bluuebunny/crossref_metadata_2025 huggingface dataset:
STRUCTURES AND DYNAMICS OF ENDOHEDRAL SCANDIUM METALLOFULLERENES
Authors: SHINOHARA H. , TANSHO M. , INAKUMA M. , SAITO Y. , SATO H. , HAYASHI N. , KATO T. , HASHIZUME T. , SAKURAI T.
Published: October 2004

The endohedral metallofullerenes, such as Sc@C 82, Sc 2@ C 84, and Sc 3@ C 82, have been purified and isolated by using two-stage high-performance liquid chromatography (HPLC). The ESR spectrum of the isolated Sc 3@ C 82 exhibits a perfectly symmetric 22 hyperfined splittings with an inherent linewidth of 0.77 Gauss at 220 K, which is consistent with a unique structure that three scandium atoms are encaged triangularly within the C3v isomer of C 82. In addition, we report the direct imaging of the isolated discandium fullerene ( Sc 2@ C 84) on silicon clean surfaces in an ultrahigh-vacuum environment by utilizing scanning tunneling microscopy (STM). The STM images reveal spherical Sc 2@ C 84 fullerenes, spaced 11.7 Å apart, stacked in close-packed arrays.
SIMPLE APPROACHES TO FULLERENES AND BUCKONIONS ELECTRONIC STRUCTURE: GUTZWILLER AND SHELL-MODEL CALCULATIONS
Authors: TARENTO R.J. , JOYES P. , WALLE J. VAN DE
Published: October 2004

The electronic structure of fullerenes and buckonions have been investigated using quantum-mechanical methods: the Gutzwiller and shell-model techniques. In the first part, fullerenes have been modeled with the Hubbard Hamiltonian and the electronic correlation has been examined within the Gutzwiller framework. It has been derived various characteristic energies of fullerenes ( C 60 and C 240) in the free state (first and second ionization energies, electron affinity, and singlet and triplet energies). The second part deals with buckonions. Fullerenes and buckonions have been modeled with the spherical shell-model approach. The calculation has led to the electronic structure of fullerenes and of buckonions. So if we compare the energy levels of the buckonions with those of the fullerenes which build the buckonions, only the buckonions energy levels coming from the outer shell are changed by the coupling between shells.
MAGNETIC MEASUREMENTS ON YC2 ENCAPSULATED IN GRAPHITIC POLYHEDRAL PARTICLES
Authors: KASUYA A. , IWASAKI H. , SAITO Y. , OKUDA M. , TAKAHASHI H. , SUEZAWA M. , SUMIYAMA K. , SUZUKI K. , NISHINA Y.
Published: October 2004

Graphitic polyhedrons encaging YC 2 of 30–70 nm in diameter have been synthesized by an arc-discharge method. Our measurements identify that YC 2 crystallizes in a body-centered tetragonal and becomes type-II superconductor below 3.9 K. The transition temperature shows very small size dependence, and is nearly equal to previous measurements on bulk YC 2 in vacuum. Although YC 2 is hygroscopic, our samples yield reliable and reproducible experimental results in our electron microscope, x-ray diffraction, paramagnetic resonance, and magnetization measurements in air under magnetic field up to 3000 Oe and temperatures down to 1.7 K.
PURIFIED CARBON NANOPARTICLES INVESTIGATED WITH HREM AND RAMAN SPECTROSCOPY
Authors: BACSA W.S. , UGARTE D. , STÖCKLI T. , CHÂTELAIN A. , HEER W.A. DE
Published: October 2004

