Optic Sensing and Detecting Technology, Beijing (China); Chinese Academy of Sciences, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Beijing (China); Ni, H. [China University of Petroleum, Laboratory of Optic Sensing and Detecting Technology, Beijing (China); Lu, H.B. [Chinese Academy of Sciences, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Beijing (China)


    Epitaxial Gd{sub 2}O{sub 3} thin films were successfully grown on Si (001) substrates using a two-step approach by laser molecular-beam epitaxy. At the first step, a {proportional_to}0.8 nm thin layer was deposited at the temperature of 200 {sup circle} C as the buffer layer. Then the substrate temperature was increased to 650 {sup circle} C and in situ annealing for 5 min, and a second Gd{sub 2}O{sub 3} layer with a desired thickness was deposited. The whole growth process is monitored by in situ reflection high-energy electron diffraction (RHEED). In situ RHEED analysis of the growing film has revealed that the first Gd{sub 2}O{sub 3} layer deposition and in situ annealing are the critical processes for the epitaxial growth of Gd{sub 2}O{sub 3} film. The Gd{sub 2}O{sub 3} film has a monoclinic phase characterized by X-ray diffraction. The high-resolution transmission electron microscopy image showed all the Gd{sub 2}O{sub 3} layers have a little bending because of the stress. In addition, a 5-6 nm amorphous interfacial layer between the Gd{sub 2}O{sub 3} film and Si substrate is due to the in situ high temperature annealing for a long time. The successful Gd{sub 2}O{sub 3}/Si epitaxial growth predicted a possibility to develop the new functional microelectronics devices. (orig.)

  17. Coverage dependent interaction of N2O and O2 with Si(001)2x1 as monitored by the O KLL Auger intensity ratio

    NARCIS (Netherlands)

    Keim, Enrico G.; Wormeester, Herbert


    The adsorption behavior of O2 on Si(001)2×1 at 100 K sample temperature has been studied by measuring the intensity ratio of the KL 1 L 1 and KL 2,3 L 2,3 O Auger transitions α as a function of the fractional oxygen coverage in an attempt to solve a longstanding discussion whether this reaction also

  18. Superconducting epitaxial YBa2Cu3O7−δ on SrTiO3-buffered Si(001)

    Indian Academy of Sciences (India)


    Feb 5, 2018 ... cells (Veeco, SVT Associates), and fluxes are measured using a quartz crystal microbalance (Inficon). The silicon wafer is continuously rotated to maintain uniform deposition. The substrate is then heated to 860. ◦. C at which the Sr reacts to form SrO, which readily desorbs from the clean Si surface.

  19. Radio-frequency MBE growth of cubic GaN on BP(001)/Si(001) hetero-structure (United States)

    Kikuchi, T.; Somintac, A. S.; Odawara, M.; Udagawa, T.; Ohachi, T.


    Zincblende gallium nitride (c-GaN) was grown on zincblende boron monophosphide (BP)/silicon (001) using radio-frequency plasma-assisted molecular-beam epitaxy (RF-MBE). In spite of near perfect lattice-match coordination between c-GaN and BP, the initial nucleation of c-GaN was 3D island formation due to imperfect wetting. Using cross-sectional electron backscatter diffraction pattern (x-EBSD), it was found that dislocations were eliminated with an increase of epilayer thickness of c-GaN, and finally 99.4% c-GaN (001) was achieved. The (2x2) and (4x1) reconstructions of the surface of almost pure c-GaN (001) were confirmed by reflection high-energy electron diffraction (RHEED) under arsenic-contamination-free conditions.

  20. Control of tensile strain and interdiffusion in Ge/Si(001) epilayers grown by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Luong, T. K. P.; Dau, M. T.; Zrir, M. A.; Le Thanh, V.; Petit, M. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Stoffel, M.; Rinnert, H. [Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Ghrib, A.; El Kurdi, M.; Boucaud, P. [Institut d' Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Ba-carett. 220, 91405 Orsay (France); Murota, J. [Research Institute of Electrical Communications, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)


    Tensile-strained and n-doped Ge has emerged as a potential candidate for the realization of optoelectronic devices that are compatible with the mainstream silicon technology. Tensile-strained Ge/Si epilayers can be obtained by using the difference of thermal expansion coefficients between Ge and Si. We have combined various surface, structural, and compositional characterizations to investigate the growth mode and the strain state in Ge/Si epilayers grown by molecular-beam epitaxy. The Ge growth was carried out using a two-step approach: a low-temperature growth to produce relaxed and smooth buffer layers, which is followed by a high-temperature growth to get high quality Ge layers. The existence of a substrate temperature window from 260 to 300 °C is evidenced, which allows to completely suppress the Ge/Si Stranski-Krastanov growth. As a consequence of the high temperature growth, a tensile strain lying in the range of 0.22%–0.24% is obtained. Concerning the effect of thermal annealing, it is shown that cyclic annealing may allow increasing the tensile strain up to 0.30%. Finally, we propose an approach to use carbon adsorption to suppress Si/Ge interdiffusion, which represents one of the main obstacles to overcome in order to realize pure Ge-based optoelectronic devices.

  1. Integration of GaN Crystals on Micropatterned Si(001) Substrates by Plasma-Assisted Molecular Beam Epitaxy (United States)

    Isa, Fabio; Cheze, Caroline; Siekacz, Marcin; Hauswald, Christian; Lähnemann, Jonas; Fernandez-Garrido, Sergio; Kreiliger, Thomas; Ramsteiner, Manfred; Dasilva, Yadira Arroyo Rojas; Brandt, Oliver; Isella, Giovanni; Erni, Rolf; Calarco, Raffaella; Riechert, Henning; Miglio, Leo


    We present an innovative approach to integrate arrays of isolated, strain-free GaN crystals on patterned Si substrates. First, micrometer-sized pillars are patterned onto Si(0 0 1) substrates. Subsequently, 2.5 mu m Si substrates are deposited by low-energy plasma-enhanced chemical vapor deposition, forming crystals mostly bounded by {1 1 1}, {1 1 3}, and {15 3 23} facets. Plasma-assisted molecular beam epitaxy is then used for GaN deposition. GaN crystals with slanted {0 0 0 1} facets having a root-mean-square surface roughness of 0.7 nm are obtained for a deposited material thickness of >3 mu m. Microphotoluminescence measurements performed at room and cryogenic temperature show no yellow luminescence and a neutral donor-bound A exciton transition at 3.471 eV (10 K) with a full width at half-maximum of 10 meV. Microphotoluminescence and micro-Raman spectra reveal that GaN grown on Si pillars is strain-free. Our results indicate that the shape of GaN crystals can be tuned by the pattern periodicity and that a reduction of threading dislocations is achieved in their top part.

  2. Direct epitaxial growth of SrTiO{sub 3} on Si (001): Interface, crystallization and IR evidence of phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Niu, G. [Institut des Nanotechnologies de Lyon (INL), Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Peng, W.W. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette (France); Saint-Girons, G.; Penuelas, J. [Institut des Nanotechnologies de Lyon (INL), Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Roy, P.; Brubach, J.B. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette (France); Maurice, J-L. [Unite Mixte de Physique CNRS/Thales Associee a l' Universite Paris Sud, Campus de Polytechnique, 1 Avenue A. Fresnel, 91767 Palaiseau (France); Hollinger, G. [Institut des Nanotechnologies de Lyon (INL), Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Vilquin, B., E-mail: [Institut des Nanotechnologies de Lyon (INL), Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France)


    The work reports the direct epitaxial growth of SrTiO{sub 3} on Si (001) substrate by molecular beam epitaxy. The impact of the growth temperature and the initial oxygen partial pressure on the heteroepitaxy is studied in detail using different in-situ and ex-situ characterization methods. The optimal growth condition has been identified as 360 deg. C with the initial oxygen partial pressure of 5 x 10{sup -8} Torr to achieve a high-quality single crystalline SrTiO{sub 3} film and a coherent interface between SrTiO{sub 3} and Si. The THz Infrared (IR) measurements show that the biaxial strained SrTiO{sub 3} commensurately grown on silicon undergoes a cubic-tetragonal phase transition.

  3. Oxidation process dependence of strain field under the SiO{sub 2}/Si(001) interface revealed by X-ray multiple-wave diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yashiro, W [Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Yoda, Y [Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Kouto, Sayo-gun, Sayo-cho, Hyogo 679-5198 (Japan); Takahashi, K [Department of Electrical and Electronic Engineering, Musashi Institute of Technology, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan); Yamamoto, M [New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Hattori, T [New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Miki, K [National Research Institute of Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)


    A multiple-wave X-ray diffraction phenomenon, i.e., interaction between Bragg reflection and crystal-truncation-rod (CTR) scattering, is applied to characterize strain field under SiO{sub 2}/Si(001) interface. Application of this phenomenon to strain characterization allows us to reveal that there is very small strain field extending over a mesoscopic-scale depth under the SiO{sub 2}/Si interface and having a static fluctuation in the lateral direction. It also allows us to obtain information on distribution of strain field. In this paper oxidation-process dependence of strain distribution is discussed: some recently obtained results of wet oxidations at 900 deg. C and 1100 deg. C are compared with those of dry oxidation and Kr/O{sub 2} plasma oxidation.

  4. Stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells, grown on GaAs and Ge/Si(001) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yablonsky, A. N., E-mail:; Morozov, S. V.; Gaponova, D. M.; Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Shengurov, V. G.; Zvonkov, B. N.; Vikhrova, O. V.; Baidus’, N. V. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Krasil’nik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)


    We report the observation of stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells, grown on Si(001) substrates with the application of a relaxed Ge buffer layer. Stimulated emission is observed at 77 K under pulsed optical pumping at a wavelength of 1.11 μm, i.e., in the transparency range of bulk silicon. In similar InGaAs/GaAsSb/GaAs structures grown on GaAs substrates, room-temperature stimulated emission is observed at 1.17 μm. The results obtained are promising for integration of the structures into silicon-based optoelectronics.

  5. Influence of the wetting-layer growth kinetics on the size and shape of Ge self-assembled quantum dots on Si(001) (United States)

    Kim, H. J.; Xie, Y. H.


    The growth temperature of the wetting layer is used as the key variable in the study of a series of Ge self-assembled quantum dots on Si(001) substrates. A relaxed SiGe buffer layer is used for most of the samples as a means of maintaining the density of Ge dots. Ge dots are in the shapes of pyramids, domes, and superdomes, similar to those reported in the literature. A significant difference in the fraction of pyramids is observed between samples with wetting layers grown at low (280 °C) and high (650 °C) temperatures. This difference is in turn dependent on the total amount of Ge deposited or equivalently, the average size of dots. These observations point to the presence of Si during the initial stage of Ge dot formation and that the fraction of pyramids as well as the critical size for the transition from pyramids to domes are influenced by the presence of Si.

  6. Epitaxial grown InP quantum dots on a GaAs buffer realized on GaP/Si(001) templates

    Energy Technology Data Exchange (ETDEWEB)

    Hartwig, Walter; Wiesner, Michael; Koroknay, Elisabeth; Paul, Matthias; Jetter, Michael; Michler, Peter [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen und Research Center SCoPE, Universitaet Stuttgart, Allmandring 3, 70569 Stuttgart (Germany)


    The increasing necessity of higher computational capacity and security in the information technology requires originally technical solutions, which today's standard microelectronics, as their technical limits are close, can't provide anymore. One way out offers the integration of III-V semiconductor photonics with low-dimensional structures in current CMOS technology, enabling on-chip quantum optical applications, like quantum cryptography or quantum computing. Challenges in the heteroepitaxy of III-V semiconductors and silicon are the mismatches in material properties of the both systems. Defects, like dislocations and anti-phase domains (APDs), inhibit the monolithic integration of III-V semiconductor on Si. We present the growth of a thin GaAs buffer on CMOS-compatible oriented Si(001) by metal-organic vapor-phase epitaxy. To circumvent the forming APDs in the GaAs buffer a GaP on Si template (provided by NAsP{sub III/V} GmbH) was used. The dislocation density was then reduced by integrating several layers of InAs quantum dots in the GaAs buffer to bend the threading misfit dislocations. On top of this structure we grew InP quantum dots embedded in a Al{sub x}Ga{sub 1-x}InP composition and investigated the photoluminescence properties.

  7. Influence of composition and substrate miscut on the evolution of {105}-terminated in-plane Si1−xGex quantum wires on Si(001

    Directory of Open Access Journals (Sweden)

    H. Watzinger


    Full Text Available Isolated in-plane wires on Si(001 are promising nanostructures for quantum transport applications. They can be fabricated in a catalyst-free process by thermal annealing of self-organized Si1−xGex hut clusters. Here, we report on the influence of composition and small substrate miscuts on the unilateral wire growth during annealing at 570 °C. The addition of up to 20% of Si mainly affects the growth kinetics in the presence of energetically favorable sinks for diffusing Ge atoms, but does not significantly change the wire base width. For the investigated substrate miscuts of <0.12°, we find geometry-induced wire tapering, but no strong influence on the wire lengths. Miscuts <0.02° lead to almost perfect quantum wires terminated by virtually step-free {105} and {001} facets over lengths of several 100 nm. Generally, the investigated Si1−xGex wires are metastable: Annealing at ≥600 °C under otherwise identical conditions leads to the well-known coexistence of Si1−xGex pyramids and domes.

  8. Molecular-beam epitaxial growth of tensile-strained and n-doped Ge/Si(001) films using a GaP decomposition source

    Energy Technology Data Exchange (ETDEWEB)

    Luong, T.K.P. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Ghrib, A. [Institut d' Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Bât. 220, F-91405 Orsay (France); Dau, M.T.; Zrir, M.A. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Stoffel, M. [Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 70239, F-54506 Vandoeuvre-lès-Nancy Cedex (France); Le Thanh, V., E-mail: [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Daineche, R. [Aix-Marseille Université, CNRS IM2NP-UMR 6242, F-13397 Marseille Cedex 20 (France); Le, T.G.; Heresanu, V.; Abbes, O.; Petit, M. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); El Kurdi, M.; Boucaud, P. [Institut d' Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Bât. 220, F-91405 Orsay (France); Rinnert, H. [Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 70239, F-54506 Vandoeuvre-lès-Nancy Cedex (France); Murota, J. [Res. Inst. Elec. Comm., Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)


    We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski–Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260 °C and 300 °C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700–770 °C are tensile-strained with typical values lying in the range of 0.22–0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210–250 °C). For a GaP source temperature of 725 °C and a substrate temperature of 210 °C, a phosphorus concentration of about 10{sup 19} cm{sup −3} can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25 meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications. - Highlights: • We investigate the effect of tensile strain and n-doping on Ge optical properties. • We show that cyclic annealing allows getting a tensile strain up to 0.30% in Ge. • n-Doping of Ge/Si films is performed using a GaP decomposition source. • We show that n-doping is more important to enhance the photoluminescence intensity. • We present new growth strategies to develop Ge

  9. Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 °C

    National Research Council Canada - National Science Library

    Storozhevykh, Mikhail S; Arapkina, Larisa V; Yuryev, Vladimir A


    .... The experiment has demonstrated that the Ge/Si(001) film formed in the conditions of an isolated system consists of the standard patched wetting layer and large droplike clusters of Ge rather than of huts or domes which appear when a film is grown...

  10. Orientation of FePt nanoparticles on top of a-SiO2/Si(001, MgO(001 and sapphire(0001: effect of thermal treatments and influence of substrate and particle size

    Directory of Open Access Journals (Sweden)

    Martin Schilling


    Full Text Available Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001, i.e., Si(001 with an amorphous (a- native oxide layer on top, on MgO(001, and on sapphire(0001 substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: “small” NPs with diameters in the range of 2–3 nm and “large” ones in the range of 5–8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD, served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001 supports, however, FePt nanoparticles exhibit a clearly preferred (111 orientation even in the as-prepared state, which can be slightly improved by annealing at 600–650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111 orientation. On top of MgO(001 the

  11. Structural properties of the formation of zinc-containing nanoparticles obtained by ion implantation in Si (001 and subsequent thermal annealing

    Directory of Open Access Journals (Sweden)

    Ksenia B. Eidelman


    We show that a damaged layer with a large concentration of radiation induced defects forms near the surface as a result of the implantation of Zn+ ions with an energy of 50 keV. In the as-implanted state, nanoparticles of metallic Zn with a size of about 25 nm form at a depth of 40 nm inside the damaged silicon layer. Subsequent annealing at 800 °C in a dry oxygen atmosphere leads to structural changes in the defect layer and the formation of Zn2SiO4 nanoparticles at a depth of 25 nm with an average size of 3 nm, as well as oxidation of the existing Zn particles to the Zn2SiO4 phase. The oxidation of the metallic Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core-shell” structure. Analysis of the phase composition of the silicon layer after two-stage implantation with O+ and Zn+ ions showed that Zn and Zn2SiO4 particles form in the as-implanted state. Subsequent annealing at 800 °C in a dry oxygen atmosphere leads to an increase in the particle size but does not change the phase composition of the near-surface layer. ZnO nanoparticles were not observed under these experimental conditions of ion beam synthesis.

  12. Soft x-ray photoemission study of the thermal stability of the Al2O3/Ge (100) interface as a function of surface preparation (United States)

    Chellappan, Rajesh Kumar; Rao Gajula, Durga; McNeill, David; Hughes, Greg


    The high temperature thermal stability of ultra-thin atomic layer deposited Al2O3 on sulphur passivated and hydrofluoric acid (HF) treated germanium surfaces was studied using soft x-ray photoemission spectroscopy. The interface sulphur component was stable up to 500 °C vacuum annealing. The interfacial oxides were completely removed at 600 °C for the sulphur passivated sample, whereas HF treated sample showed traces of residual oxides at the interface. However, this annealing treatment does not show any significant change in Al2O3 stoichiometry. The dielectric-semiconductor band offsets were estimated using photoemission spectroscopy measurements.

  13. Search for a metallic dangling-bond wire on n-doped H-passivated semiconductor surfaces

    DEFF Research Database (Denmark)

    Engelund, Mads; Papior, Nick Rübner; Brandimarte, Pedro


    We have theoretically investigated the electronic properties of neutral and n-doped dangling bond (DB) quasi-one-dimensional structures (lines) in the Si(001):H and Ge(001):H substrates with the aim of identifying atomic-scale interconnects exhibiting metallic conduction for use in on-surface cir...

  14. Half-metallicity and magnetism at Heusler alloy surfaces: Co{sub 2}MSi(001)(M=Ti,Cr)

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Ying Jiu [Department of Physics, Inha University, Incheon (Korea); Department of Physics, College of Science, Yanbian University, Yanji, Jilin (China); Lee, Jae Il [Department of Physics, Inha University, Incheon (Korea)


    We investigated the electronic structures, magnetism, and half-metallicity at the (001) surfaces of full-Heusler alloys, Co{sub 2}MSi (M=Ti,Cr), by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. Both the Co-terminated (Co-term) and the MSi-terminated (MSi-term) surfaces were considered. From the calculated atom-resolved density of states, we found that the half-metallicity was destroyed at the Co-term surfaces for both alloys. The electronic structures at the MSi-term surfaces of the two alloys showed much different behavior. The half-metallicity was retained at the TiSi-term for Co{sub 2}TiSi(001) but the minority spin gap was much reduced due to surface states located just below the Fermi level. On the other hand the half-metallicity was destroyed at the CrSi-term of Co{sub 2}CrSi(001) due to the surface states located at the Fermi level. The calculated magnetic moment of the surface Co atom of the Co-term for Co{sub 2}CrSi(001) was increased slightly to 1.05 {mu}{sub B} with respect to that of the deep inner layers ({proportional_to}1.00{mu}{sub B}), while that for Co{sub 2}TiSi(001) was decreased to 0.88 {mu}{sub B}. Large enhancement of the magnetic moment was found for the surface Ti atoms at TiSi-term of Co{sub 2}TiSi(001) and Cr atoms at CrSi-term of Co{sub 2}CrSi(001) with values of 0.07 {mu}{sub B} and 2.91({mu}{sub B}), respectively. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Boron diffusion in Ge{sup +} premorphized and BF{sub 2} implanted Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Zou, L.F.; Acosta-Ortiz, S.E. [Centro de Investigaciones en Optica, A.C. Unidad Aguascalientes, Juan de Montoro No. 207, Zona Centro, 20000 Aguascalientes (Mexico); Zou, L.X. [Computer Science Department, Zhongnan University for Nationalities Wuhan, Hubei 430074 (China); Regalado, L.E. [Centro de Investigaciones en Optica, Loma del Bosque No. 115, Loma del Campestre, 37000 Leon, Gunajuato (Mexico); Sun, D.Z.; Wang, Z.G. [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, (China)


    The annealing behavior of Si implanted with Ge and then BF{sub 2} has been characterized by double crystal X-ray diffraction (DCXRD) and secondary ion mass spectroscopy (SIMS). The results show that annealing at 600 Centigrade for 60 minutes can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. The initial crystallinity of Si is fully recovered after annealing at 950 Centigrade for 60 minutes and accompanied by Ge diffusion. Very shallow boron junction depth has been formed. When annealing temperature rises to 1050 Centigrade, B diffusion enhances, which leads to a deep diffusion and good distribution of B atoms into the Si substrate. The X-ray diffraction (004) rocking curves from the samples annealed at 1050 Centigrade for 60 minutes display two Si Ge peaks, which may be related to the B concentration profiles. (Author)

  16. Electromagnetic excitation of phonons at C(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Sanchez, F L [Escuela de Ciencias, Universidad Autonoma ' Benito Juarez' de Oaxaca, Avenida Universidad S/N, Ex-Hacienda de Cinco Senores, Ciudad Universitaria, Oaxaca de Juarez, Oaxaca, 68120 (Mexico); Perez-Rodriguez, F, E-mail: fperez@sirio.ifuap.buap.m [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apartado Post. J-48, Puebla 72570 (Mexico)


    The photon-phonon coupling at C(001)-(2 x 1) surfaces and its manifestation in far-infrared reflectance anisotropy spectra (FIR-RAS) are theoretically investigated. We solve the coupled system of equations for the electromagnetic field and lattice vibrations, described within the adiabatic bond charge model (ABCM), with the method of expansion into bulk phonon and photon modes. The calculated FIR-RAS exhibit resonances associated with zone-center surface phonons in good agreement with available HREELS experiments and predictions of vibrational modes for diamond (001)-(2 x 1) surfaces from ABCM and ab initio calculations. Interestingly, the reflectance anisotropy spectra for a C(001)-(2 x 1) surface turn out to be qualitatively different from the spectra for a Si(001)-(2 x 1) surface, reported previously.

  17. A genetic algorithm approach in interface and surface structure optimization

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian [Iowa State Univ., Ames, IA (United States)


    The thesis is divided into two parts. In the first part a global optimization method is developed for the interface and surface structures optimization. Two prototype systems are chosen to be studied. One is Si[001] symmetric tilted grain boundaries and the other is Ag/Au induced Si(111) surface. It is found that Genetic Algorithm is very efficient in finding lowest energy structures in both cases. Not only existing structures in the experiments can be reproduced, but also many new structures can be predicted using Genetic Algorithm. Thus it is shown that Genetic Algorithm is a extremely powerful tool for the material structures predictions. The second part of the thesis is devoted to the explanation of an experimental observation of thermal radiation from three-dimensional tungsten photonic crystal structures. The experimental results seems astounding and confusing, yet the theoretical models in the paper revealed the physics insight behind the phenomena and can well reproduced the experimental results.

  18. Structural, chemical and electronic properties of the Co2MnSi(001)/MgO interface


    Fetzer, Roman; Wüstenberg, Jan-Peter; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Aeschlimann, Martin; Cinchetti, Mirko


    The performance of advanced magnetic tunnel junctions build of ferromagnetic (FM) electrodes and MgO as insulating barrier depends decisively on the properties of the FM/insulator interface. Here, we investigate interface formation between the half-metallic compound Co2MnSi (CMS) and MgO by means of Auger electron spectroscopy, low energy electron diffraction and low energy photoemission. The studies are performed for different annealing temperatures TA and MgO layer coverages (4, 6, 10, 20 a...

  19. Formation and thermoelectric properties of Si/CrSi2/Si(001) heterostructures with stressed chromium disilicide nanocrystallites (United States)

    Goroshko, Dmitry; Chusovitin, Evgeniy; Bezbabniy, Dmitry; Dózsa, Laszlo; Pécz, Bela; Galkin, Nikolay


    Three-layer heterostructures with embedded CrSi2 nanocrystallites were grown using molecular-beam epitaxy. The nanocrystallites have epitaxial orientation to the silicon lattice and are subjected to anisotropic compressive stress in the CrSi2 [001] direction. The thermoelectric power factor of the heterostructure is about 5 times higher than that in the substrate at 300-480 K. Taking into consideration the ratio of nanocomposite and substrate thickness, the real power factor is expected to be 2-3 orders higher than the measured one and it reaches 3200 μW K-2 m-1 at 470 K.[Figure not available: see fulltext.

  20. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.


    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  1. My Research History on the Chemical Standpoint-From Molecular Structure to Surface Science. (United States)

    Murata, Yoshitada


    The structure of molecules using gas electron diffraction (GED) was my graduate study. However, I was making a new apparatus for precise measurements by GED and formulated a scheme for the least-squares analysis for a smooth continuous curve of scattering intensity. My research was completely shifted to the solid surface after moving to Gakushuin University, where I briefly studied the liquid structure of CCl4 molecules, and I then moved to the Institute for Solid State Physics, the University of Tokyo. My studies of surface science were focused on the electronic properties and related phenomena, and various experimental methods were developed. The plasmon dispersions elucidated the initial oxidation of aluminum and one-dimensional metal on Si(001)2 × 1-K. Irreversible phase transition was discovered on MgO(001) using the LEED Kikuchi pattern. The electronic structure of the dislocation was observed on MgO(001) by the electron time-of-flight method. The phase transition on Si(001) and the rotational epitaxy in a K monoatomic layer on Cu(001) were found. Next, I changed to studies of the dynamical phenomena on the surface, where very low energy reactive ion scattering on metal surfaces and laser-induced desorption caused by electronic transition of NO and CO molecules from metal surfaces were observed, and the hydrogen atom location at the surface and interface was measured with a high depth resolution using a resonance nuclear reaction of (1) H + (15) N(2+) at 6.385 MeV. Finally, I moved to the University of Electro-Communications and studied thin single-crystal oxide layers on transition metals, in which the band-gap narrowing was found, and then a Pt monoatomic layer was prepared on the α-Al(2)O(3) film. Copyright © 2015 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Search for a metallic dangling-bond wire on n-doped H-passivated semiconductor surfaces

    DEFF Research Database (Denmark)

    Engelund, Mads; Papior, Nick Rübner; Brandimarte, Pedro


    We have theoretically investigated the electronic properties of neutral and n-doped dangling bond (DB) quasi-one-dimensional structures (lines) in the Si(001):H and Ge(001):H substrates with the aim of identifying atomic-scale interconnects exhibiting metallic conduction for use in on-surface cir......We have theoretically investigated the electronic properties of neutral and n-doped dangling bond (DB) quasi-one-dimensional structures (lines) in the Si(001):H and Ge(001):H substrates with the aim of identifying atomic-scale interconnects exhibiting metallic conduction for use in on......-surface circuitry. Whether neutral or doped, DB lines are prone to suffer geometrical distortions or have magnetic ground states that render them semiconducting. However, from our study we have identified one exception - a dimer row fully stripped of hydrogen passivation. Such a DB-dimer line shows an electronic...... band structure which is remarkably insensitive to the doping level, and thus, it is possible to manipulate the position of the Fermi level, moving it away from the gap. Transport calculations demonstrate that the metallic conduction in the DB-dimer line can survive thermally induced disorder...

  3. Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment. (United States)

    Liu, Neng; Moumanis, Khalid; Dubowski, Jan J


    The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75°. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm(2), respectively, has decreased the CA to near 15°, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer's surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm(2) and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103°. The XPS results indicate ArF laser induced formation of Si-(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

  4. Scanning electron microscope comparative surface evaluation of glazed-lithium disilicate ceramics under different irradiation settings of Nd:YAG and Er:YAG lasers. (United States)

    Viskic, Josko; Jokic, Drazen; Jakovljevic, Suzana; Bergman, Lana; Ortolan, Sladana Milardovic; Mestrovic, Senka; Mehulic, Ketij


    To evaluate the surface of glazed lithium disilicate dental ceramics after irradiation under different irradiation settings of Nd:YAG and Er:YAG lasers using a scanning electron microscope (SEM). Three glazed-press lithium disilicate ceramic discs were treated with HF, Er:YAG, and Nd:YAG, respectively. The laser-setting variables tested were laser mode, repetition rate (Hz), power (W), time of exposure (seconds), and laser energy (mJ). Sixteen different variable settings were tested for each laser type, and all the samples were analyzed by SEM at 500× and 1000× magnification. Surface analysis of the HF-treated sample showed a typical surface texture with a homogenously rough pattern and exposed ceramic crystals. Er:YAG showed no effect on the surface under any irradiation setting. The surface of Nd:YAG-irradiated samples showed cracking, melting, and resolidifying of the ceramic glaze. These changes became more pronounced as the power increased. At the highest power setting (2.25 W), craters on the surface with large areas of melted or resolidified glaze surrounded by globules were visible. However, there was little to no exposure of ceramic crystals or visible regular surface roughening. Neither Er:YAG nor Nd:YAG dental lasers exhibited adequate surface modification for bonding of orthodontic brackets on glazed lithium disilicate ceramics compared with the control treated with 9.5% HF.

  5. Metal positioning on silicon surfaces using the etching of buried dislocation arrays. (United States)

    Bavard, A; Fournel, F; Eymery, J


    Large-area Si(001) nanopatterned surfaces obtained by etching dislocation line arrays have been used to drive the positioning of metallic islands. A method combining wafer bonding of (001) silicon on insulator layers and preferential chemical etching allows controlling the periodicity of square trench arrays in the 20-50 nm lateral periodicity range with an accuracy of less than 1 nm and a depth of about 4-5 nm. The interfacial area containing the dislocation line plane can be removed and a single crystal maintaining the morphological patterning can be obtained. It is shown that oxidized or deoxidized silicon nanopatterned surfaces can drive the positioning of Ni, Au and Ag islands for a 20 nm lateral periodicity and that a lateral long range order, directly transferred from the dislocation network, can be obtained in the Ni and Au cases.

  6. Rare earth silicide nanowires on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wanke, Martina


    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti {gamma} point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi{sub 2}-monolayer and the Dy{sub 3}Si{sub 5}-multilayer on the Si(111) surface are investigated in comparison to the known ErSi{sub 2}/Si(111) and Er{sub 3}Si{sub 5}/Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the (vector)k {sub parallel} space is elliptical at the anti M points, while the hole pocket at the anti {gamma} point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas

  7. Surface Water & Surface Drainage (United States)

    Earth Data Analysis Center, University of New Mexico — This data set contains boundaries for all surface water and surface drainage for the state of New Mexico. It is in a vector digital data structure digitized from a...

  8. Toward Accurate Reaction Energetics for Molecular Line Growth at Surface: Quantum Monte Carlo and Density Functional Theory Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Kanai, Y; Takeuchi, N


    We revisit the molecular line growth mechanism of styrene on the hydrogenated Si(001) 2x1 surface. In particular, we investigate the energetics of the radical chain reaction mechanism by means of diffusion quantum Monte Carlo (QMC) and density functional theory (DFT) calculations. For the exchange correlation (XC) functional we use the non-empirical generalized-gradient approximation (GGA) and meta-GGA. We find that the QMC result also predicts the intra dimer-row growth of the molecular line over the inter dimer-row growth, supporting the conclusion based on DFT results. However, the absolute magnitudes of the adsorption and reaction energies, and the heights of the energy barriers differ considerably between the QMC and DFT with the GGA/meta-GGA XC functionals.

  9. Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates (United States)

    Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.


    Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

  10. Atomic structure of the indium-induced Ge(001)(¤n¤x4) surface reconstruction determined by scanning tunneling microscopy and ¤ab initio¤ calculations

    DEFF Research Database (Denmark)

    Falkenberg, G.; Bunk, O.; Johnson, R.L.


    . Sci. 123/124, 104 (1998) for In on Si(001). For the (4x4) subunit, we propose a model that includes the main features of the (3x4) subunit together with additional mixed Ge-In dimers. The atomic positions were optimized using ab initio total-energy calculations. The calculated local densities......Using scanning-tunneling microscopy (STM) and first-principles total-energy calculations, we have determined the atomic geometry of the superstructures formed by the adsorption of up to 0.5 monolayer of indium on Ge(001) and annealing at temperatures above 200 degreesC. A strong interaction between...... indium adatoms and the germanium substrate atoms leads to the formation of two different In-Ge subunits on the Ge(001) surface. In the subsaturation regime separate (nx4) subunits are observed where n can be either 3 or 4 and the STM images resemble those of the Si(001)-(3x4)-In and -Al reconstructions...

  11. Ferromagnetismo robusto em filmes fotoeletrodepositados de CeO2 e CeO2 dopados com Co sobre Si (001) /


    Fernandes, Vilmar


    Orientador: Dante Homero Mosca Dissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçao em Engenharia - PIPE. Defesa: Curitiba, 2007 Inclui bibliografia Área de concentraçao: Engenharia e ciencias de materiais

  12. Comment on "Step dynamics and equilibrium structure of monoatomic steps on Si(001)-2x1" by J.R. Sanchez and C.M. Aldao

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.; Wulfhekel, W.; Wulfhekel, W.C.U.; Hendriksen, B.; Poelsema, Bene


    In contrast to a recent claim by Sánchez and Aldao [Phys. Rev. B 54, R11 058 (1996)] that the relaxation dynamics of attachment processes influences the equilibrium step structure we argue that the step structure in thermodynamic equilibrium is only governed by the configurational free energy

  13. Small-Diameter Silicon Nanowire Surfaces

    National Research Council Canada - National Science Library

    D. D. D. Ma; C. S. Lee; F. C. K. Au; S. Y. Tong; S. T. Lee


    .... Scanning tunneling microscopy (STM) of these SiNWs, performed both in air and in ultrahigh vacuum, revealed atomically resolved images that can be interpreted as hydrogen-terminated Si (111)-(1 x 1) and Si (001)-(1 x 1...

  14. Theoretical study on photon-phonon coupling at (001)-(2 x 1) surfaces of Ge and {alpha}-Sn

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Sanchez, F.L. [Escuela de Ciencias, Universidad Autonoma ' ' Benito Juarez' ' de Oaxaca, Av. Universidad S/N, Ex-Hacienda de Cinco Senores, Ciudad Universitaria, Oaxaca de Juarez, Oax., 68120 (Mexico); Perez-Rodriguez, F. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apdo. Post. J-48, Puebla, Pue. 72570 (Mexico)


    We present a study of the far-infrared reflectance anisotropy spectra for (001) surfaces of Ge and {alpha}-Sn in the (2 x 1) asymmetric dimer geometry, which exhibit a resonance structure associated with the excitation of surface phonon modes. We have employed a theoretical formalism, based on the adiabatic bond-charge model (ABCM), for computing the far-infrared reflectance anisotropy spectra. In comparison with previous theoretical results for silicon and diamond surfaces, the resonance structure in the reflectance anisotropy spectrum for Ge(001)-(2 x 1) turns out to be similar to that observed in the spectrum for the Si(001)-(2 x 1) surface, whereas the spectrum for {alpha}-Sn(001)-(2 x 1) surface is noticeably different from the others. We have established a trend of far-infrared reflectance anisotropy spectra for IV(001) surfaces: the weaker dimer strength, the stronger resonances of low-frequency surface phonons. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Ab initio analysis of a vacancy and a self-interstitial near single crystal silicon surfaces: Implications for intrinsic point defect incorporation during crystal growth from a melt

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, Eiji; Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); Vanhellemont, Jan [Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, Gent 9000 (Belgium)


    The microscopic model of the Si (001) crystal surface was investigated by first principles calculations to clarify the behavior of intrinsic point defects near crystal surfaces. A c(4 x 2) structure model was used to describe the crystal surface in contact with vacuum. The calculations show lower formation energy near the surface and the existence of formation energy differences between the surface and the bulk for both types of intrinsic point defects. The tetrahedral (T)-site and the dumbbell (DB)-site, in which a Si atom is captured from the surface and forms a self-interstitial, are found as stable sites near the third atomic layer. The T-site has a barrier of 0.48 eV, whereas the DB-site has no barrier for the interstitial to penetrate into the crystal from the vacuum. Si atoms in a melt can migrate and reach at the third layer during crystal growth when bulk diffusion coefficient is used. Therefore, the melt/solid interface is always a source of intrinsic point defects. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Surface Tension (United States)

    Theissen, David B.; Man, Kin F.


    The effect of surface tension is observed inmany everyday situations. For example, a slowly leaking faucet drips because the force surface tension allows the water to cling to it until a sufficient mass of water is accumulated to break free.

  17. Superamphiphobic Surfaces

    NARCIS (Netherlands)

    Cavalli, Andrea; Mugele, Friedrich Gunther; Brutin, David


    This chapter discusses recent trends in the development, fabrication, and characterization of superamphiphobic surfaces. An amphiphobic surface repels both polar liquids, such as water, and nonpolar (oily) liquids, and has therefore useful technological application in microfluidics devices,

  18. Rumble surfaces

    CSIR Research Space (South Africa)

    National Institute for Transport and Road


    Full Text Available Rumble surfaces are intermittent short lengths of coarse-textured road surfacings on which vehicle tyres produce a rumbling sound. used in conjunction with appropriate roadsigns and markings, they can reduce accidents on rural roads by alerting...

  19. Spherical Surfaces

    DEFF Research Database (Denmark)

    Brander, David


    We study surfaces of constant positive Gauss curvature in Euclidean 3-space via the harmonicity of the Gauss map. Using the loop group representation, we solve the regular and the singular geometric Cauchy problems for these surfaces, and use these solutions to compute several new examples. We give...

  20. Trapped surfaces

    CERN Document Server

    Senovilla, José M M


    I review the definition and types of (closed) trapped surfaces. Surprising global properties are shown, such as their "clairvoyance" and the possibility that they enter into flat portions of the spacetime. Several results on the interplay of trapped surfaces with vector fields and with spatial hypersurfaces are presented. Applications to the quasi-local definition of Black Holes are discussed, with particular emphasis set onto marginally trapped tubes, trapping horizons and the boundary of the region with closed trapped surfaces. Finally, the core of a trapped region is introduced, and its importance discussed.

  1. Trapped Surfaces (United States)

    Senovilla, José M. M.


    I review the definition and types of (closed) trapped surfaces. Surprising global properties are pointed out, such as their "clairvoyance" and the possibility that they enter into flat portions of the spacetime. Several results on the interplay of trapped surfaces with vector fields and with spatial hypersurfaces are presented. Applications to the quasi-local definition of Black Holes are analyzed, with particular emphasis set onto marginally trapped tubes, trapping horizons and the boundary of the region with closed trapped surfaces. Finally, the core of a trapped region is introduced, and its importance briefly discussed.

  2. Surface optofluidics (United States)

    Vasdekis, A. E.; Cuennet, J. G.; Song, W. Z.; Choi, J.-W.; De Sio, L.; O'Neil, C. P.; Hubbell, J. A.; Psaltis, D.


    Surfaces -defined as the interfaces between solids and liquids- have attracted much attention in optics and biology, such as total internal reflection imaging (TIRF) and DNA microarrays. Within the context of optofluidics however, surfaces have received little attention. In this paper, we describe how surfaces can define or enhance optofluidic function. More specifically we discuss chemical interfaces that control the orientation of liquid crystals and the stretching of individual nucleic acids, diffractive and plasmonic nanostructures for lasing and opto-thermal control, as well as microstructures that read pressure and form chemical patterns.

  3. Surface boxplots

    KAUST Repository

    Genton, Marc G.


    In this paper, we introduce a surface boxplot as a tool for visualization and exploratory analysis of samples of images. First, we use the notion of volume depth to order the images viewed as surfaces. In particular, we define the median image. We use an exact and fast algorithm for the ranking of the images. This allows us to detect potential outlying images that often contain interesting features not present in most of the images. Second, we build a graphical tool to visualize the surface boxplot and its various characteristics. A graph and histogram of the volume depth values allow us to identify images of interest. The code is available in the supporting information of this paper. We apply our surface boxplot to a sample of brain images and to a sample of climate model outputs.

  4. Convex surfaces

    CERN Document Server

    Busemann, Herbert


    This exploration of convex surfaces focuses on extrinsic geometry and applications of the Brunn-Minkowski theory. It also examines intrinsic geometry and the realization of intrinsic metrics. 1958 edition.

  5. Surface phonons

    CERN Document Server

    Wette, Frederik


    In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech­ niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen­ tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, co...

  6. EDITORIAL: Focus on Advances in Surface and Interface Science 2008 FOCUS ON ADVANCES IN SURFACE AND INTERFACE SCIENCE 2008 (United States)

    Scheffler, Matthias; Schneider, Wolf-Dieter


    Iori, K Sakamoto, H Narita, A Kimura, M Taniguchi, S Qiao, K Hasegawa, K Shimada, H Namatame and S Blügel Activated associative desorption of C + O → CO from Ru(001) induced by femtosecond laser pulses S Wagner, H Öström, A Kaebe, M Krenz, M Wolf, A C Luntz and C Frischkorn Surface structure of Sn-doped In2O3 (111) thin films by STM Erie H Morales, Yunbin He, Mykola Vinnichenko, Bernard Delley and Ulrike Diebold Coulomb oscillations in three-layer graphene nanostructures J Güttinger, C Stampfer, F Molitor, D Graf, T Ihn and K Ensslin Adsorption processes of hydrogen molecules on SiC(001), Si(001) and C(001) surfaces Xiangyang Peng, Peter Krüger and Johannes Pollmann Fermi surface nesting in several transition metal dichalcogenides D S Inosov, V B Zabolotnyy, D V Evtushinsky, A A Kordyuk, B Büchner, R Follath, H Berger and S V Borisenko Probing molecule-surface interactions through ultra-fast adsorbate dynamics: propane/Pt(111) A P Jardine, H Hedgeland, D Ward, Y Xiaoqing, W Allison, J Ellis and G Alexandrowicz A novel method achieving ultra-high geometrical resolution in scanning tunnelling microscopy R Temirov, S Soubatch, O Neucheva, A C Lassise and F S Tautz

  7. Ice Surfaces (United States)

    Shultz, Mary Jane


    Ice is a fundamental solid with important environmental, biological, geological, and extraterrestrial impact. The stable form of ice at atmospheric pressure is hexagonal ice, Ih. Despite its prevalence, Ih remains an enigmatic solid, in part due to challenges in preparing samples for fundamental studies. Surfaces of ice present even greater challenges. Recently developed methods for preparation of large single-crystal samples make it possible to reproducibly prepare any chosen face to address numerous fundamental questions. This review describes preparation methods along with results that firmly establish the connection between the macroscopic structure (observed in snowflakes, microcrystallites, or etch pits) and the molecular-level configuration (detected with X-ray or electron scattering techniques). Selected results of probing interactions at the ice surface, including growth from the melt, surface vibrations, and characterization of the quasi-liquid layer, are discussed.

  8. Surfacing Moves

    DEFF Research Database (Denmark)

    Lutz, Peter


    -management policies that pressure such care in practice. Some scholars analyze this situation as opposition between ‘objective’ and ‘subjective’ time. This article takes a different route. It explores how time surfaces in Swedish senior home care through relational movements of care. These enlist things...... such as schedules, machines, and aging bodies. To this end, the article also experiments with ‘surfacing’ as an ethnographic heuristic for figuring these different ‘spatial-timings’. The article concludes that surfacing matters not only in senior home care but also in the field-desks of ethnographic analysis....

  9. Attack surfaces

    DEFF Research Database (Denmark)

    Gruschka, Nils; Jensen, Meiko


    The new paradigm of cloud computing poses severe security risks to its adopters. In order to cope with these risks, appropriate taxonomies and classification criteria for attacks on cloud computing are required. In this work-in-progress paper we present one such taxonomy based on the notion...... of attack surfaces of the cloud computing scenario participants....

  10. Describing Surfaces. (United States)


    lightbulb. It is well-known (for exam~ple, do Carmo "" "..-’,.’.V .. .V...i ra I s ; ul ing-.. "’. Figure 11. The helicoid of a single blade. (Reproduced from [do Carmo 1976, Figure 2-27 Page 94]) where m and 1 are assumed...York. Do Carmo , Manfredo P, [1976], Differential Geometry of Curves and Surfaces, Prent- ice-Hall, Englewood Cliffs, NJ. Faugeras, 0. D., et. al, [1982

  11. Non-adiabatic processes in the charge transfer reaction of O{sub 2} molecules with potassium surfaces without dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Krix, David; Nienhaus, Hermann, E-mail: [Faculty of Physics, University of Duisburg-Essen and Center of Nanointegration Duisburg-Essen (CENIDE), Lotharstr. 1, D-47048 Duisburg (Germany)


    Thin potassium films grown on Si(001) substrates are used to measure internal chemicurrents and the external emission of exoelectrons simultaneously during adsorption of molecular oxygen on K surfaces at 120 K. The experiments clarify the dynamics of electronic excitations at a simple metal with a narrow valence band. X-ray photoemission reveals that for exposures below 5 L almost exclusively peroxide K{sub 2}O{sub 2} is formed, i.e., no dissociation of the molecule occurs during interaction. Still a significant chemicurrent and a delayed exoelectron emission are detected due to a rapid injection of unoccupied molecular levels below the Fermi level. Since the valence band width of potassium is approximately equal to the potassium work function (2.4 eV) the underlying mechanism of exoemission is an Auger relaxation whereas chemicurrents are detected after resonant charge transfer from the metal valence band into the injected level. The change of the chemicurrent and exoemission efficiencies with oxygen coverage can be deduced from the kinetics of the reaction and the recorded internal and external emission currents traces. It is shown that the non-adiabaticity of the reaction increases with coverage due to a reduction of the electronic density of states at the surface while the work function does not vary significantly. Therefore, the peroxide formation is one of the first reaction systems which exhibits varying non-adiabaticity and efficiencies during the reaction. Non-adiabatic calculations based on model Hamiltonians and density functional theory support the picture of chemicurrent generation and explain the rapid injection of hot hole states by an intramolecular motion, i.e., the expansion of the oxygen molecule on the timescale of a quarter of a vibrational period.

  12. Surface texture metrology for high precision surfaces

    DEFF Research Database (Denmark)

    Hansen, Hans Nørgaard; Gasparin, Stefania; Tosello, Guido


    This paper introduces some of the challenges related to surface texture measurement of high precision surfaces. The paper is presenting two case studies related to polished tool surfaces and micro part surfaces. In both cases measuring instrumentation, measurement procedure and the measurement re...

  13. Monitoring the kinetic evolution of self-assembled SiGe islands grown by Ge surface thermal diffusion from a local source (United States)

    Vanacore, G. M.; Zani, M.; Bollani, M.; Bonera, E.; Nicotra, G.; Osmond, J.; Capellini, Giovanni; Isella, G.; Tagliaferri, A.


    In this paper we experimentally study the growth of self-assembled SiGe islands formed on Si(001) by exploiting the thermally activated surface diffusion of Ge atoms from a local Ge source stripe in the temperature range 600-700 °C. This new growth strategy allows us to vary continuously the Ge coverage from 8 to 0 monolayers as the distance from the source increases, and thus enables the investigation of the island growth over a wide range of dynamical regimes at the same time, providing a unique birds eye view of the factors governing the growth process and the dominant mechanism for the mass collection by a critical nucleus. Our results give experimental evidence that the nucleation process evolves within a diffusion limited regime. At a given annealing temperature, we find that the nucleation density depends only on the kinetics of the Ge surface diffusion resulting in a universal scaling distribution depending only on the Ge coverage. An analytical model is able to reproduce quantitatively the trend of the island density. Following the nucleation, the growth process appears to be driven mainly by short-range interactions between an island and the atoms diffusing within its vicinities. The islands volume distribution is, in fact, well described in the whole range of parameters by the Mulheran’s capture zone model. The complex growth mechanism leads to a strong intermixing of Si and Ge within the island volume. Our growth strategy allows us to directly investigate the correlation between the Si incorporation and the Ge coverage in the same experimental conditions: higher intermixing is found for lower Ge coverage. This confirms that, besides the Ge gathering from the surface, also the Si incorporation from the substrate is driven by the diffusion kinetics, thus imposing a strict constraint on the initial Ge coverage, its diffusion properties and the final island volume

  14. On surface approximation using developable surfaces

    DEFF Research Database (Denmark)

    Chen, H. Y.; Lee, I. K.; Leopoldseder, S.


    We introduce a method for approximating a given surface by a developable surface. It will be either a G_1 surface consisting of pieces of cones or cylinders of revolution or a G_r NURBS developable surface. Our algorithm will also deal properly with the problems of reverse engineering and produce...... robust approximation of given scattered data. The presented technique can be applied in computer aided manufacturing, e.g. in shipbuilding....

  15. On surface approximation using developable surfaces

    DEFF Research Database (Denmark)

    Chen, H. Y.; Lee, I. K.; Leopoldseder, s.


    We introduce a method for approximating a given surface by a developable surface. It will be either a G(1) surface consisting of pieces of cones or cylinders of revolution or a G(r) NURBS developable surface. Our algorithm will also deal properly with the problems of reverse engineering and produce...... robust approximation of given scattered data. The presented technique can be applied in computer aided manufacturing, e.g. in shipbuilding. (C) 1999 Academic Press....

  16. Parametrization of translational surfaces


    Perez-Diaz, Sonia; Shen, Liyong


    The algebraic translational surface is a typical modeling surface in computer aided design and architecture industry. In this paper, we give a necessary and sufficient condition for that algebraic surface having a standard parametric representation and our proof is constructive. If the given algebraic surface is translational, then we can compute a standard parametric representation for the surface.

  17. Designing Superoleophobic Surfaces (Postprint)

    National Research Council Canada - National Science Library

    Tuteja, Anish; Choi, Wonjae; Ma, Minglin; Rutledge, Gregory C; McKinley, Gareth H; Cohen, Robert E; Mazzella, Sarah A; Mabry, Joseph M


    .... However, superoleophobic surfaces - those that display contact angles greater than 150 degrees with organic liquids having appreciably lower surface tensions than that of water - are extremely rare...

  18. Characterization of solid surfaces

    National Research Council Canada - National Science Library

    Kane, Philip F; Larrabee, Graydon B


    .... A comprehensive review of surface analysis, this important volume surveys both principles and techniques of surface characterization, describes instrumentation, and suggests the course of future research...

  19. Open algebraic surfaces

    CERN Document Server

    Miyanishi, Masayoshi


    Open algebraic surfaces are a synonym for algebraic surfaces that are not necessarily complete. An open algebraic surface is understood as a Zariski open set of a projective algebraic surface. There is a long history of research on projective algebraic surfaces, and there exists a beautiful Enriques-Kodaira classification of such surfaces. The research accumulated by Ramanujan, Abhyankar, Moh, and Nagata and others has established a classification theory of open algebraic surfaces comparable to the Enriques-Kodaira theory. This research provides powerful methods to study the geometry and topology of open algebraic surfaces. The theory of open algebraic surfaces is applicable not only to algebraic geometry, but also to other fields, such as commutative algebra, invariant theory, and singularities. This book contains a comprehensive account of the theory of open algebraic surfaces, as well as several applications, in particular to the study of affine surfaces. Prerequisite to understanding the text is a basic b...

  20. PREFACE: Fermi surface analysis using surface methods (United States)

    Michel, E. G.


    The Fermi surface of a crystalline solid represents a paradigm of quantum solid state physics: its shape is dictated by quantum mechanics, by the Fermi-Dirac statistics for electrons and by the character of Bloch states in solids. Most physical observables depend in one or other way on the shape of the Fermi surface. Due these reasons, the Fermi surface of solids has been investigated since more than 50 years using different techniques, the most important ones being the de Haas-van Alphen effect and Compton scattering. These techniques probe very precisely the Fermi surface of crystalline solids, but surface sensitive techniques are advantageous whenever no large single-crystalline samples are available, if the Brillouin zone is small or if the surface is significantly modified. In the case of low-dimensional materials, only surface sensitive techniques can be used to analyze the Fermi surface. Angle-resolved photoemission is the most powerful surface technique able to probe the Fermi surface of a solid or a surface. Also scanning tunnelling microscopy provides information on the Fermi surface, under favourable conditions. This special section presents a collection of nine invited review articles on the application of these two techniques to the study of the Fermi surface. The first paper by Kurtz reviews some general aspects on the measurement of a Fermi surface using photoemission. The next three articles deal with the Fermi surface of bulk materials. The case of a charge density wave material, where the Fermi surface is expected to play a crucial role in the stability of a particular phase, is considered in the paper by Aebi. Takahashi analyzes the electronic structure and Fermi surface of boride superconductors. Finally, Ding presents a study on how doping affects the Fermi surface of cobaltates and its relationship with other properties of these materials. The next four articles consider different examples of the application of angle-resolved photoemission to

  1. X-ray diffraction and surface acoustic wave analysis of BST/Pt/TiO{sub 2}/SiO{sub 2}/Si thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mseddi, Souhir; Hedi Ben Ghozlen, Mohamed [Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, Universite de Sfax, 3018 Sfax (Tunisia); Njeh, Anouar [Unite de Physique, Informatique et Matematiques, Faculte des Sciences de Gafsa, Universite de Gafsa, 2112 Gafsa (Tunisia); Schneider, Dieter [Fraunhofer-Institut fuer Material- und Strahltechnologie, Winterbergstrasse 28, 1277 Dresden (Germany); Fuess, Hartmut [Institute of Materials Science, University of Technology, Petersenstr.23, 64287 Darmstadt (Germany)


    High dielectric constant and electrostriction property of (Ba, Sr)Ti0{sub 3} (BST) thin films result in an increasing interest for dielectric devices and microwave acoustic resonator. Barium strontium titanate (Ba{sub 0.645}Sr{sub 0.355}TiO{sub 3}) films of about 300 nm thickness are grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrates by rf magnetron sputtering deposition techniques. X-ray diffraction is applied for the microstructural characterization. The BST films exhibit a cubic perovskite structure with a dense and smooth surface. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in the BST films. Young's modulus E and the Poisson ratio {nu} of TiO{sub 2,} Pt and BST films in different propagation directions are derived from the measured dispersion curves. Estimation of BST elastics constants are served in SAW studies. Impact of stratification process on SAW, propagating along [100] and [110] directions of silicon substrate, has been interpreted on the basis of ordinary differential equation (ODE) and stiffness matrix method (SMM). A good agreement is observed between experimental and calculated dispersion curves. The performed calculations are strongly related to the implemented crystallographic data of each layer. Dispersion curves are found to be sensitive to the SAW propagation direction and the stratification process for the explored frequency ranges 50-250 MHz, even though it corresponds to a wave length clearly higher than the whole films thickness.

  2. Surfaces with Natural Ridges

    DEFF Research Database (Denmark)

    Brander, David; Markvorsen, Steen


    We discuss surfaces with singularities, both in mathematics and in the real world. For many types of mathematical surface, singularities are natural and can be regarded as part of the surface. The most emblematic example is that of surfaces of constant negative Gauss curvature, all of which...

  3. Covalent Surface Modification of Oxide Surfaces

    NARCIS (Netherlands)

    Pujari, S.P.; Scheres, L.M.W.; Marcelis, A.T.M.; Zuilhof, H.


    The modification of surfaces by the deposition of a robust overlayer provides an excellent handle with which to tune the properties of a bulk substrate to those of interest. Such control over the surface properties becomes increasingly important with the continuing efforts at down-sizing the active


    NARCIS (Netherlands)



    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies.

  5. Mechanics of active surfaces (United States)

    Salbreux, Guillaume; Jülicher, Frank


    We derive a fully covariant theory of the mechanics of active surfaces. This theory provides a framework for the study of active biological or chemical processes at surfaces, such as the cell cortex, the mechanics of epithelial tissues, or reconstituted active systems on surfaces. We introduce forces and torques acting on a surface, and derive the associated force balance conditions. We show that surfaces with in-plane rotational symmetry can have broken up-down, chiral, or planar-chiral symmetry. We discuss the rate of entropy production in the surface and write linear constitutive relations that satisfy the Onsager relations. We show that the bending modulus, the spontaneous curvature, and the surface tension of a passive surface are renormalized by active terms. Finally, we identify active terms which are not found in a passive theory and discuss examples of shape instabilities that are related to active processes in the surface.

  6. Computer aided surface representation

    Energy Technology Data Exchange (ETDEWEB)

    Barnhill, R E


    The aims of this research are the creation of new surface forms and the determination of geometric and physical properties of surfaces. The full sweep from constructive mathematics through the implementation of algorithms and the interactive computer graphics display of surfaces is utilized. Both three-dimensional and multi- dimensional surfaces are considered. Particular emphasis is given to the scientific computing solution of Department of Energy problems. The methods that we have developed and that we are proposing to develop allow applications such as: Producing smooth contour maps from measured data, such as weather maps. Modeling the heat distribution inside a furnace from sample measurements. Terrain modeling based on satellite pictures. The investigation of new surface forms includes the topics of triangular interpolants, multivariate interpolation, surfaces defined on surfaces and monotone and/or convex surfaces. The geometric and physical properties considered include contours, the intersection of surfaces, curvatures as a interrogation tool, and numerical integration.

  7. Reactions at Solid Surfaces

    CERN Document Server

    Ertl, Gerhard


    Expanding on the ideas first presented in Gerhard Ertl's acclaimed Baker Lectures at Cornell University, Reactions at Solid Surfaces comprises an authoritative, self-contained, book-length introduction to surface reactions for both professional chemists and students alike. Outlining our present understanding of the fundamental processes underlying reactions at solid surfaces, the book provides the reader with a complete view of how chemistry works at surfaces, and how to understand and probe the dynamics of surface reactions. Comparing traditional surface probes with more modern ones, and brin

  8. Demonstration of Surface Tension. (United States)

    Rosenthal, Andrew J.


    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  9. Advanced Surface Technology

    DEFF Research Database (Denmark)

    Møller, Per; Nielsen, Lars Pleht

    of the components. It covers everything from biocompatible surfaces of IR absorbent or reflective surfaces to surfaces with specific properties within low friction, hardness, corrosion, colors, etc. The book includes more than 400 pages detailing virtually all analysis methods for examining at surfaces.......This new significant book on advanced modern surface technology in all its variations, is aimed at both teaching at engineering schools and practical application in industry. The work covers all the significant aspects of modern surface technology and also describes how new advanced techniques make...... it possible to examine surfaces all the way down to their atomic layers and also to perform realistic durability tests. The many surface techniques are described in clear and simple language, and the book is richly illustrated with detailed drawings and photos. It also deals with replacing environmentally...

  10. Smooth polyhedral surfaces

    KAUST Repository

    Günther, Felix


    Polyhedral surfaces are fundamental objects in architectural geometry and industrial design. Whereas closeness of a given mesh to a smooth reference surface and its suitability for numerical simulations were already studied extensively, the aim of our work is to find and to discuss suitable assessments of smoothness of polyhedral surfaces that only take the geometry of the polyhedral surface itself into account. Motivated by analogies to classical differential geometry, we propose a theory of smoothness of polyhedral surfaces including suitable notions of normal vectors, tangent planes, asymptotic directions, and parabolic curves that are invariant under projective transformations. It is remarkable that seemingly mild conditions significantly limit the shapes of faces of a smooth polyhedral surface. Besides being of theoretical interest, we believe that smoothness of polyhedral surfaces is of interest in the architectural context, where vertices and edges of polyhedral surfaces are highly visible.

  11. Apollo Surface Panoramas (United States)

    National Aeronautics and Space Administration — Apollo Surface Panoramas is a digital library of photographic panoramas that the Apollo astronauts took while exploring the Moon's surface. These images provide a...

  12. Integrated Surface Dataset (Global) (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Integrated Surface (ISD) Dataset (ISD) is composed of worldwide surface weather observations from over 35,000 stations, though the best spatial coverage is...

  13. Photoactivated surface grafting from PVDF surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Berthelot, Thomas, E-mail: [Chemistry of Surfaces and Interfaces, CEA Saclay, DSM/IRAMIS/SPCSI, F-91191, Gif-sur-Yvette Cedex (France); Le, Xuan Tuan; Jegou, Pascale; Viel, Pascal [Chemistry of Surfaces and Interfaces, CEA Saclay, DSM/IRAMIS/SPCSI, F-91191, Gif-sur-Yvette Cedex (France); Boizot, Bruno [Laboratory of Irradiated Solids UMR 7642 CEA/CNRS/Ecole Polytechnique, CEA-DSM/IRAMIS LSI, Ecole Polytechnique, F-91128, Palaiseau Cedex (France); Baudin, Cecile; Palacin, Serge [Chemistry of Surfaces and Interfaces, CEA Saclay, DSM/IRAMIS/SPCSI, F-91191, Gif-sur-Yvette Cedex (France)


    Economic and easy methods to tune surface properties of polymers as Poly(vinylidene fluoride) (PVDF) without altering bulk properties are of major interest for different applications as biotechnological devices, medical implant device... UV irradiation appears as one of the simplest, easy and safe method to modify surface properties. In the case of self-initiated grafting, it is generally assumed that the pre-treatment of the PVDF surface with UV irradiation can yield alkyl and per-oxy radicals originating from breaking bonds and capable of initiating the subsequent surface grafting polymerizations. Surprisingly, the present work shows that it is possible to obtain polymer grafting using low energetic UV-A irradiation (3.1-3.9 eV) without breaking PVDF bonds. An EPR study has been performed in order to investigate the nature of involved species. The ability of the activated PVDF surface to graft different kinds of hydrophilic monomers using the initiated surface polymerization method has been tested and discussed on the basis of ATR FT-IR, XPS and NMR HRMAS results.

  14. On purely real surfaces in Kaehler surfaces and Lorentz surfaces in Lorentzian Kaehler surfaces


    Chen, Bang-Yen


    An immersion $\\phi \\colon M \\to \\tilde M$ of a manifold $M$ into an indefinite Kaehler manifold $\\tilde M$ is called purely real if the almost complex structure $J$ on $\\tilde M$ carries the tangent bundle of $M$ into a transversal bundle. In this article we survey some recent results on purely real surfaces in Kaehler surfaces as well as on Lorentz surfaces in Lorentzian Kaehler surfaces.

  15. Biomaterials surface science

    CERN Document Server

    Taubert, Andreas; Rodriguez-Cabello, José Carlos


    The book provides an overview of the highly interdisciplinary field of surface science in the context of biological and biomedical applications. The covered topics range from micro- and nanostructuring for imparting functionality in a top-down manner to the bottom-up fabrication of gradient surfaces by self-assembly, from interfaces between biomaterials and living matter to smart, stimuli-responsive surfaces, and from cell and surface mechanics to the elucidation of cell-chip interactions in biomedical devices.

  16. Surface phenomena in elasticity (United States)

    Zak, M.


    Problems of elasticity associated with the behavior of free surfaces of elastic bodies are reviewed with particular reference to the propagation of characteristic waves and the criteria of wrinkling of free surfaces. All transformations are given for the case when a free surface of an elastic body is streamlined by the flow of inviscid fluid. The wrinkling phenomenon is illustrated by example.

  17. Sulfide Mineral Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rosso, Kevin M.; Vaughan, David J.


    The past twenty years or so have seen dramatic development of the experimental and theoretical tools available to study the surfaces of solids at the molecular (?atomic resolution?) scale. On the experimental side, two areas of development well illustrate these advances. The first concerns the high intensity photon sources associated with synchrotron radiation; these have both greatly improved the surface sensitivity and spatial resolution of already established surface spectroscopic and diffraction methods, and enabled the development of new methods for studying surfaces. The second centers on the scanning probe microscopy (SPM) techniques initially developed in the 1980's with the first scanning tunneling microscope (STM) and atomic force microscope (AFM) experiments. The direct 'observation' of individual atoms at surfaces made possible with these methods has truly revolutionized surface science. On the theoretical side, the availability of high performance computers coupled with advances in computational modeling has provided powerful new tools to complement the advances in experiment. Particularly important have been the quantum mechanics based computational approaches such as density functional theory (DFT), which can now be easily used to calculate the equilibrium crystal structures of solids and surfaces from first principles, and to provide insights into their electronic structure. In this chapter, we review current knowledge of sulfide mineral surfaces, beginning with an overview of the principles relevant to the study of the surfaces of all crystalline solids. This includes the thermodynamics of surfaces, the atomic structure of surfaces (surface crystallography and structural stability, adjustments of atoms at the surface through relaxation or reconstruction, surface defects) and the electronic structure of surfaces. We then discuss examples where specific crystal surfaces have been studied, with the main sulfide minerals organized by

  18. Surface for dummies

    CERN Document Server

    Rathbone, Andy


    Make Microsoft's Surface work-and play-just the way you want it to Microsoft's Surface tablet has the features and personality you're looking for, with a robust environment for business computing that doesn't skimp on fun. Surface for Dummies, 2nd Edition explains how Windows 8.1 Pro and Windows RT differ, and helps you decide which Surface model is best for you. Step by step, this book walks you through both the hardware and software features of the Surface, including the touch cover and type cover, Windows RT and Windows 8.1 Pro operating systems, and the coveted Office Home & Student 2013 s

  19. Approximation by Cylinder Surfaces

    DEFF Research Database (Denmark)

    Randrup, Thomas


    We present a new method for approximation of a given surface by a cylinder surface. It is a constructive geometric method, leading to a monorail representation of the cylinder surface. By use of a weighted Gaussian image of the given surface, we determine a projection plane. In the orthogonal...... projection of the surface onto this plane, a reference curve is determined by use of methods for thinning of binary images. Finally, the cylinder surface is constructed as follows: the directrix of the cylinder surface is determined by a least squares method minimizing the distance to the points...... in the projection within a tolerance given by the reference curve, and the rulings are lines perpendicular to the projection plane. Application of the method in ship design is given....


    Energy Technology Data Exchange (ETDEWEB)



    During this year we performed two major projects: I. We developed a detailed theoretical model which complements our experiments on surface DNA electrophoresis. We found that it was possible to enhance the separation of DNA chains by imposing a chemical nanoscale pattern on the surface. This approach utilized the surface interaction effect of the DNA chains with the substrate and is a refinement to our previous method in which DNA chains were separated on homogeneous flat surfaces. By introducing the nano-patterns on the surface, the conformational changes of DNA chains of different lengths can be amplified, which results in the different friction strengths with the substrate surface. Our results also show that, when compared to the DNA electrophoresis performed on homogeneous flat surfaces, nanopatterned surfaces offer a larger window in choosing different surface interactions to achieve separation. II. In collaboration with a large international manufacturer of skin care products we also embarked on a project involving photo toxicity of titanium dioxide nanoparticles, which are a key ingredient in sunscreen and cosmetic lotions. The results clearly implicated the nanoparticles in catalyzing damage to chromosomal DNA. We then used this knowledge to develop a polymer/anti-oxidant coating which prevented the photocatalytic reaction on DNA while still retaining the UV absorptive properties of the nanoparticles. The standard gel electrophoresis was not sufficient in determining the extent of the DNA damage. The conclusions of this study were based predominantly on analysis obtained with the surface electrophoresis method.

  1. Ruled Laguerre minimal surfaces

    KAUST Repository

    Skopenkov, Mikhail


    A Laguerre minimal surface is an immersed surface in ℝ 3 being an extremal of the functional ∫ (H 2/K-1)dA. In the present paper, we prove that the only ruled Laguerre minimal surfaces are up to isometry the surfaces ℝ (φλ) = (Aφ, Bφ, Cφ + D cos 2φ) + λ(sin φ, cos φ, 0), where A,B,C,D ε ℝ are fixed. To achieve invariance under Laguerre transformations, we also derive all Laguerre minimal surfaces that are enveloped by a family of cones. The methodology is based on the isotropic model of Laguerre geometry. In this model a Laguerre minimal surface enveloped by a family of cones corresponds to a graph of a biharmonic function carrying a family of isotropic circles. We classify such functions by showing that the top view of the family of circles is a pencil. © 2011 Springer-Verlag.

  2. Mirror reactor surface study

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, A. L.; Damm, C. C.; Futch, A. H.; Hiskes, J. R.; Meisenheimer, R. G.; Moir, R. W.; Simonen, T. C.; Stallard, B. W.; Taylor, C. E.


    A general survey is presented of surface-related phenomena associated with the following mirror reactor elements: plasma first wall, ion sources, neutral beams, director converters, vacuum systems, and plasma diagnostics. A discussion of surface phenomena in possible abnormal reactor operation is included. Several studies which appear to merit immediate attention and which are essential to the development of mirror reactors are abstracted from the list of recommended areas for surface work. The appendix contains a discussion of the fundamentals of particle/surface interactions. The interactions surveyed are backscattering, thermal desorption, sputtering, diffusion, particle ranges in solids, and surface spectroscopic methods. A bibliography lists references in a number of categories pertinent to mirror reactors. Several complete published and unpublished reports on surface aspects of current mirror plasma experiments and reactor developments are also included.

  3. Hydrodynamic Vortex on Surfaces (United States)

    Ragazzo, Clodoaldo Grotta; de Barros Viglioni, Humberto Henrique


    The equations of motion for a system of point vortices on an oriented Riemannian surface of finite topological type are presented. The equations are obtained from a Green's function on the surface. The uniqueness of the Green's function is established under hydrodynamic conditions at the surface's boundaries and ends. The hydrodynamic force on a point vortex is computed using a new weak formulation of Euler's equation adapted to the point vortex context. An analogy between the hydrodynamic force on a massive point vortex and the electromagnetic force on a massive electric charge is presented as well as the equations of motion for massive vortices. Any noncompact Riemann surface admits a unique Riemannian metric such that a single vortex in the surface does not move ("Steady Vortex Metric"). Some examples of surfaces with steady vortex metric isometrically embedded in R^3 are presented.

  4. Designing bioinspired superoleophobic surfaces

    Directory of Open Access Journals (Sweden)

    Philip S. Brown


    Full Text Available Nature provides a range of functional surfaces, for example, water-repellent or superhydrophobic surfaces, most common among them the lotus leaf. While water-repellency is widespread in nature, oil-repellency is typically limited to surfaces submerged in water, such as fish scales. To achieve oleophobicity in air, inspiration must be taken from natural structures and chemistries that are not readily available in nature need to be introduced. Researchers usually turn to fluorinated materials to provide the low surface energy that, when combined with bioinspired surface topography, is the key to unlocking oil-repellency. This review presents the state-of-the-art in the fabrication of superoleophobic surfaces.

  5. Conversion electron surface imaging

    CERN Document Server

    Irwin, G M; Wehner, A


    A method of imaging the Moessbauer absorption over the surface of a sample based on counting conversion electrons emitted from the surface following resonant absorption of gamma radiation is described. This Conversion Electron Surface Imaging (CESI) method is somewhat analogous to Magnetic Resonance Imaging (MRI), particularly chemical shift imaging, and similar tomographic reconstruction techniques are involved in extracting the image. The theory behind the technique and a prototype device is described, as well as the results of proof-of-principle experiments which demonstrate the function of the device. Eventually this same prototype device will be part of a system to determine the spatial variation of the Moessbauer spectrum over the surface of a sample. Applications include imaging of variations of surface properties of steels and other iron containing alloys, as well as other surfaces over which sup 5 sup 7 Fe has been deposited.

  6. Laser-surface interactions

    CERN Document Server

    Ganeev, Rashid A


    This book is about the interaction of laser radiation with various surfaces at variable parameters of radiation. As a basic principle of classification we chose the energetic or intensity level of interaction of laser radiation with the surfaces. These two characteristics of laser radiation are the most important parameters defining entire spectrum of the processes occurring on the surfaces during interaction with electromagnetic waves. This is a first book containing a whole spectrum of the laser-surface interactions distinguished by the ranges of used laser intensity. It combines the surface response starting from extremely weak laser intensities (~1 W cm-2) up to the relativistic intensities (~1020 W cm-2 and higher). The book provides the basic information about lasers and acquaints the reader with both common applications of laser-surface interactions (laser-related printers, scanners, barcode readers, discs, material processing, military, holography, medicine, etc) and unusual uses of the processes on t...


    Directory of Open Access Journals (Sweden)



    Full Text Available Surface characterization means splitting the surface geometry into basic components based usually on some functional requirement. These components can have different shapes, scales of size, distribution in space and can be constrained by multiple boundaries in height and position. The measurement can influence the importance of a parameter or feature. This paper presents the main features that need to be considered when a surface is analyzed, especially the roughness and the waviness.

  8. Landsat surface reflectance data (United States)



    Landsat satellite data have been produced, archived, and distributed by the U.S. Geological Survey since 1972. Users rely on these data for historical study of land surface change and require consistent radiometric data processed to the highest science standards. In support of the guidelines established through the Global Climate Observing System, the U.S. Geological Survey has embarked on production of higher-level Landsat data products to support land surface change studies. One such product is Landsat surface reflectance.

  9. Anatomically Correct Surface Recovery

    DEFF Research Database (Denmark)

    Jensen, Rasmus Ramsbøl; Nielsen, Jannik Boll; Larsen, Rasmus


    We present a method for 3D surface recovery in partial surface scans. The method is based on an Active Shape Model, which is used to predict missing data. The model is constructed using a bootstrap framework, where an initially small collection of hand-annotated samples is used to fit......-of-the-art surface reconstruction algorithm, the presented method gives matching prediction results for the synthetic evaluation samples and superior results for the direct scanner data....

  10. Impact of surface chemistry (United States)

    Somorjai, Gabor A.; Li, Yimin


    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized. PMID:20880833

  11. Encyclopedia of analytical surfaces

    CERN Document Server

    Krivoshapko, S N


    This encyclopedia presents an all-embracing collection of analytical surface classes. It provides concise definitions  and description for more than 500 surfaces and categorizes them in 38 classes of analytical surfaces. All classes are cross references to the original literature in an excellent bibliography. The encyclopedia is of particular interest to structural and civil engineers and serves as valuable reference for mathematicians.

  12. Surface chemistry essentials

    CERN Document Server

    Birdi, K S


    Surface chemistry plays an important role in everyday life, as the basis for many phenomena as well as technological applications. Common examples range from soap bubbles, foam, and raindrops to cosmetics, paint, adhesives, and pharmaceuticals. Additional areas that rely on surface chemistry include modern nanotechnology, medical diagnostics, and drug delivery. There is extensive literature on this subject, but most chemistry books only devote one or two chapters to it. Surface Chemistry Essentials fills a need for a reference that brings together the fundamental aspects of surface chemistry w

  13. Surface science an introduction

    CERN Document Server

    Hudson, John


    The whole field of surface science is covered in this work. Starting with a description of the structure and thermodynamics of clean surfaces, the book goes on to discuss kinetic theory of gases and molecular beam formation. This is followed by a largesection on gas-surface interactions, and another major section on energetic particle-surface interactions. The final chapter provides the background to crystal nucleation and growth. The approach adopted is interdisciplinary and slanted towards theexperimental side, with practical analytical techniques being used to illustrate general princi

  14. Medical facial surface scanner (United States)

    Vannier, Michael W.; Bhatia, Gulab H.; Commean, Paul K.; Pilgram, Thomas K.; Brunsden, Barry S.


    Optical, non-contact three-dimensional range surface digitizers are employed in the 360-degree examination of object surfaces, especially the heads and faces of individuals. The resultant 3- D surface data is suitable for computer graphics display and manipulation, for numerically controlled object replications, or for further processing such as surface measurement extraction. We employed a scanner with a basic active sensor element consisting of a synchronized pattern projector employing flashtubes that illuminate a surface, with a CID camera to detect, digitize, and transmit the sequence of 24 images (per camera) to a digital image processor for surface triangulation, calibration, and fusion into a single surface description of the headform. A major feature of this unit is its use of multiple (typically 6) stationary active sensor elements, with efficient calibration algorithms that achieve nearly seamless superposition of overlapping surface segments seen by individual cameras. The result is accurate and complete coverage of complex contoured surfaces. Application of this system to digitization of the human head in the planning and evaluation of facial plastic surgery is presented.

  15. Pseudospherical surfaces with singularities

    DEFF Research Database (Denmark)

    Brander, David


    We study a generalization of constant Gauss curvature −1 surfaces in Euclidean 3-space, based on Lorentzian harmonic maps, that we call pseudospherical frontals. We analyse the singularities of these surfaces, dividing them into those of characteristic and non-characteristic type. We give methods...

  16. Chapter 8:Surface Characterization (United States)

    Mandla A. Tshabalala; Joseph Jakes; Mark R. VanLandingham; Shaoxia Wang; Jouko. Peltonen


    Surface properties of wood play an important role when wood is used or processed into different commodities such as siding, joinery, textiles, paper, sorption media, or wood composites. Thus, for example, the quality and durability of a wood coating are determined by the surface properties of the wood and the coating. The same is true for wood composites where the...

  17. Surface nanobubbles and nanodroplets

    NARCIS (Netherlands)

    Lohse, Detlef; Zhang, Xuehua


    Surface nanobubbles are nanoscopic gaseous domains on immersed substrates which can survive for days. They were first speculated to exist about 20 years ago, based on stepwise features in force curves between two hydrophobic surfaces, eventually leading to the first atomic force microscopy (AFM)

  18. Modifying Surfaces with Light. (United States)

    Koberstein, Jeff; Carrol, Greg; Pan, Feng; Wang, Peng; Turro, Nicholas


    The ability to locate particular functional groups at surfaces is an enabling aspect of many important technologies. Unfortunately, high energy functional groups are not thermodynamically stable at the surface of polymers and other low surface tension materials. We show that this difficulty can be overcome through the synthesis of surface active block copolymers and self-assembled monolayers that contain photoactive functional groups. Photoactive functional groups are protected during the synthesis step, but can be deprotected upon exposure to light. To accomplish this task we borrow from photoresist technology and employ photoacid generators to deprotect carboxylic acid groups delivered to a surface upon exposure to light. Since all modifications are accomplished with light, direct micropatterning of surface functional groups is possible simply by exposure through a mask. The technique is thus a simple, direct alternative to other patterning techniques such as stamping. We also demonstrate that polymers and carbohydrates can be photografted to a surface using photoactive groups that are capable of hydrogen abstraction. Applications that are demonstrated include prevention of thin film dewetting, general surface functionalization, micropatterning of functional groups, polymers and biopolymers, and the creation of the first covalently bound carbohydrate microarrays. This work is funded by grants from the Polymer Program of the National Science Foundation Division of Materials Research and the U.S. Army Research Office.

  19. Microbubble Surface Modes

    NARCIS (Netherlands)

    Versluis, Michel; Palanchon, P.; Goertz, D.; van der Meer, S.M.; Chin, C.T.; Lohse, Detlef; de Jong, N.


    We have investigated surface vibrations generated by ultrasound excitation of individual unencapsulated micron-sized bubbles. In addition, we present surface modes (n=2 and 3) observed for phospholipid-coated ultrasound contrast agents excited through excitation of radial modes at frequencies

  20. Solar absorption surface panel (United States)

    Santala, Teuvo J.


    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  1. Surface enhanced Raman scattering

    CERN Document Server

    Furtak, Thomas


    In the course of the development of surface science, advances have been identified with the introduction of new diagnostic probes for analytical characterization of the adsorbates and microscopic structure of surfaces and interfaces. Among the most recently de­ veloped techniques, and one around which a storm of controversy has developed, is what has now been earmarked as surface enhanced Raman scattering (SERS). Within this phenomenon, molecules adsorbed onto metal surfaces under certain conditions exhibit an anomalously large interaction cross section for the Raman effect. This makes it possible to observe the detailed vibrational signature of the adsorbate in the ambient phase with an energy resolution much higher than that which is presently available in electron energy loss spectroscopy and when the surface is in contact with a much larger amount of material than that which can be tolerated in infrared absorption experiments. The ability to perform vibrational spectroscopy under these conditions would l...

  2. Defects at oxide surfaces

    CERN Document Server

    Thornton, Geoff


    This book presents the basics and characterization of defects at oxide surfaces. It provides a state-of-the-art review of the field, containing information to the various types of surface defects, describes analytical methods to study defects, their chemical activity and the catalytic reactivity of oxides. Numerical simulations of defective structures complete the picture developed. Defects on planar surfaces form the focus of much of the book, although the investigation of powder samples also form an important part. The experimental study of planar surfaces opens the possibility of applying the large armoury of techniques that have been developed over the last half-century to study surfaces in ultra-high vacuum. This enables the acquisition of atomic level data under well-controlled conditions, providing a stringent test of theoretical methods. The latter can then be more reliably applied to systems such as nanoparticles for which accurate methods of characterization of structure and electronic properties ha...

  3. Advanced Surface Technology

    DEFF Research Database (Denmark)

    Møller, Per; Nielsen, Lars Pleht

    it possible to examine surfaces all the way down to their atomic layers and also to perform realistic durability tests. The many surface techniques are described in clear and simple language, and the book is richly illustrated with detailed drawings and photos. It also deals with replacing environmentally......, nitriding, carbonitriding, and many other lesser-known thermochemical processes used for solving technological problems. The book is richly illustrated with pictures and figures showing how the technology creates new innovative solutions for industry and how surfaces are becoming integral to the function......This new significant book on advanced modern surface technology in all its variations, is aimed at both teaching at engineering schools and practical application in industry. The work covers all the significant aspects of modern surface technology and also describes how new advanced techniques make...

  4. Real estate surfaces appraisal

    Directory of Open Access Journals (Sweden)

    Marina Ciuna


    Full Text Available In the appraisal of the market value of the properties are applied two important surface indexes: the market surface ratio of the secondary surfaces and the ratio of the site value to total value (allocation method. The measure of both these indexes can be revealed difficult: the data collection of the surface trade ratio in the market can get different results and in practice often the valuer refolds on the fixed coefficients brought in the handbooks and in the circulars of the public administration; the appraisal of the ratio of the site, especially in the central zones and for ancient buildings, where besides the incidence is higher, is developed extrapolating the ratios from the peripheral zones for new building or falling back on the publications of real estate sector.For the market comparison methods are proposed a series of test of surface trade ratio and land value ratio to foresee the effect on the appraisal result.

  5. Rough Surface Contact

    Directory of Open Access Journals (Sweden)

    T Nguyen


    Full Text Available This paper studies the contact of general rough curved surfaces having nearly identical geometries, assuming the contact at each differential area obeys the model proposed by Greenwood and Williamson. In order to account for the most general gross geometry, principles of differential geometry of surface are applied. This method while requires more rigorous mathematical manipulations, the fact that it preserves the original surface geometries thus makes the modeling procedure much more intuitive. For subsequent use, differential geometry of axis-symmetric surface is considered instead of general surface (although this “general case” can be done as well in Chapter 3.1. The final formulas for contact area, load, and frictional torque are derived in Chapter 3.2.

  6. Testing of aspheric surfaces (United States)

    Tiziani, Hans J.; Reichelt, Stephan; Pruss, Christof; Rocktaeschel, M.; Hofbauer, U.


    Aspheric surfaces are becoming interesting for the reduction of elements in optical systems as well as for improving the quality of the image forming system. The fabrication process of aspheric surfaces has been improved. For optical testing of aspheric surfaces computer generated holograms (CGHs) are interesting and already used. To perform aspheric testing in the same accuracy as spherical surface testing, further improvements of the CGH-null test method are required. A new concept for testing aspheric surfaces with CGH-nulls, including a calibration of the system, will be described. To specify and verify CGH quality, systematic errors due to fabrication inaccuracies of the CGHs will be analysed. On the other hand, alternative methods that provide more flexibility but possibly less accuracy than the CGH-null technique are required. Potential alternative testing methods of aspherics will be discussed.

  7. Electrohydrodynamics near hydrophobic surfaces. (United States)

    Maduar, S R; Belyaev, A V; Lobaskin, V; Vinogradova, O I


    We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counterions of the electrostatic diffuse layer. For a hydrophobic surface with immobile charges, the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges, it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electrohydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta potential of hydrophobic surfaces.

  8. Electrokinetics on superhydrophobic surfaces. (United States)

    Papadopoulos, Periklis; Deng, Xu; Vollmer, Doris; Butt, Hans-Jürgen


    On a superhydrophobic surface a liquid is exposed to a large air-water interface. The reduced wall friction is expected to cause a higher electro-osmotic mobility. On the other hand, the low charge density of a superhydrophobic surface reduces the electro-osmotic mobility. Due to a lack of experimental data it has not been clear so far whether the reduced wall friction or the reduced charge density dominate the electrokinetic mobilities. To separate the relative contributions of electrophoresis and electro-osmosis, the mobilities of colloids on a negatively charged hydrophilic, a superhydrophobic (Cassie) and a partially hydrophilized superhydrophobic (Cassie composite) coating were measured. To vary the charge density as well as its sign with respect to those of the colloids the partially hydrophilized surfaces were coated with polyelectrolytes. We analyzed the electrokinetic mobilities of negatively charged polystyrene colloids dispersed in aqueous medium on porous hydrophilic and superhydrophobic surfaces by confocal laser scanning electron microscopy. In all cases, the external electric field was parallel to the surface. The total electrokinetic mobilities on the superhydrophobic (Cassie) and negatively charged partially hydrophilized (Cassie composite) surfaces were similar, showing that electro-osmosis is small compared to electrophoresis. The positively charged Cassie composite surfaces tend to 'trap' the colloids due to attracting electrostatic interactions and rough morphology, reducing the mobility. Thus, either the charge density of the coatings in the Cassie composite state or its slip length is too low to enhance electro-osmosis.

  9. Surface modes in physics

    CERN Document Server

    Sernelius, Bo E


    Electromagnetic surface modes are present at all surfaces and interfaces between material of different dielectric properties. These modes have very important effects on numerous physical quantities: adhesion, capillary force, step formation and crystal growth, the Casimir effect etc. They cause surface tension and wetting and they give rise to forces which are important e.g. for the stability of colloids.This book is a useful and elegant approach to the topic, showing how the concept of electromagnetic modes can be developed as a unifying theme for a range of condensed matter physics. The

  10. Surface layers of bacteria. (United States)

    Beveridge, T J; Graham, L L


    Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance of the results in terms of our perception of the makeup and function of bacterial surfaces and their interaction with the surrounding environment.

  11. Nonlinear surface electromagnetic phenomena

    CERN Document Server

    Ponath, H-E


    In recent years the physics of electromagnetic surface phenomena has developed rapidly, evolving into technologies for communications and industry, such as fiber and integrated optics. The variety of phenomena based on electromagnetism at surfaces is rich and this book was written with the aim of summarizing the available knowledge in selected areas of the field. The book contains reviews written by solid state and optical physicists on the nonlinear interaction of electromagnetic waves at and with surfaces and films. Both the physical phenomena and some potential applications are

  12. Characterisation of Functional Surfaces

    DEFF Research Database (Denmark)

    Lonardo, P.M.; De Chiffre, Leonardo; Bruzzone, A.A.


    Characterisation of surfaces is of fundamental importance to control the manufacturing process and the functional performance of the part. Many applications concern contact and tribology problems, which include friction, wear and lubrication. This paper presents the techniques and instruments...... for characterisation of surfaces, discussing their operating principles and metrological properties. A review of the conventional 2D and new 3D roughness parameters is given, considering both the current standards and new proposals for texture quantification, with a particular attention to the methods orientated...... towards a functional characterisation of surfaces....

  13. Advanced Surface Technology

    DEFF Research Database (Denmark)

    Møller, Per; Nielsen, Lars Pleht

    This new significant book on advanced modern surface technology in all its variations, is aimed at both teaching at engineering schools and practical application in industry. The work covers all the significant aspects of modern surface technology and also describes how new advanced techniques make......, nitriding, carbonitriding, and many other lesser-known thermochemical processes used for solving technological problems. The book is richly illustrated with pictures and figures showing how the technology creates new innovative solutions for industry and how surfaces are becoming integral to the function...

  14. Surface science techniques

    CERN Document Server

    Walls, JM


    This volume provides a comprehensive and up to the minute review of the techniques used to determine the nature and composition of surfaces. Originally published as a special issue of the Pergamon journal Vacuum, it comprises a carefully edited collection of chapters written by specialists in each of the techniques and includes coverage of the electron and ion spectroscopies, as well as the atom-imaging methods such as the atom probe field ion microscope and the scanning tunnelling microscope. Surface science is an important area of study since the outermost surface layers play a crucial role

  15. Localized Acoustic Surface Modes

    KAUST Repository

    Farhat, Mohamed


    We introduce the concept of localized acoustic surface modes (ASMs). We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.

  16. Architectural Knitted Surfaces

    DEFF Research Database (Denmark)

    Mossé, Aurélie


    WGSN reports from the Architectural Knitted Surfaces workshop recently held at ShenkarCollege of Engineering and Design, Tel Aviv, which offered a cutting-edge insight into interactive knitted surfaces. With the increasing role of smart textiles in architecture, the Architectural Knitted Surfaces...... workshop brought together architects and interior and textile designers to highlight recent developments in intelligent knitting. The five-day workshop was led by architects Ayelet Karmon and Mette Ramsgaard Thomsen, together with Amir Cang and Eyal Sheffer from the Knitting Laboratory, in collaboration...

  17. Water sorption, solubility and surface roughness of resin surface sealants


    Biazuz,Jaqueline; Zardo,Patrícia; Rodrigues-Junior,Sinval Adalberto


    Surface sealants have been suggested as final glaze of the surface of composite restorations. However, little is known about bulk and surface properties of these materials aiming the long-term preservation of the surface integrity of these restorations. AIM: To evaluate the water sorption, solubility and surface roughness of commercial surface sealants for restorations. METHODS: Five disc-shaped specimens 15 mm diameter X 1 mm high were made from the surface sealants Natural Glaze DFL and Per...

  18. Lunar Surface Navigation Project (United States)

    National Aeronautics and Space Administration — To support extended lunar operations, precision localization and route mapping is required for planetary EVA, manned rovers and lunar surface mobility units. A...

  19. Novel Surface Transportation Modes (United States)


    This report summarizes an initial stage investigation into current research and development of alternative modal concepts. The project goals were to gain a better understanding of novel surface transportation concepts that fall outside of the Federal...

  20. Surface Plasmon Based Spectrometer (United States)

    Wig, Andrew; Passian, Ali; Boudreaux, Philip; Ferrell, Tom


    A spectrometer that uses surface plasmon excitation in thin metal films to separate light into its component wavelengths is described. The use of surface plasmons as a dispersive medium sets this spectrometer apart from prism, grating, and interference based variants and allows for the miniaturization of this device. Theoretical and experimental results are presented for two different operation models. In the first case surface plasmon tunneling in the near field is used to provide transmission spectra of different broad band-pass, glass filters across the visible wavelength range with high stray-light rejection at low resolution as well as absorption spectra of chlorophyll extracted from a spinach leaf. The second model looks at the far field components of surface plasmon scattering.

  1. Land Surface Weather Observations (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — METAR is the international standard code format for hourly surface weather observations. The acronym roughly translates from French as Aviation Routine Weather...



    L. I. IVANKIV; O. V. DZYUPYN; Balitskii, O. A.


    This paper describes the oxygen adsorption properties on magnesium oxide surface. The results are compared with theoretical adsorption kinetics. Temperature and time dependences of adsorption mechanisms and chemiluminescence are discussed.

  3. Surface Weather Observations Monthly (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Surface Weather Observation 1001 Forms is a set of historical manuscript records for the period 1893-1948. The collection includes two very similar form types: Form...

  4. Uruguay - Surface Weather Observations (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Surface weather observation forms for 26 stations in Uruguay. Period of record 1896-2005, with two to eight observations per day. Files created through a...

  5. Iowa Bedrock Surface Elevation (United States)

    Iowa State University GIS Support and Research Facility — This Digital Elevation Model (DEM) of the bedrock surface elevation in Iowa was compiled using all available data, principally information from GEOSAM, supplemented...

  6. Surface Tension of Spacetime (United States)

    Perko, Howard


    Concepts from physical chemistry and more specifically surface tension are introduced to spacetime. Lagrangian equations of motion for membranes of curved spacetime manifold are derived. The equations of motion in spatial directions are dispersion equations and can be rearranged to Schrodinger's equation where Plank's constant is related to membrane elastic modulus. The equation of motion in the time-direction has two immediately recognizable solutions: electromagnetic waves and corpuscles. The corpuscular membrane solution can assume different genus depending on quantized amounts of surface energy. A metric tensor that relates empty flat spacetime to energetic curved spacetime is found that satisfies general relativity. Application of the surface tension to quantum electrodynamics and implications for quantum chromodynamics are discussed. Although much work remains, it is suggested that spacetime surface tension may provide a classical explanation that combines general relativity with field theories in quantum mechanics and atomic particle physics.

  7. Surface Weather Observations (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Surface Weather Observation Collection consists primarily of hourly, synoptic, daily, and monthly forms submitted to the archive by the National Weather Service...

  8. Surfaces in 4-Manifolds

    CERN Document Server

    Fintushel, R; Fintushel, Ronald; Stern, Ronald J.


    In this paper we introduce a technique, called rim surgery, which can change a smooth embedding of an orientable surface of positive genus and nonnegative self-intersection in a smooth 4-manifold while leaving the topological embedding unchanged.

  9. Mexico - Surface Weather Observations (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Mexican Surface Daily Observations taken at 94 observatories located throughout Mexico, beginning in 1872 and going up through 1981. The data resided on paper...

  10. Biological surface science (United States)

    Kasemo, Bengt


    Biological surface science (BioSS), as defined here is the broad interdisciplinary area where properties and processes at interfaces between synthetic materials and biological environments are investigated and biofunctional surfaces are fabricated. Six examples are used to introduce and discuss the subject: Medical implants in the human body, biosensors and biochips for diagnostics, tissue engineering, bioelectronics, artificial photosynthesis, and biomimetic materials. They are areas of varying maturity, together constituting a strong driving force for the current rapid development of BioSS. The second driving force is the purely scientific challenges and opportunities to explore the mutual interaction between biological components and surfaces. Model systems range from the unique water structures at solid surfaces and water shells around proteins and biomembranes, via amino and nucleic acids, proteins, DNA, phospholipid membranes, to cells and living tissue at surfaces. At one end of the spectrum the scientific challenge is to map out the structures, bonding, dynamics and kinetics of biomolecules at surfaces in a similar way as has been done for simple molecules during the past three decades in surface science. At the other end of the complexity spectrum one addresses how biofunctional surfaces participate in and can be designed to constructively participate in the total communication system of cells and tissue. Biofunctional surfaces call for advanced design and preparation in order to match the sophisticated (bio) recognition ability of biological systems. Specifically this requires combined topographic, chemical and visco-elastic patterns on surfaces to match proteins at the nm scale and cells at the micrometer scale. Essentially all methods of surface science are useful. High-resolution (e.g. scanning probe) microscopies, spatially resolved and high sensitivity, non-invasive optical spectroscopies, self-organizing monolayers, and nano- and microfabrication

  11. On-surface magnetochemistry


    Wäckerlin, Christian


    This thesis reports on the on-surface magnetochemistry of square-planar transition-metal complexes adsorbed on ferromagnetic substrates. Specifically, the magnetochemistry of the transition-metal ions (Mn / Fe / Co / Ni) coordinated in square-planar porphyrin / phthalocyanine ligands arranged on native and oxygen-reconstructed ferromagnetic Ni(001) / Co(001) thin-films is studied. The metal-centers in the surface-adsorbed complexes are five-fold coordinated: four coordination-bonds with the s...

  12. Surface layers of bacteria.


    Beveridge, T. J.; Graham, L L


    Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance ...

  13. Lights illuminate surfaces superluminally (United States)

    Nemiroff, Robert J.; Zhong, Qi; Lilleskov, Elias


    When a light bulb is turned on, light moves away from it at speed c, by definition. When light from this bulb illuminates a surface, however, this illumination front is not constrained to move at speed c. A simple proof is given that this illumination front always moves faster than c. Generalized, when any compact light source itself varies, this information spreads across all of the surfaces it illuminates at speeds faster than light.

  14. Multifunctional thin film surface (United States)

    Brozik, Susan M.; Harper, Jason C.; Polsky, Ronen; Wheeler, David R.; Arango, Dulce C.; Dirk, Shawn M.


    A thin film with multiple binding functionality can be prepared on an electrode surface via consecutive electroreduction of two or more aryl-onium salts with different functional groups. This versatile and simple method for forming multifunctional surfaces provides an effective means for immobilization of diverse molecules at close proximities. The multifunctional thin film has applications in bioelectronics, molecular electronics, clinical diagnostics, and chemical and biological sensing.

  15. Decorative Plasmonic Surfaces


    Chorsi, Hamid T.; Zhu, Ying; Zhang, John X. J.


    Low-profile patterned plasmonic surfaces are synergized with a broad class of silicon microstructures to greatly enhance near-field nanoscale imaging, sensing, and energy harvesting coupled with far-field free-space detection. This concept has a clear impact on several key areas of interest for the MEMS community, including but not limited to ultra-compact microsystems for sensitive detection of small number of target molecules, and surface devices for optical data storage, micro-imaging and ...

  16. Dyakonov surface waves

    DEFF Research Database (Denmark)

    Takayama, Osamu; Crasovan, Lucian Cornel; Johansen, Steffen Kjær


    The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special......, the existence of these surface waves in specific material examples is analyzed, discussing the challenge posed by their experimental observation....

  17. Surface Mediated Protein Disaggregation (United States)

    Radhakrishna, Mithun; Kumar, Sanat K.


    Preventing protein aggregation is of both biological and industrial importance. Biologically these aggregates are known to cause amyloid type diseases like Alzheimer's and Parkinson's disease. Protein aggregation leads to reduced activity of the enzymes in industrial applications. Inter-protein interactions between the hydrophobic residues of the protein are known to be the major driving force for protein aggregation. In the current paper we show how surface chemistry and curvature can be tuned to mitigate these inter-protein interactions. Our results calculated in the framework of the Hydrophobic-Polar (HP) lattice model show that, inter-protein interactions can be drastically reduced by increasing the surface hydrophobicity to a critical value corresponding to the adsorption transition of the protein. At this value of surface hydrophobicity, proteins lose inter-protein contacts to gain surface contacts and thus the surface helps in reducing the inter-protein interactions. Further, we show that the adsorption of the proteins inside hydrophobic pores of optimal sizes are most efficient both in reducing inter-protein contacts and simultaneously retaining most of the native-contacts due to strong protein-surface interactions coupled with stabilization due to the confinement. Department of Energy (Grant No DE-FG02-11ER46811).

  18. Mars Surface Environmental Issues (United States)

    Charles, John


    Planetary exploration by astronauts will require extended periods of habitation on a planet's surface, under the influence of environmental factors that are different from those of Earth and the spacecraft that delivered the crew to the planet. Human exploration of Mars, a possible near-term planetary objective, can be considered a challenging scenario. Mission scenarios currently under consideration call for surface habitation periods of from 1 to 18 months on even the earliest expeditions. Methods: Environmental issues associated with Mars exploration have been investigated by NASA and the National Space Biomedical Research Institute (NSBRI) as part of the Bioastronautics Critical Path Roadmap Project (see http :// Results: Arrival on Mars will immediately expose the crew to gravity only 38% of that at Earth's surface in possibly the first prolonged exposure to gravity other than the 1G of Earth's surface and the zero G of weightless space flight, with yet unknown effects on crew physiology. The radiation at Mars' surface is not well documented, although the planet's bulk and even its thin atmosphere may moderate the influx of galactic cosmic radiation and energetic protons from solar flares. Secondary radiation from activated components of the soil must also be considered. Ultrafine and larger respirable and nonrespirable particles in Martian dust introduced into the habitat after surface excursions may induce pulmonary inflammation exacerbated by the additive reactive and oxidizing nature of the dust. Stringent decontamination cannot eliminate mechanical and corrosive effects of the dust on pressure suits and exposed machinery. The biohazard potential of putative indigenous Martian microorganisms may be assessed by comparison with analog environments on Earth. Even in their absence, human microorganisms, if not properly controlled, can be a threat to the crew's health. Conclusions: Mars' surface offers a substantial challenge to the

  19. Surface chemistry theory and applications

    CERN Document Server

    Bikerman, J J


    Surface Chemistry Theory and Applications focuses on liquid-gas, liquid-liquid, solid-gas, solid-liquid, and solid-solid surfaces. The book first offers information on liquid-gas surfaces, including surface tension, measurement of surface tension, rate of capillarity rise, capillary attraction, bubble pressure and pore size, and surface tension and temperature. The text then ponders on liquid-liquid and solid-gas surfaces. Discussions focus on surface energy of solids, surface roughness and cleanness, adsorption of gases and vapors, adsorption hysteresis, interfacial tension, and interfacial t

  20. Anticipating land surface change. (United States)

    Streeter, Richard; Dugmore, Andrew J


    The interplay of human actions and natural processes over varied spatial and temporal scales can result in abrupt transitions between contrasting land surface states. Understanding these transitions is a key goal of sustainability science because they can represent abrupt losses of natural capital. This paper recognizes flickering between alternate land surface states in advance of threshold change and critical slowing down in advance of both threshold changes and noncritical transformation. The early warning signals we observe are rises in autocorrelation, variance, and skewness within millimeter-resolution thickness measurements of tephra layers deposited in A.D. 2010 and A.D. 2011. These signals reflect changing patterns of surface vegetation, which are known to provide early warning signals of critical transformations. They were observed toward migrating soil erosion fronts, cryoturbation limits, and expanding deflation zones, thus providing potential early warning signals of land surface change. The record of the spatial patterning of vegetation contained in contemporary tephra layers shows how proximity to land surface change could be assessed in the widespread regions affected by shallow layers of volcanic fallout (those that can be subsumed within the existing vegetation cover). This insight shows how we could use tephra layers in the stratigraphic record to identify "near misses," close encounters with thresholds that did not lead to tipping points, and thus provide additional tools for archaeology, sustainability science, and contemporary land management.

  1. Iron oxide surfaces (United States)

    Parkinson, Gareth S.


    The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

  2. Responsive acoustic surfaces

    DEFF Research Database (Denmark)

    Peters, Brady; Tamke, Martin; Nielsen, Stig Anton


    Acoustic performance is defined by the parameter of reverberation time; however, this does not capture the acoustic experience in some types of open plan spaces. As many working and learning activities now take place in open plan spaces, it is important to be able to understand and design...... for the acoustic conditions of these spaces. This paper describes an experimental research project that studied the design processes necessary to design for sound. A responsive acoustic surface was designed, fabricated and tested. This acoustic surface was designed to create specific sonic effects. The design...... was simulated using custom integrated acoustic software and also using Odeon acoustic analysis software. The research demonstrates a method for designing space- and sound-defining surfaces, defines the concept of acoustic subspace, and suggests some new parameters for defining acoustic subspaces....

  3. Surface-water surveillance

    Energy Technology Data Exchange (ETDEWEB)

    Saldi, K.A.; Dirkes, R.L.; Blanton, M.L.


    This section of the 1994 Hanford Site Environmental Report summarizes the Surface water on and near the Hanford Site is monitored to determine the potential effects of Hanford operations. Surface water at Hanford includes the Columbia River, riverbank springs, ponds located on the Hanford Site, and offsite water systems directly east and across the Columbia River from the Hanford Site, and offsite water systems directly east and across the Columbia River from the Hanford Site. Columbia River sediments are also included in this discussion. Tables 5.3.1 and 5.3.2 summarize the sampling locations, sample types, sampling frequencies, and sample analyses included in surface-water surveillance activities during 1994. Sample locations are also identified in Figure 5.3.1. This section describes the surveillance effort and summarizes the results for these aquatic environments. Detailed analytical results are reported by Bisping (1995).

  4. From analysis to surface

    DEFF Research Database (Denmark)

    Bemman, Brian; Meredith, David


    In recent years, a significant body of research has focused on developing algorithms for computing analyses of mu- sical works automatically from encodings of these works' surfaces [3,4,7,10,11]. The quality of the output of such analysis algorithms is typically evaluated by comparing it with a “......In recent years, a significant body of research has focused on developing algorithms for computing analyses of mu- sical works automatically from encodings of these works' surfaces [3,4,7,10,11]. The quality of the output of such analysis algorithms is typically evaluated by comparing...... it with a “ground truth” analysis of the same music pro- duced by a human expert (see, in particular, [5]). In this paper, we explore the problem of generating an encoding of the musical surface of a work automatically from a systematic encoding of an analysis. The ability to do this depends on one having...

  5. Magnetic surface anisotropy (United States)

    Rado, George T.


    Selected aspects of magnetic surface anisotropy are reviewed. The emphasis is on methods for deducing reliable surface anisotropy values from experiments such as ferromagnetic resonance at microwave frequencies and Brillouin scattering at optical frequencies. The methods used are the "general exchange boundary condition method" and the "effective volume anisotropy method". The essence of the former is the supplementing of the equation of motion of the magnetization with the general exchange boundary condition whereas the latter consists of using the "stratagem" of effective volume anisotropy. We find that use of the general exchange boundary condition method is not only preferable in principle but often actually necessary to prevent the prediction of wrong surface anisotropy values and to permit the prediction of some observable Brillouin shifts.

  6. Organometallic chemistry of metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Muetterties, E.L.


    The organometallic chemistry of metal surfaces is defined as a function of surface crystallography and of surface composition for a set of cyclic hydrocarbons that include benzene, toluene, cyclohexadienes, cyclohexene, cyclohexane, cyclooctatetraene, cyclooctadienes, cyclooctadiene, cycloheptatriene and cyclobutane. 12 figures.

  7. Surface Aesthetics and Analysis. (United States)

    Çakır, Barış; Öreroğlu, Ali Rıza; Daniel, Rollin K


    Surface aesthetics of an attractive nose result from certain lines, shadows, and highlights with specific proportions and breakpoints. Analysis emphasizes geometric polygons as aesthetic subunits. Evaluation of the complete nasal surface aesthetics is achieved using geometric polygons to define the existing deformity and aesthetic goals. The relationship between the dome triangles, interdomal triangle, facet polygons, and infralobular polygon are integrated to form the "diamond shape" light reflection on the nasal tip. The principles of geometric polygons allow the surgeon to analyze the deformities of the nose, define an operative plan to achieve specific goals, and select the appropriate operative technique. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Surface science techniques

    CERN Document Server

    Bracco, Gianangelo


    The book describes the experimental techniques employed to study surfaces and interfaces. The emphasis is on the experimental method. Therefore all chapters start with an introduction of the scientific problem, the theory necessary to understand how the technique works and how to understand the results. Descriptions of real experimental setups, experimental results at different systems are given to show both the strength and the limits of the technique. In a final part the new developments and possible extensions of the techniques are presented. The included techniques provide microscopic as well as macroscopic information. They cover most of the techniques used in surface science.

  9. Photochemistry on solid surfaces

    CERN Document Server

    Matsuura, T


    The latest developments in photochemistry on solid surfaces, i.e. photochemistry in heterogeneous systems, including liquid crystallines, are brought together for the first time in a single volume. Distinguished photochemists from various fields have contributed to the book which covers a number of important applications: molecular photo-devices for super-memory, photochemical vapor deposition to produce thin-layered electronic semiconducting materials, sensitive optical media, the control of photochemical reactions pathways, etc. Photochemistry on solid surfaces is now a major field and this

  10. Surface and nanomolecular catalysis

    CERN Document Server

    Richards, Ryan


    Using new instrumentation and experimental techniques that allow scientists to observe chemical reactions and molecular properties at the nanoscale, the authors of Surface and Nanomolecular Catalysis reveal new insights into the surface chemistry of catalysts and the reaction mechanisms that actually occur at a molecular level during catalysis. While each chapter contains the necessary background and explanations to stand alone, the diverse collection of chapters shows how developments from various fields each contributed to our current understanding of nanomolecular catalysis as a whole. The

  11. Solar Surface Convection

    Directory of Open Access Journals (Sweden)

    Nordlund Åke


    Full Text Available We review the properties of solar convection that are directly observable at the solar surface, and discuss the relevant underlying physics, concentrating mostly on a range of depths from the temperature minimum down to about 20 Mm below the visible solar surface.The properties of convection at the main energy carrying (granular scales are tightly constrained by observations, in particular by the detailed shapes of photospheric spectral lines and the topology (time- and length-scales, flow velocities, etc. of the up- and downflows. Current supercomputer models match these constraints very closely, which lends credence to the models, and allows robust conclusions to be drawn from analysis of the model properties.At larger scales the properties of the convective velocity field at the solar surface are strongly influenced by constraints from mass conservation, with amplitudes of larger scale horizontal motions decreasing roughly in inverse proportion to the scale of the motion. To a large extent, the apparent presence of distinct (meso- and supergranulation scales is a result of the folding of this spectrum with the effective “filters” corresponding to various observational techniques. Convective motions on successively larger scales advect patterns created by convection on smaller scales; this includes patterns of magnetic field, which thus have an approximately self-similar structure at scales larger than granulation.Radiative-hydrodynamical simulations of solar surface convection can be used as 2D/3D time-dependent models of the solar atmosphere to predict the emergent spectrum. In general, the resulting detailed spectral line profiles agree spectacularly well with observations without invoking any micro- and macroturbulence parameters due to the presence of convective velocities and atmosphere inhomogeneities. One of the most noteworthy results has been a significant reduction in recent years in the derived solar C, N, and O abundances with

  12. Friction Surfacing In Steel 304


    S. Godwin Barnabas; Anantharam; Shyam sundar; B.S.Aravind T.Prabhu


    Surface engineering deals with the surface of the solid matter and it is sub-discipline of The surface phase of a solid interacts with the surrounding environment. This interaction can degrade the surface phase over time, may result in loss of material from its surface. Environmental degradation of the surface phase over time can be caused by wear, corrosion, creep, fatigue loads, shear loads, tensile loads, cutting forces or when exposed to higher temperature. Wear can be minimiz...

  13. Scraped surface heat exchangers. (United States)

    Rao, Chetan S; Hartel, Richard W


    Scraped surface heat exchangers (SSHEs) are commonly used in the food, chemical, and pharmaceutical industries for heat transfer, crystallization, and other continuous processes. They are ideally suited for products that are viscous, sticky, that contain particulate matter, or that need some degree of crystallization. Since these characteristics describe a vast majority of processed foods, SSHEs are especially suited for pumpable food products. During operation, the product is brought in contact with a heat transfer surface that is rapidly and continuously scraped, thereby exposing the surface to the passage of untreated product. In addition to maintaining high and uniform heat exchange, the scraper blades also provide simultaneous mixing and agitation. Heat exchange for sticky and viscous foods such as heavy salad dressings, margarine, chocolate, peanut butter, fondant, ice cream, and shortenings is possible only by using SSHEs. High heat transfer coefficients are achieved because the boundary layer is continuously replaced by fresh material. Moreover, the product is in contact with the heating surface for only a few seconds and high temperature gradients can be used without the danger of causing undesirable reactions. SSHEs are versatile in the use of heat transfer medium and the various unit operations that can be carried out simultaneously. This article critically reviews the current understanding of the operations and applications of SSHEs.

  14. Wetting of real surfaces

    CERN Document Server

    Bormashenko, Edward Yu


    The problem of wetting and drop dynamics on various surfaces is very interesting from both the scientificas well as thepractical viewpoint, and subject of intense research.The results are scattered across papers in journals, sothis workwill meet the need for a unifying, comprehensive work.

  15. Surface complexation modeling (United States)

    Adsorption-desorption reactions are important processes that affect the transport of contaminants in the environment. Surface complexation models are chemical models that can account for the effects of variable chemical conditions, such as pH, on adsorption reactions. These models define specific ...

  16. A Thermochromic Superhydrophobic Surface (United States)

    Cataldi, Pietro; Bayer, Ilker S.; Cingolani, Roberto; Marras, Sergio; Chellali, Ryad; Athanassiou, Athanassia


    Highly enhanced solid-state thermochromism is observed in regioregular poly(3-hexylthiophene), P3HT, when deposited on a superhydrophobic polymer-SiO2 nanocomposite coating. The conformal P3HT coating on the nanocomposite surface does not alter or reduce superhydrophicity while maintaining its reversible enhanced thermochromism. The polymeric matrix of the superhydrophobic surface is comprised of a blend of poly(vinylidene fluoride-co-hexafluoropropylene) copolymer and an acrylic adhesive. Based on detailed X-ray diffraction measurements, this long-lasting, repeatable and hysteresis-free thermochromic effect is attributed to the enhancement of the Bragg peak associated with the d-spacing of interchain directional packing (100) which remains unaltered during several heating-cooling cycles. We propose that the superhydrophobic surface confines π-π interchain stacking in P3HT with uniform d-spacing into its nanostructured texture resulting in better packing and reduction in face-on orientation. The rapid response of the system to sudden temperature changes is also demonstrated by water droplet impact and bounce back on heated surfaces. This effect can be exploited for embedded thin film temperature sensors for metal coatings.

  17. Real Compact Surfaces

    Indian Academy of Sciences (India)

    The classification of real compact surfaces is a main result which is at the same time easy to understand and non- trivial, simple in formulation and rich in consequences. The aim of this article is to explain the theorem by means of many drawings. It is an invitation to a visual approach of mathematics. First Definitions and ...

  18. Hydrological land surface modelling

    DEFF Research Database (Denmark)

    Ridler, Marc-Etienne Francois

    and disaster management. The objective of this study is to develop and investigate methods to reduce hydrological model uncertainty by using supplementary data sources. The data is used either for model calibration or for model updating using data assimilation. Satellite estimates of soil moisture and surface...

  19. Predictive Surface Complexation Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Sverjensky, Dimitri A. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Earth and Planetary Sciences


    Surface complexation plays an important role in the equilibria and kinetics of processes controlling the compositions of soilwaters and groundwaters, the fate of contaminants in groundwaters, and the subsurface storage of CO2 and nuclear waste. Over the last several decades, many dozens of individual experimental studies have addressed aspects of surface complexation that have contributed to an increased understanding of its role in natural systems. However, there has been no previous attempt to develop a model of surface complexation that can be used to link all the experimental studies in order to place them on a predictive basis. Overall, my research has successfully integrated the results of the work of many experimentalists published over several decades. For the first time in studies of the geochemistry of the mineral-water interface, a practical predictive capability for modeling has become available. The predictive correlations developed in my research now enable extrapolations of experimental studies to provide estimates of surface chemistry for systems not yet studied experimentally and for natural and anthropogenically perturbed systems.

  20. on Perforated Surfaces

    African Journals Online (AJOL)

    Research note. Assffisment of the Perfonnance of Sun Drying of Maize Grains on Perforated Surfaces. Silayo*, V.c.K., S.T.A.R. Kajuna and B.Omari. Sokoine University of Agriculture, P.O. Box 3003, Morogoro, Tanzania. Abstract. Sun drying of maize grains on different mesh sizes ofperjorated trays using different heights.

  1. Surface explosion cavities

    CERN Document Server

    Benusiglio, Adrien; Clanet, Christophe


    We present a fluid dynamics video on cavities created by explosions of firecrackers at the water free surface. We use three types of firecrackers containing 1, 1.3 and 5 g of flash powder. The firecrackers are held with their center at the surface of water in a cubic meter pool. The movies are recorded from the side with a high-speed video camera. Without confinement the explosion produces an hemispherical cavity. Right after the explosion this cavity grows isotropically, the bottom then stops while the sides continue to expand. In the next phase the bottom of the cavity accelerates backwards to the surface. During this phase the convergence of the flow creates a central jet that rises above the free surface. In the last part of the video the explosion is confined in a vertical open tube made of glass and of centimetric diameter. The explosion creates a cylindrical cavity that develops towards the free end of the tube. Depending on the charge, the cavity can either stop inside the tube or at its exit, but nev...

  2. Paneling architectural freeform surfaces

    KAUST Repository

    Eigensatz, Michael


    The emergence of large-scale freeform shapes in architecture poses big challenges to the fabrication of such structures. A key problem is the approximation of the design surface by a union of patches, socalled panels, that can be manufactured with a selected technology at reasonable cost, while meeting the design intent and achieving the desired aesthetic quality of panel layout and surface smoothness. The production of curved panels is mostly based on molds. Since the cost of mold fabrication often dominates the panel cost, there is strong incentive to use the same mold for multiple panels. We cast the major practical requirements for architectural surface paneling, including mold reuse, into a global optimization framework that interleaves discrete and continuous optimization steps to minimize production cost while meeting user-specified quality constraints. The search space for optimization is mainly generated through controlled deviation from the design surface and tolerances on positional and normal continuity between neighboring panels. A novel 6-dimensional metric space allows us to quickly compute approximate inter-panel distances, which dramatically improves the performance of the optimization and enables the handling of complex arrangements with thousands of panels. The practical relevance of our system is demonstrated by paneling solutions for real, cutting-edge architectural freeform design projects. © 2010 ACM.

  3. Paneling architectural freeform surfaces

    KAUST Repository

    Eigensatz, Michael


    The emergence of large-scale freeform shapes in architecture poses big challenges to the fabrication of such structures. A key problem is the approximation of the design surface by a union of patches, so-called panels, that can be manufactured with a selected technology at reasonable cost, while meeting the design intent and achieving the desired aesthetic quality of panel layout and surface smoothness. The production of curved panels is mostly based on molds. Since the cost of mold fabrication often dominates the panel cost, there is strong incentive to use the same mold for multiple panels. We cast the major practical requirements for architectural surface paneling, including mold reuse, into a global optimization framework that interleaves discrete and continuous optimization steps to minimize production cost while meeting user-specified quality constraints. The search space for optimization is mainly generated through controlled deviation from the design surface and tolerances on positional and normal continuity between neighboring panels. A novel 6-dimensional metric space allows us to quickly compute approximate inter-panel distances, which dramatically improves the performance of the optimization and enables the handling of complex arrangements with thousands of panels. The practical relevance of our system is demonstrated by paneling solutions for real, cutting-edge architectural freeform design projects.

  4. Biofunctional surface engineering

    CERN Document Server

    Scholz, Martin


    PrefaceRegulatory issuesSterilization of combination devicesPolyelectrolyte monolayers (I)Polyelectrolyte monolayers (II)Surface modificationsThree dimensional characterization of immobilized biomolecules Aptamers for biofunctionalization of stentsCoating of implants with antibioticsMicroneedles and nanopatchesfor vaccinationMicrochips for antibody binding analysesBiofunctionalized wound dressingsExtracorporeal device for trapping circulating tumor cellsOutlook

  5. Unbonded Aggregate Surface Roads (United States)


    riding surface (DA 1990).” The grada - tions in Table 1 become finer as one proceeds from grading No. 1 to grading No. 4. Figures 1 through 4 compare...a good opportunity for quantifying changes in grada - tion under traffic. A study for this purpose, as well as for quantifying the plastic- ity of


    African Journals Online (AJOL)

    1: Tilting table apparatus for the determination of friction coefficient. The friction surface with the cylinder resting on was gradually lifted (inclined) with the bolt and nut-arrangement until the cylinder, along with the sample just began to slide down. At this point, the bolt adjustment was stopped and the. ' angle which was made ...

  7. Surface Water in Hawaii (United States)

    Oki, Delwyn S.


    Surface water in Hawaii is a valued resource as well as a potential threat to human lives and property. The surface-water resources of Hawaii are of significant economic, ecologic, cultural, and aesthetic importance. Streams supply more than 50 percent of the irrigation water in Hawaii, and although streams supply only a few percent of the drinking water statewide, surface water is the main source of drinking water in some places. Streams also are a source of hydroelectric power, provide important riparian and instream habitats for many unique native species, support traditional and customary Hawaiian gathering rights and the practice of taro cultivation, and possess valued aesthetic qualities. Streams affect the physical, chemical, and aesthetic quality of receiving waters, such as estuaries, bays, and nearshore waters, which are critical to the tourism-based economy of the islands. Streams in Hawaii pose a danger because of their flashy nature; a stream's stage, or water level, can rise several feet in less than an hour during periods of intense rainfall. Streams in Hawaii are flashy because rainfall is intense, drainage basins are small, basins and streams are steep, and channel storage is limited. Streamflow generated during periods of heavy rainfall has led to loss of property and human lives in Hawaii. Most Hawaiian streams originate in the mountainous interiors of the islands and terminate at the coast. Streams are significant sculptors of the Hawaiian landscape because of the erosive power of the water they convey. In geologically young areas, such as much of the southern part of the island of Hawaii, well-defined stream channels have not developed because the permeability of the surface rocks generally is so high that rainfall infiltrates before flowing for significant distances on the surface. In geologically older areas that have received significant rainfall, streams and mass wasting have carved out large valleys.


    Directory of Open Access Journals (Sweden)

    DĂNĂILĂ Ligia


    Full Text Available The paper work proposes practical graphic methods provided by Descriptive Geometry to plot the development of two revolution surfaces: the revolution surface having an oval as median section and the revolution surface having an ordinary curve as median section. The two surfaces were selected because their developments have similarities when plotted.

  9. Surface decontamination compositions and methods (United States)

    Wright,; Karen, E [Idaho Falls, ID; Cooper, David C [Idaho Falls, ID; Peterman, Dean R [Idaho Falls, ID; Demmer, Ricky L [Idaho Falls, ID; Tripp, Julia L [Pocatello, ID; Hull, Laurence C [Idaho Falls, ID


    Clay-based compositions capable of absorbing contaminants from surfaces or objects having surface faces may be applied to a surface and later removed, the removed clay-based compositions absorbing at least a portion of the contaminant from the surface or object to which it was applied.

  10. Surface Plasmon Nanophotonics

    CERN Document Server

    Brongersma, Mark L


    The development of advanced dielectric photonic structures has enabled tremendous control over the propagation and manipulation of light. Structures such as waveguides, splitters, mixers, and resonators now play a central role in the telecommunications industry. This book will discuss an exciting new class of photonic devices, known as surface plasmon nanophotonic structures. Surface plasmons are easily accessible excitations in metals and semiconductors and involve a collective motion of the conduction electrons. These excitations can be exploited to manipulate electromagnetic waves at optical frequencies ("light") in new ways that are unthinkable in conventional dielectric structures. The field of plasmon nanophotonics is rapidly developing and impacting a wide range of areas including: electronics, photonics, chemistry, biology, and medicine. The book will highlight several exciting new discoveries that have been made, while providing a clear discussion of the underlying physics, the nanofabrication issues...

  11. Parsimonious Surface Wave Interferometry

    KAUST Repository

    Li, Jing


    To decrease the recording time of a 2D seismic survey from a few days to one hour or less, we present a parsimonious surface-wave interferometry method. Interferometry allows for the creation of a large number of virtual shot gathers from just two reciprocal shot gathers by crosscoherence of trace pairs, where the virtual surface waves can be inverted for the S-wave velocity model by wave-equation dispersion inversion (WD). Synthetic and field data tests suggest that parsimonious wave-equation dispersion inversion (PWD) gives S-velocity tomograms that are comparable to those obtained from a full survey with a shot at each receiver. The limitation of PWD is that the virtual data lose some information so that the resolution of the S-velocity tomogram can be modestly lower than that of the S-velocity tomogram inverted from a conventional survey.

  12. Surface Plasmon Singularities

    Directory of Open Access Journals (Sweden)

    Gabriel Martínez-Niconoff


    Full Text Available With the purpose to compare the physical features of the electromagnetic field, we describe the synthesis of optical singularities propagating in the free space and on a metal surface. In both cases the electromagnetic field has a slit-shaped curve as a boundary condition, and the singularities correspond to a shock wave that is a consequence of the curvature of the slit curve. As prototypes, we generate singularities that correspond to fold and cusped regions. We show that singularities in free space may generate bifurcation effects while plasmon fields do not generate these kinds of effects. Experimental results for free-space propagation are presented and for surface plasmon fields, computer simulations are shown.

  13. Focal surfaces of hyperbolic cylinders (United States)

    Georgiev, Georgi Hristov; Pavlov, Milen Dimov


    Cylindrical surfaces have many applications in geometric modeling, architecture and other branches of engineering. In this paper, we describe two cylindrical surfaces associated to a given hyperbolic cylinder. The first one is a focal surface which is determined by reciprocal principle curvature of the hyperbolic cylinder. The second one is a generalized focal surface obtained by reciprocal mean curvature of the same hyperbolic cylinder. In particular, we show that each of these surfaces admits three different parametric representations. As consequence, it is proved that the focal and generalized focal surfaces of the hyperbolic cylinder are rational surfaces. An illustrative example is included.

  14. Music Mixing Surface


    Gelineck, Steven; Büchert, Morten; Andersen, Jesper


    This paper presents a multi-touch based interface for mixing music. The goal of the interface is to provide users with a more intuitive control of the music mix by implementing the so-called stage metaphor control scheme, which is especially suitable for multi-touch surfaces. Specifically, we discuss functionality important for the professional music technician (main target user) - functionality, which is especially challenging to integrate when implementing the stage metaphor. Finally we pro...

  15. Measurement of Surface Forces (United States)


    structural force is often observed on hydrophilic and hydrophobic surfaces, respectively. These forces are referred to in the literature as hydration and...47,481. One parameter, the effective molecular diffusivity in a pore (e.g., zeolite or polymer), has been indirectly related to transport limited rates...adhesion force (2 g.N) and a marked increase in rate of Fe(CN)6 -3 reduction. Both effects were ascribed to the more hydrophilic nature of the activated

  16. Surface Sampling Techniques (United States)


    their suitability for use for qualitative analysis of explosiveu/ explosivo residues oil the surface types of interest. Tables 11-5 and 11-6 list spot teot...below: Analytes Tested NG Nitroglycerin PETN Pentaerythritetetranitrate RDX Cyclotrimethylenetrinitramine TNT 2,4,6-trinitrotoluene TNB 1,3,5...acetonitrile had evaporated, the paper was examined under 254 nm UV illumination. All of the analytes except NG and PETN were detecr.ed at the 10OX

  17. Music Mixing Surface

    DEFF Research Database (Denmark)

    Gelineck, Steven; Büchert, Morten; Andersen, Jesper


    This paper presents a multi-touch based interface for mixing music. The goal of the interface is to provide users with a more intuitive control of the music mix by implementing the so-called stage metaphor control scheme, which is especially suitable for multi-touch surfaces. Specifically, we...... discuss functionality important for the professional music technician (main target user) - functionality, which is especially challenging to integrate when implementing the stage metaphor. Finally we propose and evaluate solutions to these challenges....

  18. Amphoteric surface active agents

    Directory of Open Access Journals (Sweden)

    Eissa, A.M. F.


    Full Text Available 2-[trimethyl ammonium, triethyl ammonium, pyridinium and 2-amino pyridinium] alkanoates, four series of surface active agents containing carbon chain C12, C14, C16 and C18carbon atoms, were prepared. Their structures were characterized by microanalysis, infrared (IR and nuclear magnetic resonance (NMR. Surface and interfacial tension, Krafft point, wetting time, emulsification power, foaming height and critical micelle concentration (cmc were determined and a comparative study was made between their chemical structure and surface active properties. Antimicrobial activity of these surfactants was also determined.

    Se prepararon cuatro series de agentes tensioactivos del tipo 2-[trimetil amonio, trietil amonio, piridinio y 2-amino piridinio] alcanoatos, que contienen cadenas carbonadas con C12, C14, C16 y C18 átomos de carbono.
    Se determinaron la tensión superficial e interfacial, el punto de Krafft, el tiempo humectante, el poder de emulsionamiento, la altura espumante y la concentración critica de miscela (cmc y se hizo un estudio comparativo entre la estructura química y sus propiedades tensioactivas. Se determinó también la actividad antimicrobiana de estos tensioactivos. Estas estructuras se caracterizaron por microanálisis, infrarrojo (IR y resonancia magnética nuclear (RMN.

  19. High surface area calcite (United States)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.


    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  20. Hemocompatibility of Polymeric Nanostructured Surfaces (United States)

    Leszczak, Victoria; Smith, Barbara S.; Popat, Ketul C.


    Tissue integration is an important property when inducing transplant tolerance, however, the hemocompatibility of the biomaterial surface also plays an important role in the ultimate success of the implant. Therefore, in order to induce transplant tolerance, it is critical to understand the interaction of blood components with the material surfaces. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets and clotting kinetics of whole blood on flat polycaprolactone (PCL) surfaces, nanowire (NW) surfaces and nanofiber (NF) surfaces. Previous studies have shown that polymeric nanostructured surfaces improve cell adhesion, proliferation and viability; however it is unclear how these polymeric nanostructured surfaces interact with the blood and its components. Protein adsorption results indicate that while there were no significant differences in total albumin adsorption on PCL, NW and NF surfaces, NW surfaces had higher total fibrinogen and immunoglobulin-G adsorption compared to NF and PCL surfaces. In contrast, NF surfaces had higher surface FIB and IgG adsorption compared to PCL and NW surfaces. Platelet adhesion and viability studies show more adhesion and clustering of platelets on the NF surfaces as compared to PCL and NW surfaces. Platelet activation studies reveal that NW surfaces have the highest percentage of unactivated platelets, whereas NF surfaces have the highest percentage of fully activated platelets. Whole blood clotting results indicate that NW surfaces maintain an increased amount of free hemoglobin during the clotting process compared to PCL and NF surface, indicating less clotting and slower rate of clotting on their surfaces. PMID:23848447

  1. Lateral engineering of surface states - towards surface-state nanoelectronics. (United States)

    García de Abajo, F J; Cordón, J; Corso, M; Schiller, F; Ortega, J E


    Patterned metal surfaces can host electron quantum waves that display interference phenomena over distances of a few nanometres, thus providing excellent information carriers for future atomic-scale devices. Here we demonstrate that collimation and waveguiding of surface electrons can be realized in silver-induced strain dislocation networks on Cu(111) surfaces, as a conceptual proof-of-principle of surface-state nanoelectronics (SSNE). The Ag/Cu(111) system exhibits featured surface bands with gaps at the Fermi energy, which are basic requirements for a potential SSNE material. We establish a solid analogy between the behavior of surface-state electrons and surface plasmons in patterned metal surfaces, thus facilitating the transfer of existing knowledge on plasmonic structures to the new scenario presented by engineered electronic surface-state nanostructures, with the advantage of a 1000-fold reduction in wavelength and geometrical parameters.

  2. Surface nanobubbles and micropancakes (United States)

    Seddon, James R. T.


    When looking at a wetted surface with a technique that can probe the nanoscale, a high surface coverage of gas bubbles is often revealed. So what? Well, if we believe in classical diffusion, these bubbles should dissolve in microseconds, but in reality they are found to remain stable for as long as anyone has observed (five days thus far, which is 10-11 orders of magnitude longer than would be expected). As well as the obvious question of why the lifetime is so long, and also the question of how the bubbles nucleate in the first place, we rapidly find ourselves asking can we use the bubbles to our benefit? A clear example would be in controlling slip in micro/nanofluidics: effectively, replacing a solid wall with a 'gassy' wall replaces the no-slip boundary condition with one of slip. Several other potential applications have also been suggested and nanobubbles have, in fact, already proven useful in the antifouling world. Returning to fundamentals, another near-wall gas domain has also come to light through our investigations into nanobubbles. The micropancake is thought to be a quasi-2D dense adsorbate of gas molecules (i.e. N2 or O2) which grows epitaxially on the surface. New questions now include: why are micropancakes stable, how do they form, and what is their relationship with nanobubbles? Progress is being made in this field and, as with all new topics, the community is rapidly converging toward a standard set of 'minimum' requirements for scientific reporting. For example, taking single-shot atomic force microscopy data is almost definitely no longer sufficient to be additive to the field (there are far too many unrepeatable single-shot measurements in the literature which are too often used as 'evidence', even though there are a seemingly equal number of single-shot measurements that may disagree). Just quoting a 'set-point' is now also insufficient (both set-point and free (or interaction) amplitude are required to know the applied force of an AFM

  3. Conversion from surface wave to surface wave on reflection

    DEFF Research Database (Denmark)

    Novitsky, Andrey


    We discuss the reflection and transmission of an incident surface wave to a pure surface wave state at another interface. This is allowed only for special media parameters: at least one of the media must be magnetic. We found such material characteristics that the obliquely incident surface wave...... can be transmitted without changing its direction (nevertheless the amplitude varies). For other media parameters, only normally incident surface waves can be converted to surface waves. We propose applications of the predicted conversion as a beam splitter and polarization filter for surface waves....

  4. Imaging of surfaces by concurrent surface plasmon resonance and surface plasmon resonance-enhanced fluorescence.

    Directory of Open Access Journals (Sweden)

    Rahber Thariani

    Full Text Available Surface plasmon resonance imaging and surface plasmon induced fluorescent are sensitive tools for surface analysis. However, existing instruments in this area have provided limited capability for concurrent detection, and may be large and expensive. We demonstrate a highly cost-effective system capable of concurrent surface plasmon resonance microscopy (SPRM and surface plasmon resonance-enhanced fluorescence (SPRF imaging, allowing for simultaneous monitoring of reflectivity and fluorescence from discrete spatial regions. The instrument allows for high performance imaging and quantitative measurements with surface plasmon resonance, and surface plasmon induced fluorescence, with inexpensive off-the-shelf components.

  5. Nature Inspired Surface Coatings (United States)

    Rubner, Michael


    Materials Scientists more and more are looking to nature for clues on how to create highly functional surface coatings with exceptional properties. The fog harvesting capabilities of the Namib Desert beetle, the beautiful iridescent colors of the hummingbird, and the super water repellant abilities of the Lotus leaf are but a few examples of the amazing properties developed over many years in the natural world. Nature also makes extensive use of the pH-dependent behavior of weak functional groups such as carboxylic acid and amine functional groups. This presentation will explore synthetic mimics to the nano- and microstructures responsible for these fascinating properties. For example, we have demonstrated a pH-induced porosity transition that can be used to create porous films with pore sizes that are tunable from the nanometer scale to the multiple micron scale. The pores of these films, either nano- or micropores, can be reversibly opened and closed by changes in solution pH. The ability to engineer pH-gated porosity transitions in heterostructured thin films has led to the demonstration of broadband anti-reflection coatings that mimic the anti-reflection properties of the moth eye and pH-tunable Bragg reflectors with a structure and function similar to that found in hummingbird wings and the Longhorn beetle. In addition, the highly textured honeycomb-like surfaces created by the formation of micron-scale pores are ideally suited for the creation of superhydrophobic surfaces that mimic the behavior of the self-cleaning lotus leaf. The development of synthetic "backbacks" on immune system cells that may one day ferry drugs to disease sites will also be discussed.

  6. Surface modified aerogel monoliths (United States)

    Leventis, Nicholas (Inventor); Johnston, James C. (Inventor); Kuczmarski, Maria A. (Inventor); Meador, Mary Ann B. (Inventor)


    This invention comprises reinforced aerogel monoliths such as silica aerogels having a polymer coating on its outer geometric surface boundary, and to the method of preparing said aerogel monoliths. The polymer coatings on the aerogel monoliths are derived from polymer precursors selected from the group consisting of isocyanates as a precursor, precursors of epoxies, and precursors of polyimides. The coated aerogel monoliths can be modified further by encapsulating the aerogel with the polymer precursor reinforced with fibers such as carbon or glass fibers to obtain mechanically reinforced composite encapsulated aerogel monoliths.

  7. Distributed Surface Force (United States)


    ships built in the United States, and designs that could be available from the international market . The small SSC can be easily broken into two...capability. The team markets the distributed surface concept as the armada, or a combination of SSC ships and other U.S. Navy assets, to further reinforce...32526 34 615000 279 0.01938 Cape Verde P511 5800 23 639160 290 0.01088 S. Korea Sea Wolf 14640 25 694260 315 0.02024 Angola Rei Ekuiki II 4732 20

  8. Modeling surface imperfections in thin films and nanostructured surfaces

    DEFF Research Database (Denmark)

    Hansen, Poul-Erik; Madsen, J. S.; Jensen, S. A.


    Accurate scatterometry and ellipsometry characterization of non-perfect thin films and nanostructured surfaces are challenging. Imperfections like surface roughness make the associated modelling and inverse problem solution difficult due to the lack of knowledge about the imperfection...

  9. Minimalist surface-colour matching. (United States)

    Amano, Kinjiro; Foster, David H; Nascimento, Sérgio M C


    Some theories of surface-colour perception assume that observers estimate the illuminant on a scene so that its effects can be discounted. A critical test of this interpretation of colour constancy is whether surface-colour matching is worse when the number of surfaces in a scene is so small that any illuminant estimate is unreliable. In the experiment reported here, observers made asymmetric colour matches between pairs of simultaneously presented Mondrian-like patterns under different daylights. The patterns had either 49 surfaces or a minimal 2 surfaces. No significant effect of number was found, suggesting that illuminant estimates are unnecessary for surface-colour matching.

  10. Surface Chemistry in Nanoscale Materials

    Directory of Open Access Journals (Sweden)

    Alex V. Hamza


    Full Text Available Although surfaces or, more precisely, the surface atomic and electronic structure, determine the way materials interact with their environment, the influence of surface chemistry on the bulk of the material is generally considered to be small. However, in the case of high surface area materials such as nanoporous solids, surface properties can start to dominate the overall material behavior. This allows one to create new materials with physical and chemical properties that are no longer determined by the bulk material, but by their nanoscale architectures. Here, we discuss several examples, ranging from nanoporous gold to surface engineered carbon aerogels that demonstrate the tuneability of nanoporous solids for sustainable energy applications.

  11. Surface Chemistry in Nanoscale Materials (United States)

    Biener, Jürgen; Wittstock, Arne; Baumann, Theodore F.; Weissmüller, Jörg; Bäumer, Marcus; Hamza, Alex V.


    Although surfaces or, more precisely, the surface atomic and electronic structure, determine the way materials interact with their environment, the influence of surface chemistry on the bulk of the material is generally considered to be small. However, in the case of high surface area materials such as nanoporous solids, surface properties can start to dominate the overall material behavior. This allows one to create new materials with physical and chemical properties that are no longer determined by the bulk material, but by their nanoscale architectures. Here, we discuss several examples, ranging from nanoporous gold to surface engineered carbon aerogels that demonstrate the tuneability of nanoporous solids for sustainable energy applications.

  12. Surface tension of spherical drops from surface of tension

    Energy Technology Data Exchange (ETDEWEB)

    Homman, A.-A.; Bourasseau, E. [CEA/DAM DIF, F-91297 Arpajon Cedex (France); Stoltz, G. [Université Paris-Est, CERMICS (ENPC), INRIA, F-77455 Marne-la-Vallée (France); Malfreyt, P. [Institut de Chimie de Clermont-Ferrand, Université Blaise Pascal, UMR CNRS 6296, ICCF, BP 10448, F-63000 Clermont-Ferrand (France); Strafella, L.; Ghoufi, A., E-mail: [Institut de Physique de Rennes, Université de Rennes 1 UMR 6251 CNRS, 263 avenue Général Leclerc, 35042 Rennes (France)


    The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

  13. Test surfaces useful for calibration of surface profilometers (United States)

    Yashchuk, Valeriy V; McKinney, Wayne R; Takacs, Peter Z


    The present invention provides for test surfaces and methods for calibration of surface profilometers, including interferometric and atomic force microscopes. Calibration is performed using a specially designed test surface, or the Binary Pseudo-random (BPR) grating (array). Utilizing the BPR grating (array) to measure the power spectral density (PSD) spectrum, the profilometer is calibrated by determining the instrumental modulation transfer.

  14. Upscaling and downscaling of land surface fluxes with surface temperature (United States)

    Land surface temperature (LST) is a key surface boundary condition that is significantly correlated to surface flux partitioning between latent and sensible heat. The spatial and temporal variation in LST is driven by radiation, wind, vegetation cover and roughness as well as soil moisture status ...

  15. Smooth surfaces from bilinear patches: Discrete affine minimal surfaces

    KAUST Repository

    Käferböck, Florian


    Motivated by applications in freeform architecture, we study surfaces which are composed of smoothly joined bilinear patches. These surfaces turn out to be discrete versions of negatively curved affine minimal surfaces and share many properties with their classical smooth counterparts. We present computational design approaches and study special cases which should be interesting for the architectural application. 2013 Elsevier B.V.

  16. Femtosecond laser-induced surface wettability modification of polystyrene surface (United States)

    Wang, Bing; Wang, XinCai; Zheng, HongYu; Lam, YeeCheong


    In this paper, we demonstrated a simple method to create either a hydrophilic or hydrophobic surface. With femtosecond laser irradiation at different laser parameters, the water contact angle (WCA) on polystyrene's surface can be modified to either 12.7° or 156.2° from its original WCA of 88.2°. With properly spaced micro-pits created, the surface became hydrophilic probably due to the spread of the water droplets into the micro-pits. While with properly spaced micro-grooves created, the surface became rough and more hydrophobic. We investigated the effect of laser parameters on WCAs and analyzed the laser-treated surface roughness, profiles and chemical bonds by surface profilometer, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). For the laser-treated surface with low roughness, the polar (such as C—O, C=O, and O—C=O bonds) and non-polar (such as C—C or C—H bonds) groups were found to be responsible for the wettability changes. While for a rough surface, the surface roughness or the surface topography structure played a more significant role in the changes of the surface WCA. The mechanisms involved in the laser surface wettability modification process were discussed.

  17. Relationship of wood surface energy to surface composition (United States)

    Feipeng P. Liu; Timothy G. Rials; John Simonsen


    The wood cell wall is composed of cellulose, lignin, hemicelluloses, and extractives. Thus, the surface energy of the wood material must be some combination of the surface energies of these components. The influence of extractives on wood surface chemistry can be important in diverse industrial applications, such as coating, pulping, and wood-based composites. In this...

  18. Surface energy and surface tension of liquid metal nanodrops

    Directory of Open Access Journals (Sweden)

    Shebzukhov A.A.


    Full Text Available A unitary approach has been proposed for the calculation of surface energy and surface tension of nanoparticle being in equilibrium with its saturated vapor on both flat and curved surfaces at given temperature. The final equations involve parameters dependent on the type of premelting structure: bcc, fcc or hcp.

  19. Surface plasmon enhanced FRET (United States)

    Steele, Jennifer M.; Ramnarace, Chae M.; Farner, William R.


    We demonstrate an increase in Förster Resonance Energy Transfer (FRET) efficiency for paired fluorescent molecules on gold nanogratings for a range of acceptor concentrations. For gratings, the periodicity allows for a broad range of surface plasmon wavelengths that follow a dispersion relationship. The dispersion relationship is determined by the periodicity of the grating and the dielectric function of the metal that makes the grating. Locating a fluorophore near a plasmonic metal structure increases the emission in two ways - an excitation enhancement and an emission modification. The second mechanism occurs when the plasmonic substrate increases the local density of optical states (LDOS). This has the effect of shortening the lifetime of the excited state which increases the quantum yield of the fluorophore. In this work, gold wire nanogratings with a period of 500 nm were fabricated. We used Atto 532 and Atto 633 as the donor and acceptor FRET molecules respectively. A thin layer of PVA containing different concentrations of the donor and acceptor FRET molecules was spun cast onto the gratings. The donor molecules were excited with a 532 nm laser, and the fluorescence emission from both the donor and acceptor molecules were recorded. We found that for all concentrations of acceptors, the FRET efficiency was the largest when the surface plasmon modes overlapped the acceptor emission. Compared to the unenhanced efficiency, the largest gains in efficiency were measured for the lowest concentration of acceptors.


    Energy Technology Data Exchange (ETDEWEB)

    Mansur, Louis K [ORNL; Bhattacharya, R [UES, Incorporated, Dayton, OH; Blau, Peter Julian [ORNL; Clemons, Art [ORNL; Eberle, Cliff [ORNL; Evans, H B [UES, Incorporated, Dayton, OH; Janke, Christopher James [ORNL; Jolly, Brian C [ORNL; Lee, E H [Consultant, Milpitas, CA; Leonard, Keith J [ORNL; Trejo, Rosa M [ORNL; Rivard, John D [ORNL


    High energy ion beam surface treatments were applied to a selected group of polymers. Of the six materials in the present study, four were thermoplastics (polycarbonate, polyethylene, polyethylene terephthalate, and polystyrene) and two were thermosets (epoxy and polyimide). The particular epoxy evaluated in this work is one of the resins used in formulating fiber reinforced composites for military helicopter blades. Measures of mechanical properties of the near surface regions were obtained by nanoindentation hardness and pin on disk wear. Attempts were also made to measure erosion resistance by particle impact. All materials were hardness tested. Pristine materials were very soft, having values in the range of approximately 0.1 to 0.5 GPa. Ion beam treatment increased hardness by up to 50 times compared to untreated materials. For reference, all materials were hardened to values higher than those typical of stainless steels. Wear tests were carried out on three of the materials, PET, PI and epoxy. On the ion beam treated epoxy no wear could be detected, whereas the untreated material showed significant wear.

  1. Earth's surface heat flux

    Directory of Open Access Journals (Sweden)

    J. H. Davies


    Full Text Available We present a revised estimate of Earth's surface heat flux that is based upon a heat flow data-set with 38 347 measurements, which is 55% more than used in previous estimates. Our methodology, like others, accounts for hydrothermal circulation in young oceanic crust by utilising a half-space cooling approximation. For the rest of Earth's surface, we estimate the average heat flow for different geologic domains as defined by global digital geology maps; and then produce the global estimate by multiplying it by the total global area of that geologic domain. The averaging is done on a polygon set which results from an intersection of a 1 degree equal area grid with the original geology polygons; this minimises the adverse influence of clustering. These operations and estimates are derived accurately using methodologies from Geographical Information Science. We consider the virtually un-sampled Antarctica separately and also make a small correction for hot-spots in young oceanic lithosphere. A range of analyses is presented. These, combined with statistical estimates of the error, provide a measure of robustness. Our final preferred estimate is 47±2 TW, which is greater than previous estimates.

  2. Concepts in surface physics

    CERN Document Server

    Desjonquères, M -C


    This textbook is intended as an introduction to surface science for graduate students. It began as a course of lectures that we gave at the University of Paris (Orsay). Its main objectives are twofold: to provide the reader with a compre­ hensive presentation of the basic principles and concepts of surface physics and to show the usefulness of these concepts in the real world by referring to experiments. It starts at a rather elementary level since it only requires a knowledge of solid state physics, quantum mechanics, thermodynamics and statistical physics which does not exceed the background usually taught to students early in their university courses. However, since it finally reaches an advanced level, we have tried to render it as self-contained as possible so that it remains accessible even to an unexperienced reader. Furthermore, the emphasis has been put on a pedagogical level rather than on a technical level. In this spirit, whenever possible, models which are simplified, but which contain the featu...

  3. Pose Space Surface Manipulation

    Directory of Open Access Journals (Sweden)

    Yusuke Yoshiyasu


    Full Text Available Example-based mesh deformation techniques produce natural and realistic shapes by learning the space of deformations from examples. However, skeleton-based methods cannot manipulate a global mesh structure naturally, whereas the mesh-based approaches based on a translational control do not allow the user to edit a local mesh structure intuitively. This paper presents an example-driven mesh editing framework that achieves both global and local pose manipulations. The proposed system is built with a surface deformation method based on a two-step linear optimization technique and achieves direct manipulations of a model surface using translational and rotational controls. With the translational control, the user can create a model in natural poses easily. The rotational control can adjust the local pose intuitively by bending and twisting. We encode example deformations with a rotation-invariant mesh representation which handles large rotations in examples. To incorporate example deformations, we infer a pose from the handle translations/rotations and perform pose space interpolation, thereby avoiding involved nonlinear optimization. With the two-step linear approach combined with the proposed multiresolution deformation method, we can edit models at interactive rates without losing important deformation effects such as muscle bulging.

  4. Waveguiding with surface plasmon polaritons

    DEFF Research Database (Denmark)

    Han, Zhanghua; Bozhevolnyi, Sergey I.


    Surface plasmon polaritons (SPPs) are electromagnetic modes propagating along metal-dielectric interfaces. Various SPP modes can be supported by flat and curved, single and multiple surfaces, exhibiting remarkable properties, including the possibility of concentrating electromagnetic fields beyond...

  5. Thermochemical surface engineering of steels

    DEFF Research Database (Denmark)

    Thermochemical Surface Engineering of Steels provides a comprehensive scientific overview of the principles and different techniques involved in thermochemical surface engineering, including thermodynamics, kinetics principles, process technologies and techniques for enhanced performance of steels...

  6. Phosphate Surface Treatments on Steel. (United States)


  7. Solvay Conference on Surface Science

    CERN Document Server


    The articles collected in this volume give a broad overview of the current state of surface science. Pioneers in the field and researchers met together at this Solvay Conference to discuss important new developments in surface science, with an emphasis on the common area between solid state physics and physical chemistry. The contributions deal with the following subjects: structure of surfaces, surface science and catalysis, two-dimensional physics and phase transitions, scanning tunneling microscopy, surface scattering and surface dynamics, chemical reactions at surfaces, solid-solid interfaces and superlattices, and surface studies with synchrotron radiation. On each of these subjects an introductory review talk and a number of short research contributions are followed by extensive discussions, which appear in full in the text. This nineteenth Solvay Conference commemorates the 75th anniversary of the Solvay Institutes.

  8. GEWEX Surface Radiation Budget (SRB) (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NASA/GEWEX Surface Radiation Budget (SRB) Release-3.0 data sets contains global 3-hourly, daily, monthly/3-hourly, and monthly averages of surface and top-of...

  9. Phase diagrams for surface alloys

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Stoltze, Per


    of the heat of segregation from the bulk and the sign of the excess interactions between the atoms in the surface (the surface mixing energy). We also consider the more complicated cases a with ordered surface phases, nonpseudomorphic overlayers, second layer segregation, and multilayers. The discussion......We discuss surface alloy phases and their stability based on surface phase diagrams constructed from the surface energy as a function of the surface composition. We show that in the simplest cases of pseudomorphic overlayers there are four generic classes of systems, characterized by the sign...... is based on density-functional calculations using the coherent-potential approximation and on effective-medium theory. We give self-consistent density-functional results for the segregation energy and surface mixing energy for all combinations of the transition and noble metals. Finally we discuss...

  10. Preperation for a Clean Surface

    Directory of Open Access Journals (Sweden)

    Aurimas Ralys


    Full Text Available The article reviews techniques for preparing clean surfaces used in the manufacturing process, considers the types of clean surfaces and their role in modern production and provides the classification methods of arranging such surfaces. The paper also discusses the principles of methods for solvent cleaning, aqueous cleaning, ultrasonic cleaning, precision cleaning and mechanical cleaning. The study focuses on the possibility of adjusting a clean surface using a water flow, including cavitation.Article in Lithuanian

  11. Flow over riblet curved surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, J B R; Freire, A P Silva, E-mail: [Mechanical Engineering Program, Federal University of Rio de Janeiro (COPPE/UFRJ), C.P. 68503, 21.941-972, Rio de Janeiro, RJ (Brazil)


    The present work studies the mechanics of turbulent drag reduction over curved surfaces by riblets. The effects of surface modification on flow separation over steep and smooth curved surfaces are investigated. Four types of two-dimensional surfaces are studied based on the morphometric parameters that describe the body of a blue whale. Local measurements of mean velocity and turbulence profiles are obtained through laser Doppler anemometry (LDA) and particle image velocimetry (PIV).

  12. Surface Waves on Metamaterials Interfaces

    DEFF Research Database (Denmark)

    Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee


    We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich...... platform for applications of surface photonics. Most of these surface waves are directional and as such their propagation can be effectively controlled by changing wavelength or material parameters tuning....

  13. Dropwise condensation of low surface tension fluids on omniphobic surfaces. (United States)

    Rykaczewski, Konrad; Paxson, Adam T; Staymates, Matthew; Walker, Marlon L; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H; Chinn, Jeff; Scott, John Henry J; Varanasi, Kripa K


    Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

  14. Dropwise Condensation of Low Surface Tension Fluids on Omniphobic Surfaces (United States)

    Rykaczewski, Konrad; Paxson, Adam T.; Staymates, Matthew; Walker, Marlon L.; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H.; Chinn, Jeff; Scott, John Henry J.; Varanasi, Kripa K.


    Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient. PMID:24595171

  15. Surface energy, elasticity and the homogenization of rough surfaces (United States)

    Mohammadi, P.; Liu, L. P.; Sharma, P.; Kukta, R. V.


    The concept of surface energy is widely used to understand numerous aspects of material behavior: fracture, self-assembly, catalysis, void formation, microstructure evolution, and size-effect exhibited by nanostructures. Extensive work exists on deriving homogenized constitutive responses for macroscopic composites—relating effective properties to various microstructural details. In the present work, we focus on homogenization of surfaces. Indeed, elucidation of the effect of surface roughness on the surface energy, stress, and elastic behavior is relatively under-studied and quite relevant to the behavior of both nanostructures and bulk material where surfaces are involved in some form or fashion. We present derivations that relate both periodic and random roughness to the effective surface elastic behavior. We find that the residual surface stress is hardly affected by roughness while the superficial elastic properties are dramatically altered and, importantly, they may also change sign—this has significant ramifications in the interpretation of sensing based on frequency measurement changes. Interestingly, even if the bare surface has a zero surface elasticity modulus, roughness is seen to endow it with one. Using atomistic calculations, we verify the qualitative validity of the obtained theoretical insights. We show, through an illustrative example, that the square of resonance frequency of a cantilever beam with rough surface can decrease almost by a factor of two compared to a flat surface.

  16. Brain Surface Conformal Parameterization Using Riemann Surface Structure (United States)

    Wang, Yalin; Lui, Lok Ming; Gu, Xianfeng; Hayashi, Kiralee M.; Chan, Tony F.; Toga, Arthur W.; Thompson, Paul M.; Yau, Shing-Tung


    In medical imaging, parameterized 3-D surface models are useful for anatomical modeling and visualization, statistical comparisons of anatomy, and surface-based registration and signal processing. Here we introduce a parameterization method based on Riemann surface structure, which uses a special curvilinear net structure (conformal net) to partition the surface into a set of patches that can each be conformally mapped to a parallelogram. The resulting surface subdivision and the parameterizations of the components are intrinsic and stable (their solutions tend to be smooth functions and the boundary conditions of the Dirichlet problem can be enforced). Conformal parameterization also helps transform partial differential equations (PDEs) that may be defined on 3-D brain surface manifolds to modified PDEs on a two-dimensional parameter domain. Since the Jacobian matrix of a conformal parameterization is diagonal, the modified PDE on the parameter domain is readily solved. To illustrate our techniques, we computed parameterizations for several types of anatomical surfaces in 3-D magnetic resonance imaging scans of the brain, including the cerebral cortex, hippocampi, and lateral ventricles. For surfaces that are topologically homeomorphic to each other and have similar geometrical structures, we show that the parameterization results are consistent and the subdivided surfaces can be matched to each other. Finally, we present an automatic sulcal landmark location algorithm by solving PDEs on cortical surfaces. The landmark detection results are used as constraints for building conformal maps between surfaces that also match explicitly defined landmarks. PMID:17679336

  17. Intrinsic Structure, Surface Properties, and Dissociation Reactions on Metal Surfaces. (United States)

    Liyanage, Lalantha Saman

    The original Surface Embedded Green Function (SEGF) method has been used to perform self-consistent calculations of the surface electronic structure of (1x1)Pt(001), O/Pt(001) and (1x5)Pt(001). Calculated work functions, surface state and surface resonance bands, and densities of states are compared with experiment and with earlier slab calculations. The calculated work function for all three surfaces is in excellent agreement with experiment. In general, other results are also consistent with experiment. Total and difference charge density plots are used to illustrate details of O-Pt bonding. Analysis of the surface charge density of (1x1)Pt(001) shows an increase in sp bonding charge which leads to a compressive surface stress, and may help explain the surface reconstruction. The stress is reduced in the O/Pt(001) surface, indicating oxygen stabilization of the (1x1) phase. The calculated difference-DOS curve between (1x1)Pt(001) and (1x5)Pt(001) reveals a reduction of the DOS near the Fermi level for the (1x5) phase, which helps explain the low chemical activity of the reconstructed surface. The method of removing the two-dimensional inversion symmetry requirement from the original SEGF technique is discussed in detail. The generalized SEGF method is tested by applying it to the Al(111) surface. The results obtained by the study are in excellent agreement with experiment and with slab calculations.

  18. Star points on cubic surfaces

    NARCIS (Netherlands)

    Nguyen, T.C.


    A cubic surface in P 3 is given by a non-zero cubic homogeneous polynomial in 4 variables. Fixing an ordering of monomials of degree 3 in the polynomial ring k[x0; x1; x2; x3 ], each cubic surface denes a point in P 19 . The locus P 19 of singular cubic surfaces is a closed subset of

  19. Surface Effects in Magnetic Nanoparticles

    CERN Document Server

    Fiorani, Dino


    This volume is a collection of articles on different approaches to the investigation of surface effects on nanosized magnetic materials, with special emphasis on magnetic nanoparticles. The book aims to provide an overview of progress in the understanding of surface properties and surface driven effects in magnetic nanoparticles through recent results of different modeling, simulation, and experimental investigations.

  20. Surface chemical modification of nanocrystals (United States)

    Helms, Brett Anthony; Milliron, Delia Jane; Rosen, Evelyn Louise; Buonsanti, Raffaella; Llordes, Anna


    Nanocrystals comprising organic ligands at surfaces of the plurality of nanocrystals are provided. The organic ligands are removed from the surfaces of the nanocrystals using a solution comprising a trialkyloxonium salt in a polar aprotic solvent. The removal of the organic ligands causes the nanocrystals to become naked nanocrystals with cationic surfaces.

  1. Emerging trends in surface metrology

    DEFF Research Database (Denmark)

    Lonardo, P.M.; Lucca, D.A.; De Chiffre, Leonardo


    Recent advancements and some emerging trends in the methods and instruments used for surface and near surface characterisation are presented, considering the measurement of both topography and physical properties. In particular, surfaces that present difficulties in measurement or require new pro...

  2. SDL: A Surface Description Language (United States)

    Maple, Raymond C.


    A new interpreted language specifically designed for surface grid generation is introduced. Many unique aspects of the language are discussed, including the farray, vector, curve, and surface data types and the operators used to manipulate them. Custom subroutine libraries written in the language are used to easily build surface grids for generic missile shapes.


    The problem of the construction of a Hamiltonian formalism suitable for propagation of a field off characteristic or null surfaces is considered. developed on characteristic surfaces. A Hamiltonian for gravitation (general relativity) is constructed, first on null surfaces described only by

  4. The surface energy of metals

    DEFF Research Database (Denmark)

    Vitos, Levente; Ruban, Andrei; Skriver, Hans Lomholt


    We have used density functional theory to establish a database of surface energies for low index surfaces of 60 metals in the periodic table. The data may be used as a consistent starting point for models of surface science phenomena. The accuracy of the database is established in a comparison...

  5. Surface plasmon polariton waveguiding in random surface nanostructures

    DEFF Research Database (Denmark)

    Bozhevolnyi, S. I.; Volkov, V. S.; Leosson, K.


    In this study, guiding of surface plasmon polaritons excited at a gold film surface along corrugation-free channels in regions that are covered with randomly located surface scatterers, is considered using near-field microscopy for imaging of surface plasmon polariton intensity distributions...... at the surface. In the wavelength range 713-815 nm, we observed complete inhibition of the surface plasmon polariton propagation inside the random structures composed of individual (approx. 70 nm high) gold bumps (and their clusters) placed on a 55 nm thick gold film with a bump density of 75 micro-m-2. We...... demonstrate well-defined surface plasmon polariton guiding along corrugation-free 2 micro-m wide channels in random structures and, in the wavelength range 738-774 nm, low-loss guiding around 20degrees bends having a bend radius of approx. 15 micro-m....

  6. Preface: Oxide Surfaces (United States)

    Willmott, Phil


    Although the history of metal oxides and their surfaces goes back several decades to landmark studies, such as Mott and Peierls' explanation of electrical insulation in materials that are predicted in band theory to be conducting, or the observation by Morin of the superfast metal-to-insulator transition in vanadium dioxide, it is only in the last two decades that the world of condensed matter physics has become increasingly dominated by research into complex metal oxides. This has been driven most notably by an attempt to better understand and describe the fundamental physical processes behind their seemingly endless spectrum of properties, which in turn has also led to the discovery of novel phenomena, most prominently demonstrated by the discovery of high-temperature superconductivity in 1986, colossal magnetoresistance in 1994, and most recently, the formation of a two-dimensional conducting layer at the interface between two band insulators in 2004. One important reason why metal oxides, particularly in the form of thin films, have become such a popular subject for basic condensed matter research is that they offer a uniquely versatile materials base for the development of novel technologies. They owe this versatility both to the many different elemental combinations that lead to structurally similar forms, and also to the fact that in many cases, the strong interaction between the valence electrons means that there is a subtle interplay between structure and magnetic and electronic properties. This aspect has led in recent years to the birth or renaissance of research fields such as spintronics, orbital ordering, and multiferroics. Surfaces and interfaces are especially interesting in these strongly-correlated electron systems, where the rearrangement of electrical charge resulting from a minimization of surface or interfacial energy can have unexpected and often exciting consequences. Indeed, as the drive to miniaturize devices well below the micron size

  7. Surface Temperature Data Analysis (United States)

    Hansen, James; Ruedy, Reto


    Small global mean temperature changes may have significant to disastrous consequences for the Earth's climate if they persist for an extended period. Obtaining global means from local weather reports is hampered by the uneven spatial distribution of the reliably reporting weather stations. Methods had to be developed that minimize as far as possible the impact of that situation. This software is a method of combining temperature data of individual stations to obtain a global mean trend, overcoming/estimating the uncertainty introduced by the spatial and temporal gaps in the available data. Useful estimates were obtained by the introduction of a special grid, subdividing the Earth's surface into 8,000 equal-area boxes, using the existing data to create virtual stations at the center of each of these boxes, and combining temperature anomalies (after assessing the radius of high correlation) rather than temperatures.

  8. Front Surface Pyrometer. (United States)


    is too high. Thus, the DPI series is for glass surface temperature measurement: the GPI has a minimum temperature 450’C so that paper and wood etc...0.60 0.80 sillimanite 0.60 0.60 0.60 Ceramics 0.40 0.50 0.90 Magnesite 0.60 B-9 Table B-1. Table of emissivities for Land GP series weave reduces emissivity Glass 3 mm thick 096 0.72 6 mm thick 0.96 0.90 12 mm thick 0.96 095 20 mm thick 0.96 0.96 Paper & Cardboard 0.8- 0.95

  9. Surface enhanced thermo lithography

    KAUST Repository

    Coluccio, Maria Laura


    We used electroless deposition to fabricate clusters of silver nanoparticles (NPs) on a silicon substrate. These clusters are plasmonics devices that induce giant electromagnetic (EM) field increments. When those EM field are absorbed by the metal NPs clusters generate, in turn, severe temperature increases. Here, we used the laser radiation of a conventional Raman set-up to transfer geometrical patterns from a template of metal NPs clusters into a layer of thermo sensitive Polyphthalaldehyde (PPA) polymer. Temperature profile on the devices depends on specific arrangements of silver nanoparticles. In plane temperature variations may be controlled with (i) high nano-meter spatial precision and (ii) single Kelvin temperature resolution on varying the shape, size and spacing of metal nanostructures. This scheme can be used to generate strongly localized heat amplifications for applications in nanotechnology, surface enhanced thermo-lithography (SETL), biology and medicine (for space resolved cell ablation and treatment), nano-chemistry.

  10. Hydrological land surface modelling

    DEFF Research Database (Denmark)

    Ridler, Marc-Etienne Francois

    Recent advances in integrated hydrological and soil-vegetation-atmosphere transfer (SVAT) modelling have led to improved water resource management practices, greater crop production, and better flood forecasting systems. However, uncertainty is inherent in all numerical models ultimately leading...... and disaster management. The objective of this study is to develop and investigate methods to reduce hydrological model uncertainty by using supplementary data sources. The data is used either for model calibration or for model updating using data assimilation. Satellite estimates of soil moisture and surface...... hydrological and tested by assimilating synthetic hydraulic head observations in a catchment in Denmark. Assimilation led to a substantial reduction of model prediction error, and better model forecasts. Also, a new assimilation scheme is developed to downscale and bias-correct coarse satellite derived soil...

  11. The surface learned from nature (United States)

    Lim, H.; Kim, W. D.


    In this work, I would like to introduce the emerging surface of nature. The surface in nature, has the multi and optimized function with well organized structure. There are so many examples that we learn and apply to technology. First example is self-cleaning surface. Some plants (such as lotus leaf, taro leaf) and the wings of many large-winged insects (such as moth, butterfly, dragonfly) remain their surface clean in the very dirty environment. This self cleaning effect is accomplished by the superhydrophobic surfaces which exhibit the water contact angle of more than 150° with low sliding angle. Generally, the superhydrophobic surface is made up the two factors. One is the surface composition having the low surface tension energy. The other is the surface morphology of hierarchical structure of micro and nano size. Because almost nature surface have the hierarchical structures range from macro to nano size, their topography strength their function to adjust the life in nature environment. The other example is the surface to use for drag reduction. The skin friction drag causes eruptions of air or water resulting in greater drag as the speed is increased. This drag requires more energy to overcome. The shark skin having the fine sharp-edged grooves about 0.1 mm wide known riblet reduces in skin friction drag by being far away the vortex. Among a lot of fuctional surface, the most exciting surface the back of stenocara a kind of desert beetles. Stenocara use the micrometre-sized patterns of hydrophobic, wax-coated and hydrophilic, non-waxy regions on their backs to capture water from fog. This fog-collecting structure improves the water collection of fog-capture film, condenser, engine, and future building. Here, the efforts to realize these emerging functional surfaces in nature on technology are reported with the fabrication method and their properties, especially for the control of surface wettability.

  12. Surface-stabilized gold nanocatalysts (United States)

    Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN


    A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

  13. Peano high-impedance surfaces (United States)

    McVay, John; Hoorfar, Ahmad; Engheta, Nader


    Following our previous work on metamaterial high-impedance surfaces made of Hilbert curve inclusions, here we theoretically explore the performance of the high-impedance surfaces made of another form of space-filling curve known as the Peano curve. This metamaterial surface, formed by a two-dimensional periodic arrangement of Peano curve inclusions, is located above a conducting ground plane and is shown to exhibit a high surface impedance at certain specific frequencies. Our numerical study reveals the effect of the iteration order of the Peano curve, the surface height above the conducting ground plane, and the separation distance between adjacent inclusions.

  14. Rectification of nanopores at surfaces. (United States)

    Sa, Niya; Baker, Lane A


    At the nanoscale, methods to measure surface charge can prove challenging. Herein we describe a general method to report surface charge through the measurement of ion current rectification of a nanopipette brought in close proximity to a charged substrate. This method is able to discriminate between charged cationic and anionic substrates when the nanopipette is brought within distances from ten to hundreds of nanometers from the surface. Further studies of the pH dependence on the observed rectification support a surface-induced mechanism and demonstrate the ability to further discriminate between cationic and nominally uncharged surfaces. This method could find application in measurement and mapping of heterogeneous surface charges and is particularly attractive for future biological measurements, where noninvasive, noncontact probing of surface charge will prove valuable.

  15. Approximation of Surfaces by Cylinders

    DEFF Research Database (Denmark)

    Randrup, Thomas


    We present a new method for approximation of a given surface by a cylinder surface. It is a constructive geometric method, leading to a monorail representation of the cylinder surface. By use of a weighted Gaussian image of the given surface, we determine a projection plane. In the orthogonal...... projection of the surface onto this plane, a reference curve is determined by use of methods for thinning of binary images. Finally, the cylinder surface is constructed as follows: the directrix of the cylinder surface is determined by a least squares method minimizing the distance to the points...... in the projection within a tolerance given by the reference curve, and the rulings are lines perpendicular to the projection plane. Application of the method in ship design is given....

  16. Polaron-Driven Surface Reconstructions (United States)

    Reticcioli, Michele; Setvin, Martin; Hao, Xianfeng; Flauger, Peter; Kresse, Georg; Schmid, Michael; Diebold, Ulrike; Franchini, Cesare


    Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy) to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1 ×1 ) to (1 ×2 ) transition in rutile TiO2 (110 ) .

  17. Polaron-Driven Surface Reconstructions

    Directory of Open Access Journals (Sweden)

    Michele Reticcioli


    Full Text Available Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1×1 to (1×2 transition in rutile TiO_{2}(110.

  18. Helium atom scattering from surfaces

    CERN Document Server


    High resolution helium atom scattering can be applied to study a number of interesting properties of solid surfaces with great sensitivity and accuracy. This book treats in detail experimental and theoretical aspects ofthis method as well as all current applications in surface science. The individual chapters - all written by experts in the field - are devoted to the investigation of surface structure, defect shapes and concentrations, the interaction potential, collective and localized surface vibrations at low energies, phase transitions and surface diffusion. Over the past decade helium atom scattering has gained widespread recognitionwithin the surface science community. Points in its favour are comprehensiveunderstanding of the scattering theory and the availability of well-tested approximation to the rigorous theory. This book will be invaluable to surface scientists wishing to make an informed judgement on the actual and potential capabilities of this technique and its results.

  19. Growth of gallium nitride based devices on silicon(001) substrates by metalorganic vapor phase epitaxy; Wachstum von Galliumnitrid-basierten Bauelementen auf Silizium(001)-Substraten mittels metallorganischer Gasphasenepitaxie

    Energy Technology Data Exchange (ETDEWEB)

    Reiher, Fabian


    The main topic of this thesis is to investigate GaN-based layer systems grown by metalorganic vapor phase epitaxy on Si(001) substrates. A temperature shift up to 45 K is measured for a complete device structure on a 2-inch silicon substrate. By using a 40 nm thin LT-AlN-seed layer (680 C), the GaN crystallites on Si(001) substrates are almost oriented with their GaN(10 anti 12)-planes parallel to the Si(001)-plane. A four-fold azimuthal symmetry occurs for these layers, with the GaN[10 anti 11]-direction is aligned parallel to one of the four equivalent left angle 110 right angle -directions, respectively. However, a mono-crystalline and fully coalesced GaN-layer with this crystallographic orientation could not yet been obtained. If a deposition temperature of more than 1100 C is used for the AlN-seed layer, solely the GaN[0001]- growth direction of crystallites occurs in the main GaN layer on Si(001) substrates. These c-axis oriented GaN columns feature two opposite azimuthal alignments that are rotated by 90 with respect to each other and with GaN[11 anti 20] parallel Si[110] and GaN[10 anti 10] parallel Si[110], respectively. By using 4 off-oriented substrates towards the Si[110]-direction, one certain azimuthal texture component can be selected. The critical value of the miscut angle corresponds to theoretical calculations predicting the occurrence of atomic double steps on the Si(001) surface. The achieved crystallographic quality of the GaN layers on Si(001) is characterized by having a tilt of FWHM=0.27 and a twist of FWHM=0.8 of the crystallites, determined by X-ray diffraction. A completely crack-free, up to 2.5 {mu}m thick, and mono-crystalline GaN-template can be realized on Si(001), integrating 4 or 5 LT-AlN-interlayers in the GaN buffer structure. Based on this structure, the first successful implementation of an (InGaN/GaN)-LED on Si(001) is achieved. Furthermore, the possible fabrication of GaN-based FET-structures is demonstrated with a fully

  20. Occupied and unoccupied electronic states on vicinal Si(111) surfaces decorated with monoatomic gold chains; Besetzte und unbesetzte elektronische Zustaende vizinaler Si(111)-Oberflaechen mit atomaren Goldketten

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Kerstin


    -dimensional gold chains, spin-polarized silicon atoms at the step edges, which are coupled anti-ferromagnetically. This leads to the occurrence of intrinsic magnetism on a non-magnetic material. The related strongly localized states could be detected experimentally in both the occupied and the unoccupied part of the band structure for the very first time and therefore their existence is confirmed. All these surfaces resemble each other with respect to the n=1 image-potential resonance, which is excited from initial states of even and odd parity. The negative dispersion of this state in the direction along the chains with an effective mass in the range of the mass of the light-hole valence-band maximum is particularly noteworthy. In conjunction with the photon-energy dependence this leads to the assumption that the dispersion of the image-potential resonances is dominated by the initial states from which they are excited. Their lifetimes of 10 fs to 20 fs resemble the lifetime of the image-potential resonance on Si(001). A further analogy regarding the dynamics of the Si(111)-Au surfaces is the occurrence of intensity for UV-pump-IR-probe processes in a range of one to one and a half electron volts below the vacuum energy. Within this range there is no clear evidence for intermediate states, to which lifetimes - decreasing with their distance from the vacuum level - of several tens of femtoseconds could be attributed. For this phenomenon no final explanation could be found. The most interesting part of the complex carrier dynamics on the Si(111)-Au surfaces, however, takes place inside the bulk band gap of silicon. On all these surfaces there is at least one strongly localized surface state with a lifetime between 80 fs and 150 fs inside the bulk band gap. This intermediate state is not only populated by an IR-pump process, but also filled via surface recombination. This additional population takes place on a timescale of several hundreds of femtoseconds or even one picosecond

  1. Adhesion energy, surface traction and surface tension in liquid xenon

    Indian Academy of Sciences (India)

    Abstract. We calculated the adhesion energy, the surface traction and the surface energy of liquid xenon using molecular dynamics (MD) simulation. The value of the adhesion energy for liquid xenon at a reduced density of 0.630 was found to be 0.591 J/m2 and the surface traction has a peak at z = 3.32 Å. It was observed ...

  2. Surface Energy and Setting Process of Contacting Surfaces

    Directory of Open Access Journals (Sweden)

    M. V. Musokhranov


    Full Text Available The paper deals with a challenge in terms of ensuring an accuracy of the relative position of the conjugated surfaces that is to determine a coefficient of friction. To solve it, there is a proposal to use the surface energy, as a tool that influences the contacting parts nature. Presently, energy of the surface layers at best is only stated, but not used in practice.Analysis of the conditions of interaction between two contacting surfaces, such as seizing and setting cannot be explained only from the position of the roughness parameters. It is found that these phenomena are explained by the appearing gripe (setting bridges, which result from the energy of interaction between two or more adjacent surfaces. The emerging phenomenon such as micro welding, i.e. occurring bonds, is caused by the overflow of energy, according to the theory of physics, from the surface with a high level of energy to the surface with the smaller one to balance the system as a whole.The paper shows that through the use of process, controlling the depth of the surface layer and creating a certain structure, the energy level of the material as a whole can be specified. And this will allow us to provide the necessary performance and mechanical properties. It means to create as many gripe bridges as possible to ensure continuous positioning i.e. a fixed connection of the contacting surfaces.It was determined that to increase a value of the friction coefficient, the physical and mechanical properties of the surface layer of the parts material must be taken into account, namely, in the part body accumulate the energy to be consumed for forming the surface.The paper gives recommendations for including the parts of the surface energy in the qualitative indicators of characteristics. This will make a technologist, when routing a process, to choose such operations and modes to provide the designer-specified parameters not only of the accuracy and surface finish, but also of the

  3. Magnetotransport, structural and optical characterization of p-type modulation doped heterostructures with high Ge content Si sub 1 sub - sub x Ge sub x channel grown by SS-MBE on Si sub 1 sub - sub y Ge sub y /Si(001) virtual substrates

    CERN Document Server

    Myronov, M


    sub 4 Ge sub 0 sub . sub 6 linearly graded VS and corresponds to 14855cm sup 2 centre dot V sup - sup 1 centre dot s sup - sup 1 (2.87 centre dot 10 sup 1 sup 2 cm sup - sup 2). The highest Hall mobility (at sheet carrier density) measured at 293K was observed for Si sub 0 sub . sub 2 Ge sub 0 sub . sub 8 /Si sub 0 sub . sub 6 sub 5 Ge sub 0 sub . sub 3 sub 5 heterostructure after FTA at 750C for 30min and corresponds to 1776cm sup 2 centre dot V sup - sup 1 centre dot s sup - sup 1 (2.37 centre dot 10 sup 1 sup 3 cm sup - sup 2). To extract the drift mobility and sheet carrier density of 2DHG at temperatures up to 300K, magnetotransport measurements in magnetic fields up to 11T were performed on several heterostructures. The data were analyzed by technique of Maximum-Entropy Mobility Spectrum Analysis. The highest drift mobility (at sheet carrier density) of 2DHG at 290K was obtained for the Si sub 0 sub . sub 2 Ge sub 0 sub . sub 8 /Si sub 0 sub . sub 6 sub 5 Ge sub 0 sub . sub 3 sub 5 heterostructure after...

  4. Atom-specific surface magnetometry (United States)

    Sirotti, Fausto; Panaccione, Giancarlo; Rossi, Giorgio


    A powerful atom-specific surface magnetometry can be based on efficient measurements of magnetic dichroism in l>~0 core level photoemission. The temperature dependence M(T) of the Fe(100) surface magnetization was obtained from the photoemission magnetic asymmetry of 3p core levels, providing the measure of the surface exchange coupling via the spin-wave stiffness and of the surface critical exponent. Beyond the magnetic order the photoemission dichroism allows us to derive the energy splitting of the magnetic sublevels of the photoexcited core hole. Fe 3p photoemission dichroism probes directly the magnetic moment changes of iron atoms at Fe(100) surfaces as a function of structural disorder or sulfur segregation. The appearance of dichroism in the 2p photoemission of segregated sulfur atoms in the c(2×2)S/Fe(100) superstructure measures the magnetic-moment transfer and shows the possibility of investigating surface magnetochemistry in a very direct way.

  5. Undergraduate Laboratory for Surface Science (United States)

    Okumura, Mitchio; Beauchamp, Jesse L.; Dickert, Jeffrey M.; Essy, Blair R.; Claypool, Christopher L.


    Surface science has developed into a multidisciplinary field of research with applications ranging from heterogeneous catalysis to semiconductor etching (1). Aspects of surface chemistry are now included in physical chemistry textbooks (2) and undergraduate curricula (3), but the perceived cost and complexity of equipment has deterred the introduction of surface science methods in undergraduate laboratories (4). Efforts to expose chemistry undergraduates to state-of-the-art surface instrumentation have just begun (5). To provide our undergraduates with hands-on experience in using standard techniques for characterizing surface morphology, adsorbates, kinetics, and reaction mechanisms, we have developed a set of surface science experiments for our physical chemistry laboratory sequence. The centerpiece of the laboratory is an ultrahigh vacuum (UHV) chamber for studies of single crystal surfaces. This instrument, shown in the figure, has surface analysis capabilities including low energy electron diffraction (LEED), Auger spectroscopy, and temperature-programmed desorption (TPD). The laboratory exercises involve experiments on the well-studied Pt(111) surface. Students prepare a previously mounted single crystal sample by sputtering it with an argon ion gun and heating it under O2. Electron diffraction patterns from the cleaned surface are then obtained with a reverse view LEED apparatus (Princeton Instruments). Images are captured by a charge-coupled device (CCD) camera interfaced to a personal computer for easy downloading and subsequent analysis. Although the LEED images from a Pt(111) surface can be readily interpreted using simple diffraction arguments, this lab provides an excellent context for introducing Miller indices and reciprocal lattices (6). The surface chemical composition can be investigated by Auger spectroscopy, using the LEED apparatus as a simple energy analyzer. The temperature programmed desorption experiment, which is nearly complete, will be

  6. Friction surfaced Stellite6 coatings

    Energy Technology Data Exchange (ETDEWEB)

    Rao, K. Prasad; Damodaram, R. [Department of Metallurgical and Materials Engineering - Indian Institute of Technology Madras, Chennai 600 036 (India); Rafi, H. Khalid, E-mail: [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Ram, G.D. Janaki [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Reddy, G. Madhusudhan [Metal Joining Group, Defence Metallurgical Research Laboratory (DMRL) Kanchanbagh, Hyderabad 500 058 (India); Nagalakshmi, R. [Welding Research Institute, Bharat Heavy Electricals Limited, Tiruchirappalli 620 014 (India)


    Solid state Stellite6 coatings were deposited on steel substrate by friction surfacing and compared with Stellite6 cast rod and coatings deposited by gas tungsten arc and plasma transferred arc welding processes. Friction surfaced coatings exhibited finer and uniformly distributed carbides and were characterized by the absence of solidification structure and compositional homogeneity compared to cast rod, gas tungsten arc and plasma transferred coatings. Friction surfaced coating showed relatively higher hardness. X-ray diffraction of samples showed only face centered cubic Co peaks while cold worked coating showed hexagonally close packed Co also. - Highlights: Black-Right-Pointing-Pointer Stellite6 used as coating material for friction surfacing. Black-Right-Pointing-Pointer Friction surfaced (FS) coatings compared with casting, GTA and PTA processes. Black-Right-Pointing-Pointer Finer and uniformly distributed carbides in friction surfaced coatings. Black-Right-Pointing-Pointer Absence of melting results compositional homogeneity in FS Stellite6 coatings.

  7. Surface Detection using Round Cut

    DEFF Research Database (Denmark)

    Dahl, Vedrana Andersen; Dahl, Anders Bjorholm; Larsen, Rasmus


    similar adaptations for triangle meshes, our method is capable of capturing complex geometries by iteratively refining the surface, where we obtain a high level of robustness by applying explicit mesh processing to intermediate results. Our method uses on-surface data support, but it also exploits data......We propose an iterative method for detecting closed surfaces in a volumetric data, where an optimal search is performed in a graph build upon a triangular mesh. Our approach is based on previous techniques for detecting an optimal terrain-like or tubular surface employing a regular grid. Unlike...... information about the region inside and outside the surface. This provides additional robustness to the algorithm. We demonstrate the capabilities of the approach by detecting surfaces of CT scanned objects....

  8. Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces

    DEFF Research Database (Denmark)

    González, Alejandro González; Hemmsen, Martin Christian; Wilhjelm, Jens E.


    Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces......Assessment of flatness of assumed planar surfaces for ultrasound investigation of elastic surfaces...

  9. The surface charge of trypanosomatids

    Directory of Open Access Journals (Sweden)



    Full Text Available The surface charge of trypanosomatids was evaluated by means of the binding of cationic particles, as visualized by electron microscopy and by direct measurements of the electrophoretic mobility of cells. The results obtained indicate that most of the trypanosomatids exhibit a negatively charged surface whose value is species specific and varies according to the developmental stages. Sialic acids associated with glycoproteins, glycolipids and phosphate groups are the major components responsible for the net negative surface charge of the trypanosomatids.

  10. How old is surface science?

    Energy Technology Data Exchange (ETDEWEB)

    Paparazzo, E. E-mail:


    Philosophical and literary testimonies from the Classical World (5th century B.C. to 3rd century A.D.) involving solid surfaces are reviewed. Plato thought the surface to be a real entity, whereas Aristotle considered it to possess an unqualified existence, i.e. not to be a substance, but just an accidental entity. The Old Stoics asserted that surfaces do not possess any physical existence, although the Stoic philosopher Posidonius--apparently the only exception in his school--held them to exist both in thought and reality. While both the Atomists and the Epicureans were very little interested in them, the Sceptic philosopher Sextus Empiricus considered surfaces to be the limits of a body, although he maintained that both the view that they are corporeal or the view that they are incorporeal present unsurmountable difficulties. Among Roman authors, the testimony from Pliny the Elder is mostly concerned with metallic surfaces, chemical change occurring there, and surface treatments used in antiquity. Besides the philosophical motivations, the implications of the testimonies are discussed in the light of surface science. The purely geometrical surface of Plato is found to compare favorably to single-crystal surface, Posidonius' 'corporeal' surface is best likened to an air-oxidized, or otherwise ambient-modified surface, and ancient accounts on mixture are compared to XPS results obtained in adhesion studies of enameled steels. I argue that the long-standing dominance of Aristotle's view from antiquity onwards may have had a part in delaying theoretical speculation into solid surfaces.

  11. Catalytic Reactions on Model Gold Surfaces: Effect of Surface Steps and of Surface Doping

    Directory of Open Access Journals (Sweden)

    Maria Natália D. S. Cordeiro


    Full Text Available The adsorption energies and the activation energy barriers for a series of reactions catalyzed by gold surfaces and obtained theoretically through density functional theory (DFT based calculations were considered to clarify the role of the low coordinated gold atoms and the role of doping in the catalytic activity of gold. The effect of the surface steps was introduced by comparison of the activation energy barriers and of the adsorption energies on flat gold surfaces such as the Au(111 surface with those on stepped surfaces such as the Au(321 or the Au(110 surfaces. It is concluded that the presence of low coordinated atoms on the latter surfaces increases the adsorption energies of the reactants and decreases the activation energy barriers. Furthermore, the increasing of the adsorption energy of the reaction products can lead to lower overall reaction rates in the presence of low gold coordinated atoms due to desorption limitations. On the other hand, the effect of doping gold surfaces with other transition metal atoms was analyzed using the dissociation reaction of molecular oxygen as a test case. The calculations showed that increasing the silver content in some gold surfaces was related to a considerable increment of the reactivity of bimetallic systems toward the oxygen dissociation. Importantly, that increment in the reactivity was enhanced by the presence of low coordinated atoms in the catalytic surface models considered.

  12. General investigations of curved surfaces

    CERN Document Server

    Gauss, Karl Friedrich; Morehead, James


    Gauss's theory of surfaces is among the purely mathematical achievements inspired by ideas that arose in connection with surveys of the surface of the earth. Long regarded as a masterpiece in content and form, this work features one of the author's most original contributions to mathematics--the discovery that Gauss termed the ""Theorema Egregium."" It consists of his penetrating definition of the concept of surface curvature and the theorem that the ""Gauss curvature"" is invariant under arbitrary isometric deformation of a curved surface. The profound effects of these concepts were soon gene

  13. Rectangular diagrams of surfaces: representability (United States)

    Dynnikov, I. A.; Prasolov, M. V.


    Introduced here is a simple combinatorial way, which is called a rectangular diagram of a surface, to represent a surface in the three-sphere. It has a particularly nice relation to the standard contact structure on S^3 and to rectangular diagrams of links. By using rectangular diagrams of surfaces it is intended, in particular, to develop a method to distinguish Legendrian knots. This requires a lot of technical work of which the present paper addresses only the first basic question: which isotopy classes of surfaces can be represented by a rectangular diagram? Roughly speaking, the answer is this: there is no restriction on the isotopy class of the surface, but there is a restriction on the rectangular diagram of the boundary link arising from the presentation of the surface. The result extends to Giroux's convex surfaces for which this restriction on the boundary has a natural meaning. In a subsequent paper, transformations of rectangular diagrams of surfaces will be considered and their properties will be studied. By using the formalism of rectangular diagrams of surfaces an annulus in S^3 is produced here that is expected to be a counterexample to the following conjecture: if two Legendrian knots cobound an annulus and have zero Thurston-Bennequin numbers relative to this annulus, then they are Legendrian isotopic. Bibliography: 30 titles.

  14. Radioactive Probes on Ferromagnetic Surfaces

    CERN Document Server


    On the (broad) basis of our studies of nonmagnetic radioactive probe atoms on magnetic surfaces and at interfaces, we propose to investigate the magnetic interaction of magnetic probe atoms with their immediate environment, in particular of rare earth (RE) elements positioned on and in ferromagnetic surfaces. The preparation and analysis of the structural properties of such samples will be performed in the UHV chamber HYDRA at the HMI/Berlin. For the investigations of the magnetic properties of RE atoms on surfaces Perturbed Angular Correlation (PAC) measurements and Mössbauer Spectroscopy (MS) in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN) are proposed.

  15. Are Vicinal Metal Surfaces Stable?

    DEFF Research Database (Denmark)

    Frenken, J. W. M.; Stoltze, Per


    We use effective medium theory to demonstrate that the energies of many metal surfaces are lowered when these surfaces are replaced by facets with lower-index orientations. This implies that the low-temperature equilibrium shapes of many metal crystals should be heavily faceted. The predicted ins...... instability of vicinal metal surfaces is at variance with the almost generally observed stability of these surfaces. We argue that the unstable orientations undergo a defaceting transition at relatively low temperatures, driven by the high vibrational entropy of steps....

  16. Surface composition and surface properties of water hyacinth ...

    African Journals Online (AJOL)



    Oct 26, 2015 ... The surface composition and surface properties of water hyacinth (Eichhornia crassipes) root biomass were studied before and after extraction with dilute nitric acid and toluene/ethanol (2/1, v/v) followed by ethanol, using Fourier Transform Infra-red (FT-IR) spectroscopy, thermogravimetric analysis, x-ray.

  17. Surface photometry of bulge dominated low surface brightness galaxies

    NARCIS (Netherlands)

    Beijersbergen, M; de Blok, WJG; van der Hulst, JM


    We present results of broad band BVRI observations of a sample of galaxies with a low surface brightness (LSB) disk and a bulge. These galaxies are well described as exponential disks and exponential bulges with no preferred value for either scale length or central surface brightness. The median B

  18. Surface-to-surface registration using level sets

    DEFF Research Database (Denmark)

    Hansen, Mads Fogtmann; Erbou, Søren G.; Vester-Christensen, Martin


    This paper presents a general approach for surface-to-surface registration (S2SR) with the Euclidean metric using signed distance maps. In addition, the method is symmetric such that the registration of a shape A to a shape B is identical to the registration of the shape B to the shape A. The S2S...

  19. Polygon formation and surface flow on a rotating fluid surface

    DEFF Research Database (Denmark)

    Bergmann, Raymond; Tophøj, Laust Emil Hjerrild; Homan, T. A. M.


    'wet' or with a 'dry' centre. For the dry structures, we present measurements of the surface shapes and the process of formation. We show experimental evidence that the formation can take place as a two-stage process: first the system approaches an almost stable rotationally symmetric state and from......, we measure the surface flows by particle image velocimetry (PIV) and show that there are three vortices present, but that the strength of these vortices is far too weak to account for the rotation velocity of the polygon. We show that partial blocking of the surface flow destroys the polygons and re......-establishes the rotational symmetry. For the rotationally symmetric state our theoretical analysis of the surface flow shows that it consists of two distinct regions: an inner, rigidly rotating centre and an outer annulus, where the surface flow is that of a point vortex with a weak secondary flow. This prediction...

  20. Interactive Display of Surfaces Using Subdivision Surfaces and Wavelets

    Energy Technology Data Exchange (ETDEWEB)

    Duchaineau, M A; Bertram, M; Porumbescu, S; Hamann, B; Joy, K I


    Complex surfaces and solids are produced by large-scale modeling and simulation activities in a variety of disciplines. Productive interaction with these simulations requires that these surfaces or solids be viewable at interactive rates--yet many of these surfaced solids can contain hundreds of millions of polygondpolyhedra. Interactive display of these objects requires compression techniques to minimize storage, and fast view-dependent triangulation techniques to drive the graphics hardware. In this paper, we review recent advances in subdivision-surface wavelet compression and optimization that can be used to provide a framework for both compression and triangulation. These techniques can be used to produce suitable approximations of complex surfaces of arbitrary topology, and can be used to determine suitable triangulations for display. The techniques can be used in a variety of applications in computer graphics, computer animation and visualization.

  1. Modifying surface forces through control of surface potentials. (United States)

    Tivony, Ran; Klein, Jacob


    Combining direct surface force measurements with in situ regulation of surface potential provides an exceptional opportunity for investigating and manipulating interfacial phenomena. Recently, we studied the interaction between gold and mica surfaces in water with no added salt, while controlling the metal potential, and found that the surface charge at the metal may vary, and possibly even change its sign, as it progressively approaches the (constant-charge) mica surface [Langmuir, 2015, 31(47), 12845-12849]. Such a variation was found to directly affect the nature of the contact and adhesion between them due to exclusion of all mobile counterions from the intersurface gap. In this work, we extend this to examine the potential-dependent response of the adhesion and interaction between gold and mica to externally applied voltages and in electrolyte solution. Using a surface force balance (SFB) combined with a three-electrode electrochemical cell, we measured the normal interaction between gold and mica under surface potential regulation, revealing three interaction regimes - pure attraction, non-monotonic interaction from electrostatic repulsion to attraction (owing to charge inversion) and pure repulsion. Accordingly, the adhesion energy between the surfaces was found to vary both in no added salt water and, more strongly, in electrolyte solution. We justify this potential-dependent variation of adhesion energy in terms of the interplay between electrostatic energy and van der Waals (vdW) interaction at contact, and attribute the difference between the two cases to the weaker vdW interaction in electrolyte solution. Finally, we showed that through abruptly altering the gold surface potential from negative to positive and vice versa, the adhesion between gold and mica can be reversibly switched on and off. We surmise that the process of bringing the surface into contact is associated with the formation of a strong electric field O (10 8 V m -1 ) in the intersurface

  2. Interference effects with surface plasmons

    NARCIS (Netherlands)

    Kuzmin, Nikolay Victorovich


    A surface plasmon is a purely two-dimensional electromagnetic excitation bound to the interface between metal and dielectric and quickly decaying away from it. A surface plasmon is able to concentrate light on sub-wavelength scales – a feature that is attractive for nano-photonics and integrated

  3. Surface tension of aqueous humor. (United States)

    Ross, Andrew; Blake, Robert C; Ayyala, Ramesh S


    To measure and compare the surface tension of aqueous humor in patients with and without glaucoma. The surface tension of aqueous humor was measured using a commercially available instrument and software that were validated by using a known fluid (deionized water and methanol). Analysis of aqueous and vitreous samples obtained from 20 rabbit eyes showed that the system could be used successfully for small amounts of ocular fluid. The effect of glaucoma drugs on the surface tension of aqueous humor was then studied in a rabbit model. Comparison of aqueous humor from 66 patients with glaucoma and 53 patients with cataracts but no glaucoma was carried out. The surface tension of rabbit aqueous humor was 65.9 ± 1.2; vitreous, 60.6 ± 2.6; and balanced salt solution, 70.7 ± 0.9. Timolol and latanoprost did not alter the surface tension of the aqueous humor in the rabbit model. The average surface tension of human aqueous humor was 63.33 ± 4.0 (glaucomatous eyes) and 66.19 ± 2.64 (nonglaucomatous eyes with cataracts) (P=0.0001). A technique of measuring the surface tension from small quantities of aqueous humor is validated. Surface tension of the aqueous humor in glaucoma patients was less than that of cataract patients.


    African Journals Online (AJOL)

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    properties on aerosil and increase the contact angles on the glass slides to extents that depend on the silane used as well as the concentration of residual silanols and that of surface silyl groups. KEY WORDS: KEY WORDS: Modified aerosil, Surface characterisation, Ethanol adsorption, Contact angle. INTRODUCTION.

  5. Sustaining dry surfaces under water

    DEFF Research Database (Denmark)

    Jones, Paul R.; Hao, Xiuqing; Cruz-Chu, Eduardo R.


    not been investigated, and are critically important to maintain surfaces dry under water.In this work, we identify the critical roughness scale, below which it is possible to sustain the vapor phase of water and/or trapped gases in roughness valleys – thus keeping the immersed surface dry. Theoretical...

  6. Sculpturing Surfaces with Cartan Ribbons

    DEFF Research Database (Denmark)

    Raffaelli, Matteo; Bohr, Jakob; Markvorsen, Steen


    Using the concepts of Cartan development and rolling from differential geometry we develop a method for sculpturing any surface with the use of Cartan ribbons.......Using the concepts of Cartan development and rolling from differential geometry we develop a method for sculpturing any surface with the use of Cartan ribbons....

  7. Dilution of Buoyant Surface Plumes

    DEFF Research Database (Denmark)

    Larsen, Torben; Petersen, Ole

    The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls.......The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls....

  8. Boundaries of flat compact surfaces

    DEFF Research Database (Denmark)

    Røgen, Peter


    type. The number of $3$-singular points (points of zero curvature or if not then of zero torsion) on the boundary of a flat immersed compact surface is greater than or equal to twice the absolute value of the Euler characteristic of the surface. A set of necessary and, in a weakened sense, sufficient...

  9. Spanning quadrangulations of triangulated surfaces

    DEFF Research Database (Denmark)

    Kündgen, André; Thomassen, Carsten


    In this paper we study alternating cycles in graphs embedded in a surface. We observe that 4-vertex-colorability of a triangulation on a surface can be expressed in terms of spanninq quadrangulations, and we establish connections between spanning quadrangulations and cycles in the dual graph whic...

  10. Luminescent Surface Quaternized Carbon Dots

    KAUST Repository

    Bourlinos, Athanasios B.


    Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

  11. Covariant Description of Isothermic Surfaces (United States)

    Tafel, J.


    We present a covariant formulation of the Gauss-Weingarten equations and the Gauss-Mainardi-Codazzi equations for surfaces in 3-dimensional curved spaces. We derive a coordinate invariant condition on the first and second fundamental form which is locally necessary and sufficient for the surface to be isothermic. We show how to construct isothermic coordinates.

  12. Modeling for Standoff Surface Detection (United States)


    spectrum of the scattered radiation is characteristic of the contaminant or the surface it impacts. If this latter energy has sufficient intensity and...interest in determining the surface energy of the evaporated aluminum film on EMF Corporation (Ithaca, NY) microscope slides. An average value was

  13. Hyperbolic surfaces in the Grassmannian

    NARCIS (Netherlands)

    Eendebak, P.T.


    In this article we study real 2-dimensional surfaces in the Grassmannian of 2-planes in a 4-dimensional vector space. These surfaces occur naturally as the fibers of jet bundles of partial differential equations. On the Grassmannian there is an invariant conformal quadratic form and we will use the

  14. Surfaces parametrised by the normals

    DEFF Research Database (Denmark)

    Gravesen, Jens


    the origin to the tangent plane and the surface is simply considered as the envelope of its family of tangent planes. Suppose we are given points and normals and we want a C^k-surface interpolating these data. The data gives the value and gradients of the support function at certain points (the given normals...

  15. Scanning Surface Potential Microscopy of Spore Adhesion on Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ida [University of Tennessee, Knoxville (UTK); Chung, Eunhyea [Georgia Institute of Technology; Kweon, Hyojin [Georgia Institute of Technology; Yiacoumi, Sotira [Georgia Institute of Technology; Tsouris, Costas [ORNL


    The adhesion of spores of Bacillus anthracis - the cause of anthrax and a likely biological threat - to solid surfaces is an important consideration in cleanup after an accidental or deliberate release. However, because of safety concerns, directly studying B. anthracis spores with advanced instrumentation is problematic. As a first step, we are examining the electrostatic potential of Bacillus thuringiensis (Bt), which is a closely related species that is often used as a simulant to study B. anthracis. Scanning surface potential microscopy (SSPM), also known as Kelvin probe force microscopy (KPFM), was used to investigate the influence of relative humidity (RH) on the surface electrostatic potential of Bt that had adhered to silica, mica, or gold substrates. AFM/SSPM side-by-side images were obtained separately in air, at various values of RH, after an aqueous droplet with spores was applied on each surface and allowed to dry before measurements. In the SSPM images, a negative potential on the surface of the spores was observed compared with that of the substrates. The surface potential decreased as the humidity increased. Spores were unable to adhere to a surface with an extremely negative potential, such as mica.

  16. Strategic surfaces in sheet metal forming

    DEFF Research Database (Denmark)

    Olsson, David Dam; Andreasen, Jan Lasson; Bay, Niels

    Out-line: Introduction to tribology in sheet metal forming Developed strategic surfaces Tribological testing of strategic surfaces Conclusion......Out-line: Introduction to tribology in sheet metal forming Developed strategic surfaces Tribological testing of strategic surfaces Conclusion...

  17. Surface states in photonic crystals

    Directory of Open Access Journals (Sweden)

    Vojtíšek P.


    Full Text Available Among many unusual and interesting physical properties of photonic crystals (PhC, in recent years, the propagation of surface electromagnetic waves along dielectric PhC boundaries have attracted considerable attention, also in connection to their possible applications. Such surfaces states, produced with the help of specialized defects on PhC boundaries, similarly to surfaces plasmons, are localized surfaces waves and, as such, can be used in various sensing applications. In this contribution, we present our recent studies on numerical modelling of surface states (SS for all three cases of PhC dimensionality. Simulations of these states were carried out by the use of plane wave expansion (PWE method via the MIT MPB package.

  18. Molecular tailoring of solid surfaces

    CERN Document Server

    Evenson, S A


    The overall performance of a material can be dramatically improved by tailoring its surface at the molecular level. The aim of this project was to develop a universal technique for attaching dendrimers (well-defined, nanoscale, functional polymers) and Jeffamines (high molecular weight polymer chains) to the surface of any shaped solid substrate. This desire for controlled functionalization is ultimately driven by the need to improve material compatibility in various biomedical applications. Atomic force microscopy (AFM) was used initially to study the packing and structure of Langmuir-Blodgett films on surfaces, and subsequently resulted in the first visualization of individual, spherically shaped, nanoscopic polyamidoamine dendrimers. The next goal was to develop a methodology for attaching such macromolecules to inert surfaces. Thin copolymer films were deposited onto solid substrates to produce materials with a fixed concentration of surface anhydride groups. Vapor-phase functionalization reactions were t...

  19. Surface electrostatics: theory and computations

    KAUST Repository

    Chatzigeorgiou, G.


    The objective of this work is to study the electrostatic response of materials accounting for boundary surfaces with their own (electrostatic) constitutive behaviour. The electric response of materials with (electrostatic) energetic boundary surfaces (surfaces that possess material properties and constitutive structures different from those of the bulk) is formulated in a consistent manner using a variational framework. The forces and moments that appear due to bulk and surface electric fields are also expressed in a consistent manner. The theory is accompanied by numerical examples on porous materials using the finite-element method, where the influence of the surface electric permittivity on the electric displacement, the polarization stress and the Maxwell stress is examined.

  20. Physics of Surfaces and Interfaces

    CERN Document Server

    Ibach, Harald


    This graduate-level textbook covers the major developments in surface sciences of recent decades, from experimental tricks and basic techniques to the latest experimental methods and theoretical understanding. It is unique in its attempt to treat the physics of surfaces, thin films and interfaces, surface chemistry, thermodynamics, statistical physics and the physics of the solid/electrolyte interface in an integral manner, rather than in separate compartments. The Physics of Surfaces and Interfaces is designed as a handbook for the researcher as well as a study-text for graduate students in physics or chemistry with special interest in the surface sciences, material science, or the nanosciences. The experienced researcher, professional or academic teacher will appreciate the opportunity to share many insights and ideas that have grown out of the author's long experience. Readers will likewise appreciate the wide range of topics treated, each supported by extensive references. Graduate students will benefit f...

  1. Pancake bouncing on superhydrophobic surfaces (United States)

    Liu, Yahua; Moevius, Lisa; Xu, Xinpeng; Qian, Tiezheng; Yeomans, Julia M.; Wang, Zuankai


    Engineering surfaces that promote rapid drop detachment is of importance to a wide range of applications including anti-icing, dropwise condensation and self-cleaning. Here we show how superhydrophobic surfaces patterned with lattices of submillimetre-scale posts decorated with nanotextures can generate a counter-intuitive bouncing regime: drops spread on impact and then leave the surface in a flattened, pancake shape without retracting. This allows a fourfold reduction in contact time compared with conventional complete rebound . We demonstrate that the pancake bouncing results from the rectification of capillary energy stored in the penetrated liquid into upward motion adequate to lift the drop. Moreover, the timescales for lateral drop spreading over the surface and for vertical motion must be comparable. In particular, by designing surfaces with tapered micro/nanotextures that behave as harmonic springs, the timescales become independent of the impact velocity, allowing the occurrence of pancake bouncing and rapid drop detachment over a wide range of impact velocities.

  2. Minimal Surfaces for Hitchin Representations

    DEFF Research Database (Denmark)

    Li, Qiongling; Dai, Song


    . In this paper, we investigate the properties of immersed minimal surfaces inside symmetric space associated to a subloci of Hitchin component: $q_n$ and $q_{n-1}$ case. First, we show that the pullback metric of the minimal surface dominates a constant multiple of the hyperbolic metric in the same conformal...... class and has a strong rigidity property. Secondly, we show that the immersed minimal surface is never tangential to any flat inside the symmetric space. As a direct corollary, the pullback metric of the minimal surface is always strictly negatively curved. In the end, we find a fully decoupled system......Given a reductive representation $\\rho: \\pi_1(S)\\rightarrow G$, there exists a $\\rho$-equivariant harmonic map $f$ from the universal cover of a fixed Riemann surface $\\Sigma$ to the symmetric space $G/K$ associated to $G$. If the Hopf differential of $f$ vanishes, the harmonic map is then minimal...

  3. Capillary waves with surface viscosity (United States)

    Shen, Li; Denner, Fabian; Morgan, Neal; van Wachem, Berend; Dini, Daniele


    Experiments over the last 50 years have suggested a correlation between the surface (shear) viscosity and the stability of a foam or emulsion. With recent techniques allowing more accurate measurements of the elusive surface viscosity, we examine this link theoretically using small-amplitude capillary waves in the presence of the Marangoni effect and surface viscosity modelled via the Boussinesq-Scriven model. The surface viscosity effect is found to contribute a damping effect on the amplitude of the capillary wave with subtle differences to the effect of the convective-diffusive Marangoni transport. The general wave dispersion is augmented to take into account the Marangoni and surface viscosity effects, and a first-order correction to the critical damping wavelength is derived. The authors acknowledge the financial support of the Shell University Technology Centre for fuels and lubricants.

  4. Modern techniques of surface science

    CERN Document Server

    Woodruff, D Phil


    This fully revised, updated and reorganised third edition provides a thorough introduction to the characterisation techniques used in surface science and nanoscience today. Each chapter brings together and compares the different techniques used to address a particular research question, including how to determine the surface composition, surface structure, surface electronic structure, surface microstructure at different length scales (down to sub-molecular), and the molecular character of adsorbates and their adsorption or reaction properties. Readers will easily understand the relative strengths and limitations of the techniques available to them and, ultimately, will be able to select the most suitable techniques for their own particular research purposes. This is an essential resource for researchers and practitioners performing materials analysis, and for senior undergraduate students looking to gain a clear understanding of the underlying principles and applications of the different characterisation tec...

  5. Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vihma, T.


    Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

  6. Upscaling and Downscaling of Land Surface Fluxes with Surface Temperature (United States)

    Kustas, W. P.; Anderson, M. C.; Hain, C.; Albertson, J. D.; Gao, F.; Yang, Y.


    Land surface temperature (LST) is a key surface boundary condition that is significantly correlated to surface flux partitioning between latent and sensible heat. The spatial and temporal variation in LST is driven by radiation, wind, vegetation cover and roughness as well as soil moisture status in the surface and root zone. Data from airborne and satellite-based platforms provide LST from ~10 km to sub meter resolutions. A land surface scheme called the Two-Source Energy Balance (TSEB) model has been incorporated into a multi-scale regional modeling system ALEXI (Atmosphere Land Exchange Inverse) and a disaggregation scheme (DisALEXI) using higher resolution LST. Results with this modeling system indicates that it can be applied over heterogeneous land surfaces and estimate reliable surface fluxes with minimal in situ information. Consequently, this modeling system allows for scaling energy fluxes from subfield to regional scales in regions with little ground data. In addition, the TSEB scheme has been incorporated into a large Eddy Simulation (LES) model for investigating dynamic interactions between variations in the land surface state reflected in the spatial pattern in LST and the lower atmospheric air properties affecting energy exchange. An overview of research results on scaling of fluxes and interactions with the lower atmosphere from the subfield level to regional scales using the TSEB, ALEX/DisALEX and the LES-TSEB approaches will be presented. Some unresolved issues in the use of LST at different spatial resolutions for estimating surface energy balance and upscaling fluxes, particularly evapotranspiration, will be discussed.

  7. Polyspecies biofilm formation on implant surfaces with different surface characteristics

    Directory of Open Access Journals (Sweden)

    Patrick R. SCHMIDLIN


    Full Text Available Objective To investigate the microbial adherence and colonization of a polyspecies biofilm on 7 differently processed titanium surfaces. Material and Methods Six-species biofilms were formed anaerobically on 5-mm-diameter sterilized, saliva-preconditioned titanium discs. Material surfaces used were either machined, stained, acid-etched or sandblasted/acid-etched (SLA. Samples of the latter two materials were also provided in a chemically modified form, with increased wettability characteristics. Surface roughness and contact angles of all materials were determined. The discs were then incubated anaerobically for up to 16.5 h. Initial microbial adherence was evaluated after 20 min incubation and further colonization after 2, 4, 8, and 16.5 h using non-selective and selective culture techniques. Results at different time points were compared using ANOVA and Scheffé post hoc analysis. Results The mean differences in microorganisms colonizing after the first 20 min were in a very narrow range (4.5 to 4.8 log CFU. At up to 16.5 h, the modified SLA surface exhibited the highest values for colonization (6.9±0.2 log CFU, p<0.05 but increasing growth was observed on all test surfaces over time. Discrepancies among bacterial strains on the differently crafted titanium surfaces were very similar to those described for total log CFU. F. nucleatum was below the detection limit on all surfaces after 4 h. Conclusion Within the limitations of this in vitro study, surface roughness had a moderate influence on biofilm formation, while wettability did not seem to influence biofilm formation under the experimental conditions described. The modified SLA surface showed the highest trend for bacterial colonization.

  8. Modification of Surface Energy via Direct Laser Ablative Surface Patterning (United States)

    Wohl, Christopher J., Jr. (Inventor); Belcher, Marcus A. (Inventor); Connell, John W. (Inventor); Hopkins, John W. (Inventor)


    Surface energy of a substrate is changed without the need for any template, mask, or additional coating medium applied to the substrate. At least one beam of energy directly ablates a substrate surface to form a predefined topographical pattern at the surface. Each beam of energy has a width of approximately 25 micrometers and an energy of approximately 1-500 microJoules. Features in the topographical pattern have a width of approximately 1-500 micrometers and a height of approximately 1.4-100 micrometers.

  9. Compressive Surface Stress in Magnetic Transition Metals (United States)

    Punkkinen, M. P. J.; Kwon, S. K.; Kollár, J.; Johansson, B.; Vitos, L.


    Because of the increased electron density within the surface layer, metal surfaces are generally expected to have tensile surface stress. Here, using first-principles density functional calculations, we demonstrate that in magnetic 3d metals surface magnetism can alter this commonly accepted picture. We find that the thermodynamically stable surfaces of chromium and manganese possess compressive surface stress. The revealed negative surface stress is shown to be ascribed to the enhanced magnetic moments within the surface layer relative to the bulk values.

  10. Surface impedance and optimum surface resistance of a superconductor with an imperfect surface (United States)

    Gurevich, Alex; Kubo, Takayuki


    We calculate a low-frequency surface impedance of a dirty, s -wave superconductor with an imperfect surface incorporating either a thin layer with a reduced pairing constant or a thin, proximity-coupled normal layer. Such structures model realistic surfaces of superconducting materials which can contain oxide layers, absorbed impurities, or nonstoichiometric composition. We solved the Usadel equations self-consistently and obtained spatial distributions of the order parameter and the quasiparticle density of states which then were used to calculate a low-frequency surface resistance Rs(T ) and the magnetic penetration depth λ (T ) as functions of temperature in the limit of local London electrodynamics. It is shown that the imperfect surface in a single-band s -wave superconductor results in a nonexponential temperature dependence of Z (T ) at T ≪Tc which can mimic the behavior of multiband or d -wave superconductors. The imperfect surface and the broadening of the gap peaks in the quasiparticle density of states N (ɛ ) in the bulk give rise to a weakly temperature-dependent residual surface resistance. We show that the surface resistance can be optimized and even reduced below its value for an ideal surface by engineering N (ɛ ) at the surface using pair-breaking mechanisms, particularly by incorporating a small density of magnetic impurities or by tuning the thickness and conductivity of the normal layer and its contact resistance. The results of this work address the limit of Rs in superconductors at T ≪Tc , and the ways of engineering the optimal density of states by surface nanostructuring and impurities to reduce losses in superconducting microresonators, thin-film strip lines, and radio-frequency cavities for particle accelerators.

  11. Reconstruction of Kinematic Surfaces from Scattered Data

    DEFF Research Database (Denmark)

    Randrup, Thomas; Pottmann, Helmut; Lee, I.-K.


    Given a surface in 3-space or scattered points from a surface, we present algorithms for fitting the data by a surface which can be generated by a one--parameter subgroup of the group of similarities. These surfaces are general cones and cylinders, surfaces of revolution, helical surfaces and spi...

  12. SMEX02 Land Surface Information: Geolocation, Surface Roughness, and Photographs (United States)

    National Aeronautics and Space Administration — This data set combines various ancillary data (geolocation, surface roughness, and photographs) collected for the Iowa Soil Moisture Experiment 2002 (SMEX02) study...

  13. The Surface Chemical Properties of Novel High Surface Area Solids ...

    African Journals Online (AJOL)

    Spectroscopic and potentiometric investigations into the surface properties of both solids ... solids (unmodified ash, base-modified ash, acid-etched zeolitic product) are reported. Metal sorption studies were performed for cadmium and copper.

  14. Surface metrology by phase contrast (United States)

    Baker, Lionel R.


    Increasing use of electrooptical imaging and detection systems in thermography high density information storage laser instrumentation and X-ray optics has led to a pressing need for machinecompatible sensors for the measurement of surface texture. This paper reviews recent advances in the use of deterministic and parametric noncontact methods for texture measurement and justifies the need for objective simple and yet precise means for displaying the microfinish of a machined surface. The design of a simple two channel phase contrast microscope is described which can be calibrated by test pieces and used as a means for optimising the process parameters involved in the generation of high quality surfaces. Typical results obtained with this technique including dynamic range and ultimate sensitivity are discussed. 1 . NEED FOR SURFACE METROLOGY Surface quality has a direct influence on product acceptability in many different industries including those concerned with optoelectronics and engineering. The influence may be cosmetic as with paint finish on a motor car body or functional for example when excessive wear rates may occur in a bearing surface with inadequate oil retention. Since perfection can never be achieved and overspecification can be costly it is clearly necessary to be able to define thresholds of acceptance in relation to different situations. Such thresholds do of course require agreed methods of measurement with traceability to national standards. The current trends in surface metrology are towards higher

  15. Surface scattering from ceramic phosphors (United States)

    Lenef, Alan; Kelso, John; Peters, Christopher


    Scattering from phosphor converters and epitaxial surfaces is critical for solid state lighting device performance. Volume and surface scattering in solid state lighting devices can play a critical role in efficiency/efficacy, color points, and color angular consistency. Surface scattering in particular has not been well characterized in solid state lighting devices and can be complex to model. Because large angle scattering is important in lighting applications, surface scattering models generally require vector electromagnetic theory to avoid ambiguities often associated with scalar theory at these angles. Furthermore, surface features are often on the order of a few wavelengths, bringing ray tracing approaches into question. In this work, experimental angular scattering measurements are made on ceramic phosphor components where surface scattering dominates. The surface ceramic grain structure is responsible for the scattering. The results are compared to approximate statistical vector theory predictions that use the height autocorrelation functions as input. The autocorrelation measurements were derived from atomic-force microscopy topography measurements. Resulting predictions are in fairly good agreement with measurements.

  16. Surface stress, surface elasticity, and the size effect in surface segregation

    DEFF Research Database (Denmark)

    Schmid, M.; Hofer, W.; Varga, P.


    Surface stress and surface elasticity of low-index fcc surfaces have been studied using effective-medium theory potentials. In addition to total-energy calculations giving stress components and elastic data for the surface as a whole, the use of artificial atoms with modified size allows us...... to probe the stress and elasticity of individual layers. This method of artificial atoms provides a direct way to study the contribution of atomic size to segregation in alloys as well as the driving force of reconstructions driven by surface stress. As an example, we give a qualitative explanation...... of the face-dependent segregation of Pt-Ni alloys. We also compare results of these atomic-scale calculations with continuum elasticity....


    Directory of Open Access Journals (Sweden)

    Şeyda Erşahan


    Full Text Available Purpose: To compare the effects of different methods of surface treatment on enamel roughness. Materials and Methods: Ninety human maxillary first premolars were randomly divided into three groups (n=30 according to type of enamel surface treatment: I, acid etching; II, Er:YAG laser; III, Nd:YAG laser. The surface roughness of enamel was measured with a noncontact optical profilometer. For each enamel sample, two readings were taken across the sample—before enamel surface treatment (T1 and after enamel surface treatment (T2. The roughness parameter analyzed was the average roughness (Ra. Statistical analysis was performed using a Paired sample t test and the post-hoc Mann- Whitney U test, with the significance level set at 0.05. Results: The highest Ra (average roughness values were observed for Group II, with a significant difference with Groups I and III (P<0.001. Ra values for the acid etching group (Group I were significantly lower than other groups (P<0.001. Conclusion: Surface treatment of enamel with Er:YAG laser and Nd:YAG laser results in significantly higher Ra than acid-etching. Both Er:YAG laser or Nd:YAG laser can be recommended as viable treatment alternatives to acid etching.

  18. Surface Wrinkling on Polydimethylsiloxane Microspheres via Wet Surface Chemical Oxidation (United States)

    Yin, Jian; Han, Xue; Cao, Yanping; Lu, Conghua


    Here we introduce a simple low-cost yet robust method to realize spontaneously wrinkled morphologies on spherical surfaces. It is based on surface chemical oxidation of aqueous-phase-synthesized polydimethylsiloxane (PDMS) microspheres in the mixed H2SO4/HNO3/H2O solution. Consequently, curvature and overstress-sensitive wrinkles including dimples and labyrinth patterns are successfully induced on the resulting oxidized PDMS microspheres. A power-law dependence of the wrinkling wavelength on the microsphere radius exists. The effects of experimental parameters on these tunable spherical wrinkles have been systematically investigated, when the microspheres are pre-deposited on a substrate. These parameters include the radius and modulus of microspheres, the mixed acid solution composition, the oxidation duration, and the water washing post-treatment. Meanwhile, the complicated chemical oxidation process has also been well studied by in-situ optical observation via the microsphere system, which represents an intractable issue in a planar system. Furthermore, we realize surface wrinkled topographies on the whole microspheres at a large scale, when microspheres are directly dispersed in the mixed acid solution for surface oxidation. These results indicate that the introduced wet surface chemical oxidation has the great potential to apply to other complicated curved surfaces for large-scale generation of well-defined wrinkling patterns, which endow the solids with desired physical properties.

  19. Plastic Deformation of Metal Surfaces

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu


    parameters by TEM and EBSD and apply strength-structural relationships established for the bulk metal deformed to high strains. This technique has been applied to steel deformed by high energy shot peening and a calculated stress gradient at or near the surface has been successfully validated by hardness......Plastic deformation of metal surfaces by sliding and abrasion between moving parts can be detrimental. However, when the plastic deformation is controlled for example by applying different peening techniques hard surfaces can be produced which can increase the fracture resistance and fatigue life...

  20. Flexible Multiplexed Surface Temperature Sensor (United States)

    Daryabeigi, Kamran; Dillon-Townes, L. A.; Johnson, Preston B.; Ash, Robert L.


    Unitary array of sensors measures temperatures at points distributed over designated area on surface. Useful in measuring surface temperatures of aerodynamic models and thermally controlled objects. Made of combination of integrated-circuit microchips and film circuitry. Temperature-sensing chips scanned at speeds approaching 10 kHz. Operating range minus 40 degrees C to 120 degrees C. Flexibility of array conforms to curved surfaces. Multiplexer eliminates numerous monitoring cables. Control of acquisition and recording of data effected by connecting array to microcomputers via suitable interface circuitry.


    Directory of Open Access Journals (Sweden)


    Full Text Available The article deals with known cases of operation of seaplanes and amphibians in the snow-covered surfaces. On the basis of the existing data on the resistance and acceleration acting on the hull of planing snowplane analysis of possible acting on the bottom of the amphibious aircraft weighing 37 tons moving in the snow-covered surface was carried out. Estimates have shown the possibility of the takeoff of such plane while moving in the snow-covered surface. Vertical acceleration and landing hit will not exceed the maximum permissible value if the thickness of the snow cover is not less than 1 meter.

  2. Surface wrinkling on polydopamine film (United States)

    Meng, Jieyun; Xie, Jixun; Han, Xue; Lu, Conghua


    In this paper, we report a non-lithographic strategy to realize surface patterns on polydopamine films. It is based on surface wrinkling, which is induced on polydopamine (PDA) films that are grown on uniaxially pre-strained polydimethylsiloxane (PDMS) substrates through self-polymerization of dopamine, followed by the pre-strain release. We investigate the influences of the experimental conditions including polymerization time, prestrain and the dopamine solution concentration on the wrinkling patterns. Furthermore, we take advantage of the reducibility of PDA to fabricate silver nanoparticle-deposited PDA films with surface-wrinkled patterns, which may have potential applications in the related fields.

  3. Optical Isolator Utilizing Surface Plasmons

    Directory of Open Access Journals (Sweden)

    Shinji Yuasa


    Full Text Available Feasibility of usage of surface plasmons in a new design of an integrated optical isolator has been studied. In the case of surface plasmons propagating at a boundary between a transition metal and a double-layer dielectric, there is a significant difference of optical loss for surface plasmons propagating in opposite directions. Utilizing this structure, it is feasible to fabricate a competitive plasmonic isolator, which benefits from a broad wavelength operational bandwidth and a good technological compatibility for integration into the Photonic Integrated Circuits (PIC. The linear dispersion relation was derived for plasmons propagating in a multilayer magneto-optical slab.

  4. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    related to inaccurate land surface modelling, e.g. enhanced warm bias in warm dry summer months. Coupling the regional climate model to a hydrological model shows the potential of improving the surface flux simulations in dry periods and the 2 m air temperature in general. In the dry periods......The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  5. Nanobubble trouble on gold surfaces

    DEFF Research Database (Denmark)

    Holmberg, Maria; Kuhle, A.; Garnaes, J.


    When analyzing surfaces related to biosensors with in situ atomic force microscopy (AFM), the existence of nanobubbles called for our attention. The bubbles seem to form spontaneously when gold surfaces are immersed in clean water and are probably a general phenomenon at water-solid interfaces....... Besides from giving rise to undesired effects in, for example, biosensors, nanobubbles can also cause artifacts in AFM imaging. We have observed nanobubbles on unmodified gold surfaces, immersed in clean water, using standard silicon AFM probes. Nanobubbles can be made to disappear from contact mode AFM...

  6. Subdivision depth for triangular surfaces

    Directory of Open Access Journals (Sweden)

    G. Mustafa


    Full Text Available The aim of this attempt was to present an efficient algorithm for the evaluation of error bound of triangular subdivision surfaces. The error estimation technique is based on first order difference and this process is independent of parametrization. This technique can be easily generalized to higher arity triangular surfaces. The estimated error bound is expressed in-terms of initial control point sequence and constants. Here, we efficiently estimate error bound between triangular surface and its control polygon after k-fold subdivision and further extended to evaluate subdivision depth of the scheme.

  7. Pancake bouncing on superhydrophobic surfaces


    Liu, Yahua; Moevius, Lisa; Xu, Xinpeng; Qian, Tiezheng; Yeomans, Julia M.; Wang, Zuankai


    Engineering surfaces that promote rapid drop detachment1,2 is of importance to a wide range of applications including anti-icing3?5, dropwise condensation6, and self-cleaning7?9. Here we show how superhydrophobic surfaces patterned with lattices of submillimetre-scale posts decorated with nano-textures can generate a counter-intuitive bouncing regime: drops spread on impact and then leave the surface in a flattened, pancake shape without retracting. This allows for a four-fold reduction in co...

  8. Surface Modification and Surface - Subsurface Exchange Processes on Europa (United States)

    Phillips, Cynthia B.; Molaro, Jamie; Hand, Kevin P.


    The surface of Jupiter’s moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa’s leading-trailing hemisphere brightness asymmetry.Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted “chaos-type” terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features.In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa’s surface area.Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age (~50myr) of Europa. Quantifying the

  9. ISLSCP II Sea Surface Temperature (United States)

    National Aeronautics and Space Administration — Sea surface temperature (SST) is an important indicator of the state of the earth climate system as well as a key variable in the coupling between the atmosphere and...

  10. Gap Surface Plasmon Waveguide Analysis

    DEFF Research Database (Denmark)

    Nielsen, Michael Grøndahl; Bozhevolnyi, Sergey I.


    Plasmonic waveguides supporting gap surface plasmons (GSPs) localized in a dielectric spacer between metal films are investigated numerically and the waveguiding properties at telecommunication wavelengths are presented. Especially, we emphasize that the mode confinement can advantageously be con...

  11. Surface Tension and Capillary Rise (United States)

    Walton, Alan J.


    Discussion of the shortcomings of textbook explanations of surface tension, distinguishing between concepts of tension and capillary rise. The arguments require only a clear understanding of Newtonian mechanics, notably potential energy. (DF)

  12. Surface Modification for Microreactor Fabrication

    Directory of Open Access Journals (Sweden)

    Wladyslaw Torbicz


    Full Text Available In this paper, methods of surface modification of different supports, i.e. glass andpolymeric beads for enzyme immobilisation are described. The developed method ofenzyme immobilisation is based on Schiff’s base formation between the amino groups onthe enzyme surface and the aldehyde groups on the chemically modified surface of thesupports. The surface of silicon modified by APTS and GOPS with immobilised enzymewas characterised by atomic force microscopy (AFM, time-of-flight secondary ion massspectroscopy (ToF-SIMS and infrared spectroscopy (FTIR. The supports withimmobilised enzyme (urease were also tested in combination with microreactors fabricatedin silicon and Perspex, operating in a flow-through system. For microreactors filled withurease immobilised on glass beads (Sigma and on polymeric beads (PAN, a very high andstable signal (pH change was obtained. The developed method of urease immobilisationcan be stated to be very effective.

  13. BLM Colorado Surface Management Agency (United States)

    Department of the Interior — Shapefile Format – Illustratation of the surface management agency for lands within the state of Colorado. Formerly called land status. This data set is a result of...

  14. Surface-Enhanced Raman Spectroscopy

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 2. Surface-Enhanced Raman Spectroscopy - Recent Advancement of Raman Spectroscopy. Ujjal Kumar Sur. General Article Volume 15 Issue 2 February 2010 pp 154-164 ...

  15. Total Phosphorus in Surface Water (United States)

    U.S. Environmental Protection Agency — Excess phosphorus in surface water can result in eutrophication. TOTALP is reported in kilograms/hectare/year. More information about these resources, including the...

  16. Total Nitrogen in Surface Water (United States)

    U.S. Environmental Protection Agency — Excess nitrogen in surface water can result in eutrophication. TOTALN is reported in kilograms/hectare/year. More information about these resources, including the...

  17. ISLSCP II Sea Surface Temperature (United States)

    National Aeronautics and Space Administration — ABSTRACT: Sea surface temperature (SST) is an important indicator of the state of the earth climate system as well as a key variable in the coupling between the...

  18. Free Surface Water Tunnel (FSWT) (United States)

    Federal Laboratory Consortium — Description: The Free Surface Water Tunnel consists of the intake plenum, the test section and the exit plenum. The intake plenum starts with a perforated pipe that...

  19. Surface Meteorology and Solar Energy (United States)

    National Aeronautics and Space Administration — Surface Meteorology and Solar Energy data - over 200 satellite-derived meteorology and solar energy parameters, monthly averaged from 22 years of data, global solar...

  20. Silicosis in surface coalmine drillers. (United States)

    Banks, D E; Bauer, M A; Castellan, R M; Lapp, N L


    Surface coalminers are generally thought to be at minimal risk of developing pneumoconiosis. Biopsy-proved silicoproteinosis was found in a 34-year-old surface coalmine driller, and two of nine other drill crew members who worked for the same company had chest radiographic findings compatible with simple silicosis. Reanalysis of data from a previous United States Public Health Service survey of surface coalminers, after exclusion of those with underground mining experience, showed that 38% of the cases of pneumoconiosis occurred in drill crew members, a group comprising only 11% of the study population. On the basis of these data surface coalmine drillers appear to have an increased risk of developing occupational lung disease.

  1. Machining of Complex Sculptured Surfaces

    CERN Document Server


    The machining of complex sculptured surfaces is a global technological topic in modern manufacturing with relevance in both industrialized and emerging in countries particularly within the moulds and dies sector whose applications include highly technological industries such as the automotive and aircraft industry. Machining of Complex Sculptured Surfaces considers new approaches to the manufacture of moulds and dies within these industries. The traditional technology employed in the manufacture of moulds and dies combined conventional milling and electro-discharge machining (EDM) but this has been replaced with  high-speed milling (HSM) which has been applied in roughing, semi-finishing and finishing of moulds and dies with great success. Machining of Complex Sculptured Surfaces provides recent information on machining of complex sculptured surfaces including modern CAM systems and process planning for three and five axis machining as well as explanations of the advantages of HSM over traditional methods ra...

  2. OW CCMP Ocean Surface Wind (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Cross-Calibrated Multi-Platform (CCMP) Ocean Surface Wind Vector Analyses (Atlas et al., 2011) provide a consistent, gap-free long-term time-series of monthly...


    African Journals Online (AJOL)

    KEY WORDS: Supramolecular architecture, Hirschfeld surface analysis, Magnetism. INTRODUCTION. Coordination polymers (CPs) have attracted intense attention in recent years ... The hydrogen atoms of organic ligands were placed in calculated positions and refined using a riding on attached atoms with isotropic.

  4. The spectrum of hyperbolic surfaces

    CERN Document Server

    Bergeron, Nicolas


    This text is an introduction to the spectral theory of the Laplacian on compact or finite area hyperbolic surfaces. For some of these surfaces, called “arithmetic hyperbolic surfaces”, the eigenfunctions are of arithmetic nature, and one may use analytic tools as well as powerful methods in number theory to study them. After an introduction to the hyperbolic geometry of surfaces, with a special emphasis on those of arithmetic type, and then an introduction to spectral analytic methods on the Laplace operator on these surfaces, the author develops the analogy between geometry (closed geodesics) and arithmetic (prime numbers) in proving the Selberg trace formula. Along with important number theoretic applications, the author exhibits applications of these tools to the spectral statistics of the Laplacian and the quantum unique ergodicity property. The latter refers to the arithmetic quantum unique ergodicity theorem, recently proved by Elon Lindenstrauss. The fruit of several graduate level courses at Orsay...

  5. Mirador - Earth Surface and Interior (United States)

    National Aeronautics and Space Administration — Earth Science data access made simple. The goal of the Earth Surface and Interior focus area is to assess, mitigate and forecast the natural hazards that affect...

  6. Thin film surface reconstruction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Imperatori, P. [CNR, Monterotondo Stazione, Rome (Italy). Istituto di Chimica dei materiali


    The study of the atomic structure of surfaces and interfaces is a fundamental step in the knowledge and the development of new materials. Among the several surface-sensitive techniques employed to characterise the atomic arrangements, grazing incidence x-ray diffraction (GIXD) is one of the most powerful. With a simple data treatment, based on the kinematical theory, and using the classical methods of x-ray bulk structure determination, it gives the atomic positions of atoms at a surface or an interface and the atomic displacements of subsurface layers for a complete determination of the structure. In this paper the main features of the technique will be briefly reviewed and selected of application to semiconductor and metal surfaces will be discussed.

  7. High-Luminance Road Surfaces, (United States)


    condition was changed with the decreased use of snow chains and increasing use of studded tires. The studded tires wear down the road surface in a...region, white anorthosite of a uniform and unweathered type is usable as an additive to asphalt con- crete and wear surfacing for asphalt gravel...CLASSIFICATION Of THIS PAGE(W/em Daateoo 20. Abstract (cont’d) resistance to weathering, and the degree of luminosity. Quartzites have the best wear

  8. Corrosion-resistant metal surfaces (United States)

    Sugama, Toshifumi [Wading River, NY


    The present invention relates to metal surfaces having thereon an ultrathin (e.g., less than ten nanometer thickness) corrosion-resistant film, thereby rendering the metal surfaces corrosion-resistant. The corrosion-resistant film includes an at least partially crosslinked amido-functionalized silanol component in combination with rare-earth metal oxide nanoparticles. The invention also relates to methods for producing such corrosion-resistant films.

  9. Computing Visible-Surface Representations, (United States)


    of applications. @ Massachusetts Institute of Technology 1985 "’ki report dcs;crihrs rccarch done at the Arificial lInelligence lhaboratory of the...411FO111 OIMMI bm tpal) IS. SUPPLEMENTARY MOTES None A IS~~~1. KEY WORS (Co~me 01 reerseea ............ MIngUfy ySek It Vision Variational principles...perception of visible surfaces. The explicit representation of visible surfaces, an intermediate goal of computational vision , has since attracted

  10. Active motion on curved surfaces


    Castro-Villarreal, Pavel; Sevilla, Francisco J.


    A theoretical analysis of active motion on curved surfaces is presented in terms of a generalization of the Telegrapher's equation. Such generalized equation is explicitly derived as the polar approximation of the hierarchy of equations obtained from the corresponding Fokker-Planck equation of active particles diffusing on curved surfaces. The general solution to the generalized telegrapher's equation is given for a pulse with vanishing current as initial data. Expressions for the probability...

  11. Atom-specific surface magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Sirotti, F.; Panaccione, G. [Laboratoire pour l`Utilisation du Rayonnement Electromagnetique, Centre National de la Recherche Scientifique, Commissariat a l`Energie Atomique, MESR, F-91405 Orsay (France); Rossi, G. [Laboratorium fuer Festkoerperphysik, Eidgenossische Technische Hochschule-Zuerich, Zuerich CH-8093 (Switzerland)


    A powerful atom-specific surface magnetometry can be based on efficient measurements of magnetic dichroism in {ital l}{gt}0 core level photoemission. The temperature dependence M({ital T}) of the Fe(100) surface magnetization was obtained from the photoemission magnetic asymmetry of 3{ital p} core levels, providing the measure of the surface exchange coupling via the spin-wave stiffness and of the surface critical exponent. Beyond the magnetic order {l_angle}M{r_angle} the photoemission dichroism allows us to derive the energy splitting of the magnetic sublevels of the photoexcited core hole. Fe 3{ital p} photoemission dichroism probes directly the magnetic moment changes of iron atoms at Fe(100) surfaces as a function of structural disorder or sulfur segregation. The appearance of dichroism in the 2{ital p} photoemission of segregated sulfur atoms in the {ital c}(2{times}2)S/Fe(100) superstructure measures the magnetic-moment transfer and shows the possibility of investigating surface magnetochemistry in a very direct way.

  12. The chemical physics of surfaces

    CERN Document Server

    Morrison, Stanley Roy


    Even more importantly, some authors who have contributed substantially to an area may have been overlooked. For this I apologize. I have, however, not attempted to trace techniques or observa­ tions historically, so there is no implication (unless specified) that the authors referred to were or were not the originators of a given method or observation. I would like to acknowledge discussions with co-workers at SFU for input relative to their specialties, to acknowledge the help of students who have pointed out errors and difficulties in the earlier presentation, and to acknowledge the infinite patience of my wife Phyllis while I spent my sabbatical and more in libraries and punching computers. S. Roy Morrison 0 1 Contents Notation XV 1. Introduction 1 1. 1. Surface States and Surface Sites . 1 1. 1. 1. The Chemical versus Electronic Representation of the Surface. 1 1. 1. 2. The Surface State on the Band Diagram 4 1. 1. 3. The Fermi Energy in the Surface State Model. 6 1. 1. 4. Need for Both Surface...

  13. Stretch-minimising stream surfaces

    KAUST Repository

    Barton, Michael


    We study the problem of finding stretch-minimising stream surfaces in a divergence-free vector field. These surfaces are generated by motions of seed curves that propagate through the field in a stretch minimising manner, i.e., they move without stretching or shrinking, preserving the length of their arbitrary arc. In general fields, such curves may not exist. How-ever, the divergence-free constraint gives rise to these \\'stretch-free\\' curves that are locally arc-length preserving when infinitesimally propagated. Several families of stretch-free curves are identified and used as initial guesses for stream surface generation. These surfaces are subsequently globally optimised to obtain the best stretch-minimising stream surfaces in a given divergence-free vector field. Our algorithm was tested on benchmark datasets, proving its applicability to incompressible fluid flow simulations, where our stretch-minimising stream surfaces realistically reflect the flow of a flexible univariate object. © 2015 Elsevier Inc. All rights reserved.

  14. Radioactive Ions for Surface Characterization

    CERN Multimedia


    The collaboration has completed a set of pilot experiments with the aim to develop techniques for using radioactive nuclei in surface physics. The first result was a method for thermal deposition of isolated atoms (Cd, In, Rb) on clean metallic surfaces. \\\\ \\\\ Then the diffusion history of deposited Cd and In atoms on two model surfaces, Mo(110) and Pd(111), was followed through the electric field gradients (efg) acting at the probe nuclei as measured with the Perturbed Angular Correlation technique. For Mo(110) a rather simple history of the adatoms was inferred from the experiments: Atoms initially landing at terrace sites diffuse from there to ledges and then to kinks, defects always present at real surfaces. The next stage is desorption from the surface. For Pd a scenario that goes still further was found. Following the kink stage the adatoms get incorporated into ledges and finally into the top surface layer. For all these five sites the efg's could be measured.\\\\ \\\\ In preparation for a further series o...

  15. Mineralogy of the Mercurian Surface (United States)

    Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Nittler, Larry R.; Peplowski, Patrick N.; Weider, Shoshana Z.; Evans, Larry R.; Frank, Elizabeth A.; McCoy, Timothy


    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited Mercury for four years until April 2015, revealing its structure, chemical makeup, and compositional diversity. Data from the mission have confirmed that Mercury is a compositional end-member among the terrestrial planets. The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) on board MESSENGER provided the first detailed geochemical analyses of Mercury's surface. These instruments have been used in conjunction with the Neutron Spectrometer and the Mercury Dual Imaging System to classify numerous geological and geochemical features on the surface of Mercury that were previously unknown. Furthermore, the data have revealed several surprising characteristics about Mercury's surface, including elevated S abundances (up to 4 wt%) and low Fe abundances (less than 2.5 wt%). The S and Fe abundances were used to quantify Mercury's highly reduced state, i.e., between 2.6 and 7.3 log10 units below the Iron-Wustite (IW) buffer. This fO2 is lower than any of the other terrestrial planets in the inner Solar System and has important consequences for the thermal and magmatic evolution of Mercury, its surface mineralogy and geochemistry, and the petrogenesis of the planet's magmas. Although MESSENGER has revealed substantial geochemical diversity across the surface of Mercury, until now, there have been only limited efforts to understand the mineralogical and petrological diversity of the planet. Here we present a systematic and comprehensive study of the potential mineralogical and petrological diversity of Mercury.

  16. Polymers at Surfaces and Interfaces (United States)

    Tsige, Mesfin


    Interfaces between solids, liquids, and gases play an important role in a wide range of practical applications and have been a subject of scientific interest since Poisson showed in 1831 that the order parameter of liquids near interfaces must deviate considerably from its bulk value. In particular, polymers at surfaces and interfaces have been a subject of extensive theoretical, experimental and computational studies for a long time due to their use in many diverse applications ranging from antifouling coatings to flexible electronic devices. Understanding the structure and thermodynamic properties of polymers at surfaces and interfaces is thus an area of fundamental and current technological interest. Although encouraging experimental progress has been made over the years in understanding the molecular structure of polymers in contact with various environments, selectively probing their structure and dynamics at surfaces and interfaces has been extremely difficult. Computer simulations, especially molecular dynamics (MD) simulations, have proven over the years to be an invaluable tool in providing molecular details at interfaces that are usually lacking in the experimental data. In this talk, I'll give an overview of some previous simulation efforts to understand the structure and dynamics of polymers at surfaces and buried interfaces. I will conclude by presenting our current and ongoing work on combining ab initio calculations and MD simulations with Sum Frequency Generation (SFG) Spectroscopy to study polymer surfaces. This approach demonstrates the future role of MD in surface science. Work supported by NSF (DMR0847580 and DMR1410290) and Petroleum Research Fund of the American Chemical Society.

  17. Parallel Surfaces of Spacelike Ruled Weingarten Surfaces in Minkowski 3-space

    Directory of Open Access Journals (Sweden)

    Yasin Ünlütürk


    Full Text Available In this work, it is shown that parallel surfaces of spacelike ruled surfaces which are developable are spacelike ruled Weingarten surfaces. It is also shown that parallel surfaces of non-developable ruled Weingarten surfaces are again Weingarten surfaces. Finally, some properties of that kind parallel surfaces are obtained in Minkowski 3-space.

  18. Eddy Current Probe for Surface and Sub-Surface Inspection (United States)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)


    An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required.

  19. Ultrafast imaging of surface plasmons propagating on a gold surface. (United States)

    Gong, Yu; Joly, Alan G; Hu, Dehong; El-Khoury, Patrick Z; Hess, Wayne P


    We record time-resolved nonlinear photoemission electron microscopy (tr-PEEM) images of propagating surface plasmons (PSPs) launched from a lithographically patterned rectangular trench on a flat gold surface. Our tr-PEEM scheme involves a pair of identical, spatially separated, and interferometrically locked femtosecond laser pulses. Power-dependent PEEM images provide experimental evidence for a sequential coherent nonlinear photoemission process, in which one laser source launches a PSP through a linear interaction, and the second subsequently probes the PSP via two-photon photoemission. The recorded time-resolved movies of a PSP allow us to directly measure various properties of the surface-bound wave packet, including its carrier wavelength (783 nm) and group velocity (0.95c). In addition, tr-PEEM images reveal that the launched PSP may be detected at least 250 μm away from the coupling trench structure.

  20. Applications of surface analysis and surface theory in tribology (United States)

    Ferrante, John


    Tribology, the study of adhesion, friction and wear of materials, is a complex field which requires a knowledge of solid state physics, surface physics, chemistry, material science, and mechanical engineering. It has been dominated, however, by the more practical need to make equipment work. With the advent of surface analysis and advances in surface and solid-state theory, a new dimension has been added to the analysis of interactions at tribological interfaces. In this paper the applications of tribological studies and their limitations are presented. Examples from research at the NASA Lewis Research Center are given. Emphasis is on fundamental studies involving the effects of monolayer coverage and thick films on friction and wear. A summary of the current status of theoretical calculations of defect energetics is presented. In addition, some new theoretical techniques which enable simplified quantitative calculations of adhesion, fracture, and friction are discussed.

  1. Artefacts for optical surface measurement (United States)

    Robson, Stuart; Beraldin, J.-Angelo; Brownhill, Andrew; MacDonald, Lindsay


    Flexible manufacturing technologies are supporting the routine production of components with freeform surfaces in a wide variety of materials and surface finishes. Such surfaces may be exploited for both aesthetic and performance criteria for a wide range of industries, for example automotive, aircraft, small consumer goods and medial components. In order to ensure conformance between manufactured part and digital design it is necessary to understand, validate and promote best practice of the available measurement technologies. Similar, but currently less quantifiable, measurement requirements also exist in heritage, museum and fine art recording where objects can be individually hand crafted to extremely fine levels of detail. Optical 3D measurement systems designed for close range applications are typified by one or more illumination sources projecting a spot, line or structured light pattern onto a surface or surfaces of interest. Reflections from the projected light are detected in one or more imaging devices and measurements made concerning the location, intensity and optionally colour of the image. Coordinates of locations on the surface may be computed either directly from an understanding of the illumination and imaging geometry or indirectly through analysis of the spatial frequencies of the projected pattern. Regardless of sensing configuration some independent means is necessary to ensure that measurement capability will meet the requirements of a given level of object recording and is consistent for variations in surface properties and structure. As technologies mature, guidelines for best practice are emerging, most prominent at the current time being the German VDI/VDE 2634 and ISO/DIS 10360-8 guidelines. This considers state of the art capabilities for independent validation of optical non-contact measurement systems suited to the close range measurement of table top sized manufactured or crafted objects.

  2. Surface Tension and Adsorption without a Dividing Surface. (United States)

    Marmur, Abraham


    The ingenious concept of a dividing surface of zero thickness that was introduced by Gibbs is the basis of the theory of surface tension and adsorption. However, some fundamental questions, mainly those related to the location of the dividing surface and the proper definition of relative adsorption, have remained open over the years. To avoid these questions, the present paper proposes to analyze an interfacial phase by defining a thermodynamic system of constant, but nonzero thickness. The interfacial phase is analyzed as it really is, namely a nonuniform three-dimensional entity. The current analysis redevelops the equation for calculating surface tension, though with different assumptions. However, the main point in the proposed model is that the thermodynamic interfacial system, due to its fixed thickness, conforms to the requirement of first-order homogeneity of the internal energy. This property is the key that allows using the Gibbs adsorption isotherm. It is also characteristic of the Gibbs dividing surface model, but has not always been discussed with regard to subsequent models. The resulting equation leads to a simple, "natural" expression for the relative adsorption. This expression may be compared with simulations and sophisticated surface concentration measurements, and from which the dependence of interfacial tension on the solution composition can be derived. Finally, it is important to point out that in order to calculate the interfacial tension as well as the relative adsorption from data on the properties of the interfacial phase, there is no need to know its exact thickness, as long as it is bigger than the actual thickness but sufficiently small.

  3. Scattered surface charge density: A tool for surface characterization

    KAUST Repository

    Naydenov, Borislav


    We demonstrate the use of nonlocal scanning tunneling spectroscopic measurements to characterize the local structure of adspecies in their states where they are significantly less perturbed by the probe, which is accomplished by mapping the amplitude and phase of the scattered surface charge density. As an example, we study single-H-atom adsorption on the n-type Si(100)-(4 × 2) surface, and demonstrate the existence of two different configurations that are distinguishable using the nonlocal approach and successfully corroborated by density functional theory. © 2011 American Physical Society.

  4. Liquid Water may Stick on Hydrophobic Surfaces

    Indian Academy of Sciences (India)

    IAS Admin

    The behavior of fluid on a solid surface under static and dynamic conditions are usually clubbed together. • On a wetting surface (hydrophilic), liquid water is believed to adhere to the surface causing multilayer sticking. • On a non-wetting surface (hydrophobic), water is believed to glide across the surface leading to slip ...

  5. Dynamical Modeling of Surface Tension (United States)

    Brackbill, Jeremiah U.; Kothe, Douglas B.


    In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.

  6. Surface-directed spinodal decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Puri, Sanjay [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)


    We review analytical and numerical results for surface-directed spinodal decomposition (SDSD), namely, the interplay of wetting kinetics and phase separation in a binary (AB) mixture in contact with a surface S which prefers one of the components (say, A). Depending on the relative strengths of the A-B, A-S and B-S interactions, the surface is either partially wetted or completely wetted by A in equilibrium. We discuss the theoretical framework for modelling SDSD, and review results obtained from both microscopic and coarse-grained models. We clarify the differences between diffusion-driven SDSD in solids, and SDSD in fluids, where velocity fields play an important role. Furthermore, we discuss the dependence of wetting-layer kinetics on the composition of the mixture. Some results are also presented for phase separation in a confined geometry, e.g., thin films. Finally, we discuss the problem of surface-enrichment kinetics, namely, the kinetics of enrichment of an attracting surface when the bulk mixture is stable. These nonequilibrium processes have important applications in the preparation of nanomaterials and multi-layered structures. (topical review)

  7. Kansei, surfaces and perception engineering (United States)

    Rosen, B.-G.; Eriksson, L.; Bergman, M.


    The aesthetic and pleasing properties of a product are important and add significantly to the meaning and relevance of a product. Customer sensation and perception are largely about psychological factors. There has been a strong industrial and academic need and interest for methods and tools to quantify and link product properties to the human response but a lack of studies of the impact of surfaces. In this study, affective surface engineering is used to illustrate and model the link between customer expectations and perception to controllable product surface properties. The results highlight the use of the soft metrology concept for linking physical and human factors contributing to the perception of products. Examples of surface applications of the Kansei methodology are presented from sauna bath, health care, architectural and hygiene tissue application areas to illustrate, discuss and confirm the strength of the methodology. In the conclusions of the study, future research in soft metrology is proposed to allow understanding and modelling of product perception and sensations in combination with a development of the Kansei surface engineering methodology and software tools.

  8. Pancake bouncing on superhydrophobic surfaces. (United States)

    Liu, Yahua; Moevius, Lisa; Xu, Xinpeng; Qian, Tiezheng; Yeomans, Julia M; Wang, Zuankai


    Engineering surfaces that promote rapid drop detachment1,2 is of importance to a wide range of applications including anti-icing3-5, dropwise condensation6, and self-cleaning7-9. Here we show how superhydrophobic surfaces patterned with lattices of submillimetre-scale posts decorated with nano-textures can generate a counter-intuitive bouncing regime: drops spread on impact and then leave the surface in a flattened, pancake shape without retracting. This allows for a four-fold reduction in contact time compared to conventional complete rebound1,10-13. We demonstrate that the pancake bouncing results from the rectification of capillary energy stored in the penetrated liquid into upward motion adequate to lift the drop. Moreover, the timescales for lateral drop spreading over the surface and for vertical motion must be comparable. In particular, by designing surfaces with tapered micro/nanotextures which behave as harmonic springs, the timescales become independent of the impact velocity, allowing the occurrence of pancake bouncing and rapid drop detachment over a wide range of impact velocities.

  9. Optical Characterization of Nanostructured Surfaces

    DEFF Research Database (Denmark)

    Feidenhans'l, Nikolaj Agentoft

    Micro- and nanostructured surfaces are interesting due to the unique properties they add to the bulk material. One example is structural colors, where the interaction between surface structures and visible light produce bright color effects without the use of paints or dyes. Several research grou...... instrument, and a small study of the implications if the sample surface is covered with an interface layer, e.g. a thin liquid film. For roughness evaluation on hard-to-reach surfaces, the thesis includes a study of surface replication using the thermosetting polymer PDMS....... are investigating the manufacturing of these structures using established high-volume polymer fabrication methods, such as injection molding and roll-to-roll manufacturing. These methods are interesting as they can ease the industrial uptake of nanopatterning technology. However, for a successful industrial...... regions can be analyzed independently. With color scatterometry, a single exposure with the camera is sufficient to evaluate the grating profile for thousands of individual regions spanning a millimeter-sized area. The accuracy of color scatterometry is evaluated on injection molded polymer line gratings...

  10. Surface Passivation of Germanium Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C.; /SLAC, SSRL


    The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed readily by aqueous HF treatment which putatively leaves the nanowire surface hydrogen terminated with limited stability in air. Alternatively, chlorine termination could be achieved by aq. HCl treatment of the native oxide-coated nanowires. Chlorine termination was found to be relatively more stable than the HF-last hydrogen termination.

  11. Spanning quadrangulations of triangulated surfaces

    DEFF Research Database (Denmark)

    Kündgen, André; Thomassen, Carsten


    In this paper we study alternating cycles in graphs embedded in a surface. We observe that 4-vertex-colorability of a triangulation on a surface can be expressed in terms of spanninq quadrangulations, and we establish connections between spanning quadrangulations and cycles in the dual graph which...... are noncontractible and alternating with respect to a perfect matching. We show that the dual graph of an Eulerian triangulation of an orientable surface other than the sphere has a perfect matching M and an M-alternating noncontractible cycle. As a consequence, every Eulerian triangulation of the torus has...... a nonbipartite spanning quadrangulation. For an Eulerian triangulation G of the projective plane the situation is different: If the dual graph G∗ is nonbipartite, then G∗ has no noncontractible alternating cycle, and all spanning quadrangulations of G are bipartite. If the dual graph G∗ is bipartite, then it has...

  12. Surface stress-based biosensors. (United States)

    Sang, Shengbo; Zhao, Yuan; Zhang, Wendong; Li, Pengwei; Hu, Jie; Li, Gang


    Surface stress-based biosensors, as one kind of label-free biosensors, have attracted lots of attention in the process of information gathering and measurement for the biological, chemical and medical application with the development of technology and society. This kind of biosensors offers many advantages such as short response time (less than milliseconds) and a typical sensitivity at nanogram, picoliter, femtojoule and attomolar level. Furthermore, it simplifies sample preparation and testing procedures. In this work, progress made towards the use of surface stress-based biosensors for achieving better performance is critically reviewed, including our recent achievement, the optimally circular membrane-based biosensors and biosensor array. The further scientific and technological challenges in this field are also summarized. Critical remark and future steps towards the ultimate surface stress-based biosensors are addressed. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Switchable Hydrophobic-Hydrophilic Surfaces

    CERN Document Server

    Bunker, B C; Huber, D L; Kent, M S; Kushmerick, J G; Lopez, G P; Manginell, R P; Méndez, S E; Yim, H


    Tethered films of poly n-isopropylacrylamide (PNIPAM) films have been developed as materials that can be used to switch the chemistry of a surface in response to thermal activation. In water, PNIPAM exhibits a thermally-activated phase transition that is accompanied by significant changes in polymer volume, water contact angle, and protein adsorption characteristics. New synthesis routes have been developed to prepare PNIPAM films via in-situ polymerization on self-assembled monolayers. Swelling transitions in tethered films have been characterized using a wide range of techniques including surface plasmon resonance, attenuated total reflectance infrared spectroscopy, interfacial force microscopy, neutron reflectivity, and theoretical modeling. PNIPAM films have been deployed in integrated microfluidic systems. Switchable PNIPAM films have been investigated for a range of fluidic applications including fluid pumping via surface energy switching and switchable protein traps for pre-concentrating and separating...

  14. Surface motility of Myxococcus Xanthus (United States)

    Gibiansky, Maxsim; Hu, William; Jin, Fan; Zhao, Kun; Shi, Wenyuan; Wong, Gerard


    We examine the surface motility of Myxococcus Xanthus, a bacterium species found in soil that exhibits a broad range of self-organizing behavior, including predatory ``swarms'' and survival-enhancing ``fruiting bodies.'' To quantify the effects of exopolysaccharides (EPS) on surface adhesion and motility, we use modified versions of particle tracking algorithms from colloid physics to analyze bacterial trajectories, and compare the wild type (WT) strain to EPS knockout and EPS overproducer strains. We find that EPS deficiency leads to an increase in the number of ``standing'' bacteria oriented normal to the surface, attached by one end with minimal motility. EPS overproduction, by contrast, suppresses this phenotype. A detailed investigation of the influence of EPS on Myxococcus social motility will be presented.

  15. [Surface layers of methanotrophic bacteria]. (United States)

    Khmelenina, V N; Suzina, N E; Trotsenko, Iu A


    Structural and functional characteristics of the regular glycoprotein layers in prokaryotes are analyzed with a special emphasis on aerobic methanotrophic bacteria. S-layers are present at the surfaces of Methylococcus, Methylothermus, and Methylomicrobium cells. Different Methylomicrobium species either synthesize S-layers with planar (p2, p4) symmetry or form cup-shaped or conicalstructures with hexagonal (p6) symmetry. A unique, copper-binding polypeptide 'CorA'/MopE (27/45 kDa), which is coexpressed with the diheme periplasmic cytochrome c peroxidase 'CorB'/Mca (80 kDa) was found in Methylomicrobium album BG8, Methylomicrobium alcaliphilum 20Z, and Methylococcus capsulatus Bath. This tandem of the surface proteins is functionally analogous to a new siderophore, methanobactin. Importantly, no 'CorA'/MopE homologue was found in methanotrophs not forming S-layers. The role of surface proteins in copper metabolism and initial methane oxidation is discussed.

  16. Sound radiation from finite surfaces

    DEFF Research Database (Denmark)

    Brunskog, Jonas


    A method to account for the effect of finite size in acoustic power radiation problem of planar surfaces using spatial windowing is developed. Cremer and Heckl presents a very useful formula for the power radiating from a structure using the spatially Fourier transformed velocity, which combined...... with spatially windowing of a plane waves can be used to take into account the finite size. In the present paper, this is developed by means of a radiation impedance for finite surfaces, that is used instead of the radiation impedance for infinite surfaces. In this way, the spatial windowing is included...... in the radiation formula directly, and no pre-windowing is needed. Examples are given for the radiation efficiency, and the results are compared with results found in the literature....

  17. Surface flow measurements from drones (United States)

    Tauro, Flavia; Porfiri, Maurizio; Grimaldi, Salvatore


    Drones are transforming the way we sense and interact with the environment. However, despite their increased capabilities, the use of drones in geophysical sciences usually focuses on image acquisition for generating high-resolution maps. Motivated by the increasing demand for innovative and high performance geophysical observational methodologies, we posit the integration of drone technology and optical sensing toward a quantitative characterization of surface flow phenomena. We demonstrate that a recreational drone can be used to yield accurate surface flow maps of sub-meter water bodies. Specifically, drone's vibrations do not hinder surface flow observations, and velocity measurements are in agreement with traditional techniques. This first instance of quantitative water flow sensing from a flying drone paves the way to novel observations of the environment.

  18. Evaluate extended surface exchangers carefully

    Energy Technology Data Exchange (ETDEWEB)

    Ganapathy, V. (ABCO Industries, Inc., Abilene, TX (US))


    Various types of fins, such as circumferential, rectangular, pegs and rods are used in heat transfer equipment. Fins can be used inside as well as on the outside of tubes. However, to illustrate the basic facts of heat transfer and how one should evaluate fins, these discussions pertain to circumferential solid or serrated fins used widely in the energy equipment industry. Extended surfaces have the advantage of reducing the size and weight of heat transfer equipment. In addition they can result in lower gas pressure drop, thus reducing the operating costs. This article compares the performance of an evaporator for a heat recovery steam generator (HRSG) using bare and finned tubes. The fact this article brings out is that extended surfaces should be evaluated and purchased based on performance and not based on surface area alone.

  19. The surface science of enzymes

    DEFF Research Database (Denmark)

    Rod, Thomas Holm; Nørskov, Jens Kehlet


    One of the largest challenges to science in the coming years is to find the relation between enzyme structure and function. Can we predict which reactions an enzyme catalyzes from knowledge of its structure-or from its amino acid sequence? Can we use that knowledge to modify enzyme function......? To solve these problems we must understand in some detail how enzymes interact with reactants from its surroundings. These interactions take place at the surface of the enzyme and the question of enzyme function can be viewed as the surface science of enzymes. In this article we discuss how to describe...... catalysis by enzymes, and in particular the analogies between enzyme catalyzed reactions and surface catalyzed reactions. We do this by discussing two concrete examples of reactions catalyzed both in nature (by enzymes) and in industrial reactors (by inorganic materials), and show that although analogies...

  20. Nanostructured polymer- and metal surfaces

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun

    This Ph.D. thesis explores the optical properties of nanostructured dielectric and metallic surfaces. Focusing on scalable fabrication methods for antireflective nanostructures, this experimental study has resulted in the proof of concept of inexpensive, large area antireflective nanostructures...... in a structural colour filter for specularly transmitted light. By reducing the height and lateral size, the structures enter a regime where scattering of visible light becomes insignificant. In this regime, the BSi structures were shown to be antireflective. An empirical relation between the characteristic...... length scale of the nanostructured surface, and the wavelength at which scattering becomes significant, was shown. The result is thus a design criterion for the use of random nanostructures for non-scattering antireflective surfaces. Antireflective BSi nanostructures were fabricated using injection...

  1. Enhancing cavitation with micromachined surfaces (United States)

    Fernandez Rivas, David; Stricker, Laura; Zijlstra, Aaldert G.; Gardeniers, Han; Lohse, Detlef; Prosperetti, Andrea; Mesoscale Chemical System Group Collaboration; Physics of Fluids Group Collaboration; Department of Mechanical Engineering Collaboration


    When a silicon surface with micromachined pits submerged in a liquid is exposed to continuous ultrasound at 200 kHz, bubbles are ejected from the air filled cavities. Depending on the pressure amplitude different scenarios are observed, as the bubbles ejected from the micropits interact in complex ways with each other, and with the silicon surface. We have determined the size distribution of bubbles ejected from one, two and three pits for three different electrical power settings, and correlated them with sonochemical OH* radical production. Numerical simulations of the sonochemical conversion reaction rates were obtained using the empirical bubble size distributions and are compared with experimental results. Experimental evidence of shock wave emission from the microbubble clusters, deformed microbubble shapes, jetting and surface erosion are also presented. Financially supported through the project 07391 of the Technology Foundation STW, The Netherlands.

  2. Surface plasmons in Drude metals (United States)

    Yelon, A.; Piyakis, K. N.; Sacher, E.


    We present here a detailed derivation of the dispersion relations for surface plasmons in classical Drude metals, taking into account the fact that the relative permittivity at high frequency may be different from 1, as in the case of dielectrics. We also retain the imaginary part of the dielectric response in the derivation of the dispersion relations for the surface plasmon, which exists up to a maximum frequency, ωs. This treatment has not previously been published. We compare the model with experiment, and show the importance of the relative permittivity in understanding the value of ωs in Ag. We show that the observed ratios of surface to volume plasmon peak energies in electron energy loss spectra can be understood in terms of the simple model, but that considerable care is needed in interpreting the physical circumstances of such experiments.

  3. Local excitation of surface plasmon polaritons in random surface nanostructures

    DEFF Research Database (Denmark)

    Bozhevolnyi, S.I.; Volkov, V.S.; Boltasseva, Alexandra


    We investigate local excitation of surface plasmon polaritons (SPPs) at a 55-nm-thick gold layer covered with randomly located scatterers (density similar to75 mum(-2)) by using an uncoated fiber tip of a near-field optical microscope as a radiation source and detecting the radiation scattered...

  4. Adhesion energy, surface traction and surface tension in liquid xenon

    Indian Academy of Sciences (India)


    Nov 27, 2015 ... Home; Journals; Pramana – Journal of Physics; Volume 77; Issue 6. Adhesion energy, surface ... 2 G A Adebayo1. Department of Physics, University of Agriculture, Abeokuta, Nigeria; Department of Pure and Applied Physics, College of Pure and Applied Science, Caleb University, Imota, Lagos, Nigeria ...

  5. Surface composition and surface properties of water hyacinth ...

    African Journals Online (AJOL)

    ... percentage of lignin on the adsorption of volatile polar organic solvents and non-polar n-alkane hydrocarbons is discussed. Key words: Water hyacinth, biomass, surface composition, Fourier Transform Infra-red (FT-IR) spectroscopy, scanning electron microscopy, x-ray diffraction spectroscopy, thermo gravimetric analysis ...

  6. Metal surfaces: Surface, step and kink formation energies

    DEFF Research Database (Denmark)

    Kollár, J.; Vitos, Levente; Johansson, B.


    We review the surface, step, and kink energies in monoatomic metallic systems. A systematic comparison is given between the theoretical results based on density functional theory and available experimental data. Our calculated values are used to predict the equilibrium shapes of small metal...

  7. Surface Plasmon Resonance: An Introduction to a Surface Spectroscopy Technique (United States)

    Tang, Yijun; Zeng, Xiangqun; Liang, Jennifer


    Surface plasmon resonance (SPR) has become an important optical biosensing technology in the areas of biochemistry, biology, and medical sciences because of its real-time, label-free, and noninvasive nature. The high cost of commercial devices and consumables has prevented SPR from being introduced in the undergraduate laboratory. Here, we present…

  8. Bioinspired Surface Treatments for Improved Decontamination: Icephobic Surfaces (United States)


    diameter; Phenomenex, Torrance, CA) with an isocratic 45:55 acetonitrile: 1% aqueous acetic acid mobile phase (1.2 mL/min). [3] For analysis of methyl...paraoxon, methyl salicylate , dimethyl methylphosphate, and diisopropyl fluorophosphates following treatment of contaminated surfaces with a soapy...

  9. Organic-inorganic surface modifications for titanium implant surfaces.

    NARCIS (Netherlands)

    Jonge, L.T. de; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Jansen, J.A.


    This paper reviews current physicochemical and biochemical coating techniques that are investigated to enhance bone regeneration at the interface of titanium implant materials. By applying coatings onto titanium surfaces that mimic the organic and inorganic components of living bone tissue, a

  10. On the surface of superfluids (United States)

    Armas, Jay; Bhattacharya, Jyotirmoy; Jain, Akash; Kundu, Nilay


    Developing on a recent work on localized bubbles of ordinary relativistic fluids, we study the comparatively richer leading order surface physics of relativistic superfluids, coupled to an arbitrary stationary background metric and gauge field in 3 + 1 and 2 + 1 dimensions. The analysis is performed with the help of a Euclidean effective action in one lower dimension, written in terms of the superfluid Goldstone mode, the shape-field (characterizing the surface of the superfluid bubble) and the background fields. We find new terms in the ideal order constitutive relations of the superfluid surface, in both the parity-even and parity-odd sectors, with the corresponding transport coefficients entirely fixed in terms of the first order bulk transport coefficients. Some bulk transport coefficients even enter and modify the surface thermodynamics. In the process, we also evaluate the stationary first order parity-odd bulk currents in 2 + 1 dimensions, which follows from four independent terms in the superfluid effective action in that sector. In the second part of the paper, we extend our analysis to stationary surfaces in 3 + 1 dimensional Galilean superfluids via the null reduction of null superfluids in 4 + 1 dimensions. The ideal order constitutive relations in the Galilean case also exhibit some new terms similar to their relativistic counterparts. Finally, in the relativistic context, we turn on slow but arbitrary time dependence and answer some of the key questions regarding the time-dependent dynamics of the shape-field using the second law of thermodynamics. A linearized fluctuation analysis in 2 + 1 dimensions about a toy equilibrium configuration reveals some new surface modes, including parity-odd ones. Our framework can be easily applied to model more general interfaces between distinct fluid-phases.

  11. Surface rheology and interface stability.

    Energy Technology Data Exchange (ETDEWEB)

    Yaklin, Melissa A.; Cote, Raymond O.; Moffat, Harry K.; Grillet, Anne Mary; Walker, Lynn; Koehler, Timothy P.; Reichert, Matthew D. (Carnegie Mellon University, Pittsburgh, PA); Castaneda, Jaime N.; Mondy, Lisa Ann; Brooks, Carlton, F.


    We have developed a mature laboratory at Sandia to measure interfacial rheology, using a combination of home-built, commercially available, and customized commercial tools. An Interfacial Shear Rheometer (KSV ISR-400) was modified and the software improved to increase sensitivity and reliability. Another shear rheometer, a TA Instruments AR-G2, was equipped with a du Nouey ring, bicone geometry, and a double wall ring. These interfacial attachments were compared to each other and to the ISR. The best results with the AR-G2 were obtained with the du Nouey ring. A Micro-Interfacial Rheometer (MIR) was developed in house to obtain the much higher sensitivity given by a smaller probe. However, it was found to be difficult to apply this technique for highly elastic surfaces. Interfaces also exhibit dilatational rheology when the interface changes area, such as occurs when bubbles grow or shrink. To measure this rheological response we developed a Surface Dilatational Rheometer (SDR), in which changes in surface tension with surface area are measured during the oscillation of the volume of a pendant drop or bubble. All instruments were tested with various surfactant solutions to determine the limitations of each. In addition, foaming capability and foam stability were tested and compared with the rheology data. It was found that there was no clear correlation of surface rheology with foaming/defoaming with different types of surfactants, but, within a family of surfactants, rheology could predict the foam stability. Diffusion of surfactants to the interface and the behavior of polyelectrolytes were two subjects studied with the new equipment. Finally, surface rheological terms were added to a finite element Navier-Stokes solver and preliminary testing of the code completed. Recommendations for improved implementation were given. When completed we plan to use the computations to better interpret the experimental data and account for the effects of the underlying bulk

  12. Mars Surface Tunnel Element Concept (United States)

    Rucker, Michelle A.


    How crews get into or out of their ascent vehicle has profound implications for Mars surface architecture. Extravehicular Activity (EVA) hatches and Airlocks have the benefit of relatively low mass and high Technology Readiness Level (TRL), but waste consumables with a volume depressurization for every ingress/egress. Perhaps the biggest drawback to EVA hatches or Airlocks is that they make it difficult to keep Martian dust from being tracked back into the ascent vehicle, in violation of planetary protection protocols. Suit ports offer the promise of dust mitigation by keeping dusty suits outside the cabin, but require significant cabin real estate, are relatively high mass, and current operational concepts still require an EVA hatch to get the suits outside for the first EVA, and back inside after the final EVA. This is primarily because current designs don't provide enough structural support to protect the suits from ascent/descent loads or potential thruster plume impingement. For architectures involving more than one surface element-such as an ascent vehicle and a rover or surface habitat-a retractable tunnel is an attractive option. By pushing spacesuit don/doff and EVA operations to an element that remains on the surface, ascended vehicle mass and dust can be minimized. What's more, retractable tunnels provide operational flexibility by allowing surface assets to be re-configured or built up over time. Retractable tunnel functional requirements and design concepts being developed as part of the National Aeronautics and Space Administration's (NASA) Evolvable Mars Campaign (EMC) work will add a new ingress/egress option to the surface architecture trade space.

  13. Surface modification agents for lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zonghai; Amine, Khalil; Belharouak, Ilias


    An active material for an electrochemical device wherein a surface of the active material is modified by a surface modification agent, wherein the surface modification agent is an organometallic compound.

  14. Voigt Airy surface magneto plasmons. (United States)

    Hu, Bin; Wang, Qi Jie; Zhang, Ying


    We present a basic theory on Airy surface magneto plasmons (SMPs) at the interface between a dielectric layer and a metal layer (or a doped semiconductor layer) under an external static magnetic field in the Voigt configuration. It is shown that, in the paraxial approximation, the Airy SMPs can propagate along the surface without violating the nondiffracting characteristics, while the ballistic trajectory of the Airy SMPs can be tuned by the applied magnetic field. In addition, the self-deflection-tuning property of the Airy SMPs depends on the direction of the external magnetic field applied, owing to the nonreciprocal effect.

  15. Cold atoms close to surfaces

    DEFF Research Database (Denmark)

    Krüger, Peter; Wildermuth, Stephan; Hofferberth, Sebastian


    Microscopic atom optical devices integrated on atom chips allow to precisely control and manipulate ultra-cold (T atoms and Bose-Einstein condensates (BECs) close to surfaces. The relevant energy scale of a BEC is extremely small (down to ... be utilized as a sensor for variations of the potential energy of the atoms close to the surface. Here we describe how to use trapped atoms as a measurement device and analyze the performance and flexibility of the field sensor. We demonstrate microscopic magnetic imaging with simultaneous high spatial...

  16. Structure of the moon's surface

    CERN Document Server

    Fielder, Gilbert


    Structure of the Moon's Surface aims to assemble and marshal relevant matter, and to produce a largely unprejudiced text which brings lunar studies up to date and stresses the importance of certain features of the Moon which have frequently been disregarded in the past, largely because of lack of knowledge about them. The book contains 14 chapters organized into two parts. Part I reviews and summarizes important physical problems. These include the liberations of the moon; height determinations of points of the moon's surface; the figure of the moon; and the moon's temperature and atmosphere.

  17. Method of passivating semiconductor surfaces (United States)

    Wanlass, M.W.


    A method is described for passivating Group III-V or II-VI semiconductor compound surfaces. The method includes selecting a passivating material having a lattice constant substantially mismatched to the lattice constant of the semiconductor compound. The passivating material is then grown as an ultrathin layer of passivating material on the surface of the Group III-V or II-VI semiconductor compound. The passivating material is grown to a thickness sufficient to maintain a coherent interface between the ultrathin passivating material and the semiconductor compound. In addition, a device formed from such method is also disclosed.

  18. Interactive Design of Developable Surfaces

    KAUST Repository

    Tang, Chengcheng


    We present a new approach to geometric modeling with developable surfaces and the design of curved-creased origami. We represent developables as splines and express the nonlinear conditions relating to developability and curved folds as quadratic equations. This allows us to utilize a constraint solver, which may be described as energy-guided projection onto the constraint manifold, and which is fast enough for interactive modeling. Further, a combined primal-dual surface representation enables us to robustly and quickly solve approximation problems.

  19. Surface Characterization of New Biomaterials (United States)

    Minciuna, M. G.; Vizureanu, P.; Abdullah, M. M. B.; Achitei, D. C.; Istrate, B.; Cimpoesu, R.; Focsaneanu, S. C.


    This paper presents the characterization of new alloys CoCrMoSi6, CoCrMoSi7, CoCrMoSi10, in terms of hardness determinations, fractographic analysis and surface analysis. The original version of the alloy was obtained by casting process in a vacuum arc furnace. Experimental results obtained from this study confirms that by increasing content of silicon, the mechanical properties are superior and the positive results obtained at surface studies favoring the formation of compounds, that lead to the reduction of alloying grade for α solid solution and the plasticity of the alloys.

  20. Collaboration Meets Interactive Surfaces (CMIS)

    DEFF Research Database (Denmark)

    Anslow, Craig; Campos, Pedro; Grisoni, Laurent


    This workshop proposes to bring together researchers who are interested in improving collaborative experiences through the combination of multiple interaction surfaces with diverse sizes and formats, ranging from large-scale walls, to tables, mobiles, and wearables. The opportunities for innovation...... exist, but the ITS, CHI, CSCW, and other HCI communities have not yet thoroughly addressed the problem of bringing effective collaboration activities together using multiple interactive surfaces, especially in complex work domains. Of particular interest is the potential synergy that one can obtain...

  1. Surface coil magnetic resonance imaging. (United States)

    Axel, L; Hayes, C


    Detection of MR signals with surface coils provides increased signal-to-noise ratio for superficial structures relative to detection by circumferential coils, permitting improved spatial resolution. Different geometries of surface coils can be used for different regions. Coils that are flat or curved to fit body contours are good for general imaging, with a range of coil sizes useful for structures of different size or depth. Solenoidal coils are useful for imaging protruding structures such as breasts, while smaller versions of conventional circumferential coils that can be slipped over limbs are useful for imaging extremities.

  2. Narcissus of diffrative optical surfaces (United States)

    Cohen, Jonathan B.


    Narcissus is usually approximated by means of a paraxial ray trace through the optical system in the ordinary direction of light travel. An accurate calculation involves tracing real rays backwards from the detector to the reflecting surface, and back to the detector after reflection. It is shown that the diffractive order of maximum efficiency for a diffractive optical surface is different for transmitted and reflected radiation. This precludes the use of the paraxial approximation for calculating the effect of narcissus. The real ray method of calculation must be used with specific orders of diffraction based on their efficiencies.

  3. Surface modification to prevent oxide scale spallation

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A


    A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

  4. Innovative Deterministic Optical Surface Finishing Project (United States)

    National Aeronautics and Space Administration — Increasing the optical surface finishing precision and reducing surface roughness will greatly benefit astronomy telescope and other optical systems. Conventional...

  5. Surface properties of 3d transition metals (United States)

    Punkkinen, M. P. J.; Hu, Q.-M.; Kwon, S. K.; Johansson, B.; Kollár, J.; Vitos, L.


    Using the projector augmented wave method within density functional theory, we present a systematic study of the layer relaxation, surface energy and surface stress of 3d transition metals. Comparing the calculated trends for the surface energy and stress with those obtained for 4d and 5d metals we find that magnetism has a significant effect on the surface properties. Enhanced surface magnetic moments decrease the size of the surface relaxation, lower the surface energy and surface stress, leading to compressive stress in Cr and Mn.

  6. Quantitative Characterisation of Surface Texture

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Lonardo, P.M.; Trumpold, H.


    This paper reviews the different methods used to give a quantitative characterisation of surface texture. The paper contains a review of conventional 2D as well as 3D roughness parameters, with particular emphasis on recent international standards and developments. It presents new texture...

  7. Nitrogen interactions at metal surfaces

    NARCIS (Netherlands)

    Gleeson, M. A.; Kleyn, A. W.


    Molecular beam experiments with specially prepared beams allow the study of the interaction of very reactive species with surfaces. In the present case the interaction of N-atoms with Ag(1 1 1) is studied. The energy of the atoms is around 5 eV, precisely between the classical energy regimes of

  8. Critical behavior of collapsing surfaces

    DEFF Research Database (Denmark)

    Olsen, Kasper; Sourdis, C.


    We consider the mean curvature evolution of rotationally symmetric surfaces. Using numerical methods, we detect critical behavior at the threshold of singularity formation resembling that of gravitational collapse. In particular, the mean curvature simulation of a one-parameter family of initial...

  9. Nonlinear surface waves over topography

    NARCIS (Netherlands)

    Janssen, T.T.


    As ocean surface waves radiate into shallow coastal areas and onto beaches, their lengths shorten, wave heights increase, and the wave shape transforms from nearsinusoidal to the characteristic saw-tooth shapes at the onset of breaking; in the ensuing breaking process the wave energy is cascaded to

  10. Surface chemistry in three dimensions

    DEFF Research Database (Denmark)

    Bollinger, Mikkel; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet


    the usual single surface ('2D') process because indirect adsorbate-adsorbate interactions in the transition state are absent in the '3D' case. The prospects for STM-induced single molecule chemistry and for '3D' catalysts are discussed. (C) 2000 Elsevier Science B.V. All rights reserved....

  11. Growth of rough epitaxial surfaces

    Indian Academy of Sciences (India)

    Among various physical processes which have been taken into account in models of growing interfaces, surface diffusion has been considered as the most important process involved. One such model involves the linear fourth-order Mullins–Herring continuum equation [10,11] supported by the discrete model of Wolf and ...

  12. Immunoglobulin adsorption on modified surfaces

    NARCIS (Netherlands)

    Bremer, M.G.E.G.


    Preservation of biological functioning of proteins during immobilisation is of special interest in various biomedical and biotechnical applications. In industry physical adsorption of immunoglobulins (IgGs) onto solid surfaces is still the predominant immobilisation procedure because it is

  13. Dimple Patterns in Buckling Surfaces (United States)

    Breid, Derek; Crosby, Alfred


    Surface wrinkling has attracted considerable attention in recent years for its ability to generate micro- and nano- scale surface structures via non-lithographic pathways. Although the wrinkle morphology has been considered from an energetic viewpoint for stresses exceeding the critical bifurcation stress, the wrinkle morphology for stress near the critical value is far less understood, in part due to a lack of experimental results in this regime. Recent models for this regime predict the formation of a dimple-phase morphology when the stress is equibiaxial, transitioning to aligned ridges when the stress is anisotropic. Here, we present an experimental investigation into the formation of dimple arrays through the control of the applied stress as well as the geometric parameters of the wrinkling system. We demonstrate the ability to develop dimple arrays over extensive lateral length scales, as well as dimples on the surface of a microscale hemisphere, resulting in a `golf ball' hierarchical structure. These results shed light on the morphology in the near-critical wrinkle regime and provoke many open questions about the underlying materials mechanics in the development of wrinkle surface structures.

  14. Surface Modification of Catalytic Materials

    DEFF Research Database (Denmark)

    Nierhoff, Anders Ulrik Fregerslev

    aggregation techniques. With the use of two different filter mechanisms, the Quadrupole and the Lateral Time Of Flight, the nanoparticles were mass selected. This was done to correlate nanoparticle size with reactivity. Selected key findings can be summarized as: 1) CO induced surface changes of Pt based...

  15. Temperature dependence of surface nanobubbles

    NARCIS (Netherlands)

    Berkelaar, R.P.; Seddon, James Richard Thorley; Zandvliet, Henricus J.W.; Lohse, Detlef


    The temperature dependence of nanobubbles was investigated experimentally using atomic force microscopy. By scanning the same area of the surface at temperatures from 51 °C to 25 °C it was possible to track geometrical changes of individual nanobubbles as the temperature was decreased.

  16. Surface chemistry of "unprotected" nanoparticles

    DEFF Research Database (Denmark)

    Schrader, Imke; Warneke, Jonas; Neumann, Sarah


    spectroscopy reveals that the CO coverage increases as the NaOH concentration used in the precursor solution is decreased. However, even at the lowest for the synthesis suitable OH- concentration the surface was found to be covered by both species. Finally, the effect of the OH...

  17. Nanofriction: Skating on hot surfaces (United States)

    Meyer, Ernst; Gnecco, Enrico


    Simulations of nanoscale sharp tips sliding on a salt surface predict vanishing friction at temperatures close to the melting temperature, as the tip skates on a layer of liquefied salt. This insight opens the way to applications in MEMS, NEMS and auto/aerospace engines.

  18. A Course on Surface Phenomena. (United States)

    Woods, Donald R.


    Describes a graduate or senior elective course combining fundamentals of surface phenomena with practical problem-solving structured around a series of case problems. Discusses topics covered and their development through acquiring new knowledge applied to the case problem, practical calculations of solutions, and applications to additional…

  19. Surface meshing with curvature convergence

    KAUST Repository

    Li, Huibin


    Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

  20. Rowing faster by surface treatment

    NARCIS (Netherlands)

    Greidanus, A.J.; Delfos, R.; Westerweel, J.


    The largest part of hydrodynamic drag during rowing, sailing or canoeing is the turbulent skin friction (80-90%). Higher velocities can be achieved by reducing the friction drag as a result of surface treatment. This research focuses on the development, characterization, and testing of drag-reducing

  1. Surface shape memory in polymers (United States)

    Mather, Patrick


    Many crosslinked polymers exhibit a shape memory effect wherein a permanent shape can be prescribed during crosslinking and arbitrary temporary shapes may be set through network chain immobilization. Researchers have extensively investigated such shape memory polymers in bulk form (bars, films, foams), revealing a multitude of approaches. Applications abound for such materials and a significant fraction of the studies in this area concern application-specific characterization. Recently, we have turned our attention to surface shape memory in polymers as a means to miniaturization of the effect, largely motivated to study the interaction of biological cells with shape memory polymers. In this presentation, attention will be given to several approaches we have taken to prepare and study surface shape memory phenomenon. First, a reversible embossing study involving a glassy, crosslinked shape memory material will be presented. Here, the permanent shape was flat while the temporary state consisted of embossed parallel groves. Further the fixing mechanism was vitrification, with Tg adjusted to accommodate experiments with cells. We observed that the orientation and spreading of adherent cells could be triggered to change by the topographical switch from grooved to flat. Second, a functionally graded shape memory polymer will be presented, the grading being a variation in glass transition temperature in one direction along the length of films. Characterization of the shape fixing and recovery of such films utilized an indentation technique that, along with polarizing microscopy, allowed visualization of stress distribution in proximity to the indentations. Finally, very recent research concerning shape memory induced wrinkle formation on polymer surfaces will be presented. A transformation from smooth to wrinkled surfaces at physiological temperatures has been observed to have a dramatic effect on the behavior of adherent cells. A look to the future in research and

  2. Surfaces of forced vergence disparity

    Directory of Open Access Journals (Sweden)

    A. Rubin


    Full Text Available Purpose: To introduce the concept of surfaces offorced vergence disparity using measurementsof fixation disparity from three young, healthy individuals.Method: Fixation disparities were measured in three individuals in relation to variation in stimulus distance and vergence demand.  All measurementswere obtained by means of the Sheedy disparometerwhich can be used to measure not only fixation disparity but also associated phorias.  For each individual, consecutive measurements of fixation disparity only were determined over a short time period at four stimulus distances (0.25 m, 0.4 m, 1 m and 2 m and under five different vergence demands as produced with the application of different amounts of prism (either base in or base out and also without any prism.  Parametric and non-parametric statistical methods are used to understand short-term variation of fixation disparity and pseudo-3D and stereo-pairs represent thesurfaces of forced vergence disparity with which this paper is mainly concerned.Results:  Surfaces of forced vergence disparity are very useful to study variation of fixation disparity inrelation to change in stimulus distance and vergence demand.  They are effectively 3-dimensional equivalents of 2-dimensional Ogle curves of forcedvergence disparity.Conclusion: Surfaces of forced vergence disparity may be useful in many contexts - both in relation to normal or unusual binocular behaviour.  This paper introduces such surfaces in relation to three individuals who were considered as having satisfactory binocular and accommodative-vergence function.  The surfaces assist one in understanding complicated three-dimensional or trivariate data that involves fixation disparities, different stimulus locations and different accommodative-vergence demands upon the oculo-motor system.  (S Afr Optom 2013 72(1 25-33 

  3. Replication of micro and nano surface geometries

    DEFF Research Database (Denmark)

    Hansen, Hans Nørgaard; Hocken, R.J.; Tosello, Guido


    The paper describes the state-of-the-art in replication of surface texture and topography at micro and nano scale. The description includes replication of surfaces in polymers, metals and glass. Three different main technological areas enabled by surface replication processes are presented......: manufacture of net-shape micro/nano surfaces, tooling (i.e. master making), and surface quality control (metrology, inspection). Replication processes and methods as well as the metrology of surfaces to determine the degree of replication are presented and classified. Examples from various application areas...... are given including replication for surface texture measurements, surface roughness standards, manufacture of micro and nano structured functional surfaces, replicated surfaces for optical applications (e.g. optical gratings), and process chains based on combinations of repeated surface replication steps....

  4. On real structures on rigid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kulikov, Vik S [Steklov Mathematical Institute, Russian Academy of Sciences (Russian Federation); Kharlamov, V M [Institut de Recherche Matematique Avanee Universite Louis Pasteur et CNRS 7 rue Rene Descartes (France)


    We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p{sub g}=q=0 and K{sup 2}=9. These surfaces also provide new counterexamples to the 'Dif = Def' problem.

  5. Surface plasmons on nanostructured metal-dielectric surfaces (United States)

    Ćtyroký, Jiří


    Surface plasmons-polaritons (or briefly, surface plasmons, SP) have been intensively investigated as potential information carriers for ultra-small photonic (plasmonic) devices and circuits. SPs can be confined in subwavelength regions, but their propagation is inherently lossy due to free-carrier absorption in metals. Thus, the proper balance between confinement and loss is the basic problem in the design of plasmonic waveguides and devices. This work is devoted to the analysis of waveguiding properties of plasmonic structures in which a homogeneous (bulk) metal is replaced with mutually interlaced metal and dielectric layers with deeply subwavelength thicknesses. Approaches based on effective medium theory and rigorous electromagnetic analysis are presented and mutually compared.

  6. Surface science studies of Cobalt and Rhodium single crystal surfaces


    Ramsvik, Trond


    The main topic of this thesis is the investigation of small molecules adsorbed on the transition metals cobalt and rhodium surfaces by means of predominantly high-resolution core level photoemission and near edge x-ray absorption fine structure (NEXAFS). The thesis can be divided into three parts where the following phenomena are examined: 1) internal molecular vibrations in the core level photoemission spectra 2) hybridisation and thermal decomposition of adsorbates 3) growth and...

  7. PREFACE: Atom-surface scattering Atom-surface scattering (United States)

    Miret-Artés, Salvador


    It has been a privilege and a real pleasure to organize this special issue or festschrift in the general field of atom-surface scattering (and its interaction) in honor of J R Manson. This is a good opportunity and an ideal place to express our deep gratitude to one of the leaders in this field for his fundamental and outstanding scientific contributions. J R Manson, or Dick to his friends and colleagues, is one of the founding fathers, together with N Cabrera and V Celli, of the 'Theory of surface scattering and detection of surface phonons'. This is the title of the very well-known first theoretical paper by Dick published in Physical Review Letters in 1969. My first meeting with Dick was around twenty years ago in Saclay. J Lapujoulade organized a small group seminar about selective adsorption resonances in metal vicinal surfaces. We discussed this important issue in surface physics and many other things as if we had always known each other. This familiarity and warm welcome struck me from the very beginning. During the coming years, I found this to be a very attractive aspect of his personality. During my stays in Göttingen, we had the opportunity to talk widely about science and life at lunch or dinner time, walking or cycling. During these nice meetings, he showed, with humility, an impressive cultural background. It is quite clear that his personal opinions about history, religion, politics, music, etc, come from considering and analyzing them as 'open dynamical systems'. In particular, with good food and better wine in a restaurant or at home, a happy cheerful soirée is guaranteed with him, or even with only a good beer or espresso, and an interesting conversation arises naturally. He likes to listen before speaking. Probably not many people know his interest in tractors. He has an incredible collection of very old tractors at home. In one of my visits to Clemson, he showed me the collection, explaining to me in great detail, their technical properties

  8. Drag force and surface roughness measurements on freshwater biofouled surfaces. (United States)

    Andrewartha, J; Perkins, K; Sargison, J; Osborn, J; Walker, G; Henderson, A; Hallegraeff, G


    The detrimental effect of biofilms on skin friction for near wall flows is well known. The diatom genera Gomphonema and Tabellaria dominated the biofilm mat in the freshwater open channels of the Tarraleah Hydropower Scheme in Tasmania, Australia. A multi-faceted approach was adopted to investigate the drag penalty for biofouled 1.0 m x 0.6 m test plates which incorporated species identification, drag measurement in a recirculating water tunnel and surface characterisation using close-range photogrammetry. Increases in total drag coefficient of up to 99% were measured over clean surface values for biofouled test plates incubated under flow conditions in a hydropower canal. The effective roughness of the biofouled surfaces was found to be larger than the physical roughness; the additional energy dissipation was caused in part by the vibration of the biofilms in three-dimensions under flow conditions. The data indicate that there was a roughly linear relationship between the maximum peak-to-valley height of a biofilm and the total drag coefficient.

  9. Role of electric field on surface wetting of polystyrene surface. (United States)

    Bhushan, Bharat; Pan, Yunlu


    The role of surface charge in fluid flow in micro/nanofluidics systems as well as the role of electric field to create switchable hydrophobic surfaces is of interest. In this work, the contact angle (CA) and contact angle hysteresis (CAH) of a droplet of deionized (DI) water were measured with applied direct current (DC) and alternating current (AC) electric fields. The droplet was deposited on a polystyrene (PS) surface, commonly used in various nanotechnology applications, coated on a doped silicon (Si) wafer. With the DC field, CA decreased with an increase in voltage. Because of the presence of a silicon oxide layer and a space charge layer, the change of the CA was found to be lower than with a metal substrate. The CAH had no obvious change with a DC field. An AC field with a positive value was applied to the droplet to study its effect on CA and CAH. At low frequency (lower than 10 Hz), the droplet was visibly oscillating. The CA was found to increase when the frequency of the applied AC field increased from 1 Hz to 10 kHz. On the other hand, the CA decreased with an increasing peak-peak voltage at or lower than 10 kHz. The CAH in the AC field was found to be lower than in the DC field and had a similar trend to static CA with increasing frequency. A model is presented to explain the data.

  10. A surface definition code for turbine blade surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S L [Michigan Technological Univ., Houghton, MI (United States); Oryang, D; Ho, M J [Tuskegee Univ., AL (United States)


    A numerical interpolation scheme has been developed for generating the three-dimensional geometry of wind turbine blades. The numerical scheme consists of (1) creating the frame of the blade through the input of two or more airfoils at some specific spanwise stations and then scaling and twisting them according to the prescribed distributions of chord, thickness, and twist along the span of the blade; (2) transforming the physical coordinates of the blade frame into a computational domain that complies with the interpolation requirements; and finally (3) applying the bi-tension spline interpolation method, in the computational domain, to determine the coordinates of any point on the blade surface. Detailed descriptions of the overall approach to and philosophy of the code development are given along with the operation of the code. To show the usefulness of the bi-tension spline interpolation code developed, two examples are given, namely CARTER and MICON blade surface generation. Numerical results are presented in both graphic data forms. The solutions obtained in this work show that the computer code developed can be a powerful tool for generating the surface coordinates for any three-dimensional blade.

  11. Evaluation of Surface Fatigue Strength Based on Surface Temperature (Surface Temperature Calculation for Rolling-Sliding Contact)


    鄧, 鋼; 中西, 勉


    Surface temperature is considered as an integrated index which is a combined result of not only the load and dimensions at the contact point but also the sliding velocity, rolling velocity, surface roughness, lubrication condition and etc.. So, the surface durability of such as roller and gear will be evaluated more exactly and simply by use of the surface temperature than Hertzian stress. In this research, the surface temperatures of rollers under different rolling and sliding conditions are...

  12. Determination of retinal surface area. (United States)

    Nagra, Manbir; Gilmartin, Bernard; Thai, Ngoc Jade; Logan, Nicola S


    Previous attempts at determining retinal surface area and surface area of the whole eye have been based upon mathematical calculations derived from retinal photographs, schematic eyes and retinal biopsies of donor eyes. 3-dimensional (3-D) ocular magnetic resonance imaging (MRI) allows a more direct measurement, it can be used to image the eye in vivo, and there is no risk of tissue shrinkage. The primary purpose of this study is to compare, using T2-weighted 3D MRI, retinal surface areas for superior-temporal (ST), inferior-temporal (IT), superior-nasal (SN) and inferior-nasal (IN) retinal quadrants. An ancillary aim is to examine whether inter-quadrant variations in area are concordant with reported inter-quadrant patterns of susceptibility to retinal breaks associated with posterior vitreous detachment (PVD). Seventy-three adult participants presenting without retinal pathology (mean age 26.25 ± 6.06 years) were scanned using a Siemens 3-Tesla MRI scanner to provide T2-weighted MR images that demarcate fluid-filled internal structures for the whole eye and provide high-contrast delineation of the vitreous-retina interface. Integrated MRI software generated total internal ocular surface area (TSA). The second nodal point was used to demarcate the origin of the peripheral retina in order to calculate total retinal surface area (RSA) and quadrant retinal surface areas (QRSA) for ST, IT, SN, and IN quadrants. Mean spherical error (MSE) was -2.50 ± 4.03D and mean axial length (AL) 24.51 ± 1.57 mm. Mean TSA and RSA for the RE were 2058 ± 189 and 1363 ± 160 mm2 , respectively. Repeated measures anova for QRSA data indicated a significant difference within-quadrants (P area/mm increase in AL. Although the differences between QRSAs are relatively small, there was evidence of concordance with reported inter-quadrant patterns of susceptibility to retinal breaks associated with PVD. The data allow AL to be converted to QRSAs, which will assist further

  13. Solar Surface Magneto-Convection

    Directory of Open Access Journals (Sweden)

    Robert F. Stein


    Full Text Available We review the properties of solar magneto-convection in the top half of the convection zones scale heights (from 20 Mm below the visible surface to the surface, and then through the photosphere to the temperature minimum. Convection is a highly non-linear and non-local process, so it is best studied by numerical simulations. We focus on simulations that include sufficient detailed physics so that their results can be quantitatively compared with observations. The solar surface is covered with magnetic features with spatial sizes ranging from unobservably small to hundreds of megameters. Three orders of magnitude more magnetic flux emerges in the quiet Sun than emerges in active regions. In this review we focus mainly on the properties of the quiet Sun magnetic field. The Sun’s magnetic field is produced by dynamo action throughout the convection zone, primarily by stretching and twisting in the turbulent downflows. Diverging convective upflows and magnetic buoyancy carry magnetic flux toward the surface and sweep the field into the surrounding downflow lanes where the field is dragged downward. The result is a hierarchy of undulating magnetic Ω- and U-loops of different sizes. New magnetic flux first appears at the surface in a mixed polarity random pattern and then collects into isolated unipolar regions due to underlying larger scale magnetic structures. Rising magnetic structures are not coherent, but develop a filamentary structure. Emerging magnetic flux alters the convection properties, producing larger, darker granules. Strong field concentrations inhibit transverse plasma motions and, as a result, reduce convective heat transport toward the surface which cools. Being cooler, these magnetic field concentrations have a shorter scale height and become evacuated. The field becomes further compressed and can reach strengths in balance with the surrounding gas pressure. Because of their small internal density, photons escape from deeper in

  14. Surface Electromigration and Current Crowding (United States)

    Yongsunthon, R.; Tao, C.; Rous, P.; Williams, E. D.

    Steps on macroscopic surfaces provide a useful model system for quantifying electron scattering at defects in nanostructures, where the large surface/volume ratio will cause surface effects to dominate. Here, the effects of electron scattering at surface steps are quantified using thin silver films with (111) surface orientation. Using real-time scanning tunneling microscopy (STM) measurements while large current densities are applied to the films, changes in step fluctuations and island motion are observed and quantified. Applying the tools of the continuum step model, the observations are analyzed in terms of step free energies and kinetics, yielding quantitative values of the electromigration force driving the observed mass displacements. The derived magnitudes are surprisingly large in comparison with classical calculations of the force due to electron scattering at the internal surface of a conductor. This result indicates that the specific atomistic characteristics of the scattering sites, in this case kinks at the step edge, may greatly enhance the electromigration force. Within the classical ballistic picture of ballistic momentum transfer, specific mechanisms for such enhancement include enhanced geometric "blocking" at the kinked step edges, changes in carrier density near kinks, and current crowding. Quantum transmission effects at atomic-scale defect sites may also be responsible for the observed enhancement. The nature of classical current crowding as a function of the shape and size of defect was characterized using magnetic force microscopy (MFM) of fabricated micron-scale model structures. Techniques were developed to remove the effects of instrumental broadening using deconvolution, so that full three-dimensional maps of the magnetic fields above the current line are determined. A Green function inversion technique is then used to invert the field distribution to determine the spatial variations in the current density in the sample. Current

  15. The Ge(0 0 1) surface

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.


    Although germanium (Ge) (0 0 1) has a relatively small surface unit cell, this surface displays a wealth of fascinating phenomena. The Ge(0 0 1) surface is a prototypical example of a system possessing both a strong short-range interaction due to dimerization of the surface atoms, as well as an

  16. A method for texturing a glass surface

    NARCIS (Netherlands)

    Yang, G.; Van Swaaij, R.A.C.M.M.; Isabella, O.


    The present invention relates to a new method of texturing a glass surface. In further aspects, the present invention relates to the resulting textured glass surface; to a photovoltaic device comprising the textured glass surface; and, to use of the textured glass surface for scattering light.

  17. Surface current density K: an introduction

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson


    The author discusses the vector surface of current density K used in electrical insulation studies. K is related to the vector tangential electric field Kt at the surface of a body by the vector equation K=ΓE t where Γ represents the surface conductivity. The author derives a surface continuity...

  18. Surface structure of AU3Cu(001)

    DEFF Research Database (Denmark)

    Eckstein, G.A.; Maupai, S.; Dakkouri, A.S.


    The surface morphology, composition, and structure of Au3Cu(001) as determined by scanning tunneling microscopy and surface x-ray diffraction are presented. Atomic resolution STM images reveal distinctive geometric features. The analysis of the surface x-ray diffraction data provides clear evidence...... for the surface structure. [S0163-1829(99)04535-X]....

  19. Meshing skin surfaces with certified topology

    NARCIS (Netherlands)

    Kruithof, N.G.H.; Vegter, G.


    Skin surfaces are used for the modeling and visualization of molecules. They form a class of tangent continuous surfaces defined in terms of a set of balls (the atoms of the molecule) and a shrink factor More recently, skin surfaces have been used to approximate arbitrary surfaces. We present an

  20. Energy conservation potential of surface modification technologies

    Energy Technology Data Exchange (ETDEWEB)

    Le, H.K.; Horne, D.M.; Silberglitt, R.S.


    This report assesses the energy conservation impact of surface modification technologies on the metalworking industries. The energy conservation impact of surface modification technologies on the metalworking industries is assessed by estimating their friction and wear tribological sinks and the subsequent reduction in these sinks when surface modified tools are used. Ion implantation, coatings, and laser and electron beam surface modifications are considered.