Previous studies of fullerene-related materials (nanotubes, onions, etc.) have been almost exclusively performed with electron microscopy methods due to the heterogeneous character of the deposits produced in the electric arc. We report Raman spectra of carbon nanotubes which have been purified following the procedure of Ebbesen et al. The purity of the sample has been confirmed by high-resolution electron microscopy. The Raman spectra of carbon nanotubes with an average diameter of 10–12 nm show very little disorder-induced scattering and no curvature-induced phonon softening, in contrast to unpurified material which contains a large number of carbon nanoparticles. These experimental findings are confirmed by lattice-dynamical calculations. Preliminary low-loss EELS measurements on nanotubes reveal significant differences for the graphite interband transition and collective valence-electron plasmon excitation, which are attributed to the cylindrical structure of the nanotubes.
APPLICATION OF A SINGLE-ACCELERATING TOF METHOD TO COLLISION EXPERIMENTS OF CLUSTER IONS WITH SOLID SURFACES
Authors: KAWADA Y. , SHIROMARU H. , MORIWAKI T. , ACHIBA Y.
Published: October 2004

A time-of-flight mass spectrometer of a non-Wiley-McLaren type, employing a single-acceleration method, was modified for collision experiment of cluster ions with solid surfaces. The intrinsic peak shape in the collision-induced electron-detachment-yield curve was determined by improvement in the energy spread of collided ions. A detailed experimental procedure is presented and the electron-detachment process resulting from low-energy collision is discussed.
DISSOCIATIVE SCATTERING OF SIZE-SELECTED $({\rm{C}}_6 {\rm{F}}_6)_n^-$ (n=1–5) FROM A SILICON SURFACE
Authors: TSUKUDA T. , YASUMATSU H. , SUGAI T. , TERASAKI A. , NAGATA T. , KONDOW T.
Published: October 2004

Scattering processes of a size-selected beam of [Formula: see text](n=1–5) from a silicon surface were investigated using a Tandem time-of-flight (TOF) mass spectrometer. Anionic fragments, F − and [Formula: see text], are produced in the collision of [Formula: see text] at a collision energy in the range of 0–150 eV. The result leads us to conclude that the anionic core of [Formula: see text] is electronically excited upon the surface collision and subsequently dissociates into the fragments. The solvent molecules influence dissociation dynamics of the electronically excited anionic core in low-energy collision.
FRAGMENTATION OF FULLERENES AND METALLOFULLERENES BY SURFACE IMPACT
Authors: BECK R.D. , WEIS P. , ROCKENBERGER J. , MICHEL R. , FUCHS D. , BENZ M. , KAPPES M.M.
Published: October 2004

Fragmentation by surface collision has been studied for the (endohedral) metallofullerene species LaC 82+ and La 2 C 100+. Three different types of fragment ions are detected: (i) Lanthanum-containing carbon clusters formed by loss of C 2 and/or small even-numbered C 2n units, (ii) empty fullerenes [Formula: see text], and (iii) small lanthanum-containing fragments LaC 2n+ with n=0, 1, 2, 3 (and La 2 C 2n, n=1, 2, for La 2 C 100+). Possible fragmentation processes are discussed and the results are compared with the surface-induced fragmentation of higher fullerenes.
ENERGETIC CLUSTER IMPACT (ECI): A NEW METHOD FOR THIN-FILM FORMATION
Authors: HABERLAND HELLMUT , MOSELER MICHAEL , QIANG YOU , RATTUNDE OLIVER , REINERS THOMAS , THURNER YONCA
Published: October 2004

A completely ionized beam of metal clusters is deposited with variable kinetic energy on a substrate. Mirror-like and strongly adhering films having unusual properties are produced for sufficiently high cluster impact energies. Numerical simulations provide the physical insight why this novel technique gives different, and sometimes superior results compared to conventional methods. Several examples are presented.
SOLVATION EFFECTS ON COLLISIONAL PROCESSES OF SIZE-SELECTED ${\rm{I}}_2^- ({\rm{CO}}_2)_n$ CLUSTER IONS WITH SILICON SURFACE
Authors: YASUMATSU HISATO , TSUKUDA TATSUYA , SUGAI TOSHIKI , TERASAKI AKIRA , NAGATA TAKASHI , KONDOW TAMOTSU
Published: October 2004

Collisional processes of [Formula: see text] with a silicon surface were investigated. Size-selected [Formula: see text](n=0–30) were allowed to collide with a silicon surface at collision energies per [Formula: see text] of 1–150 eV at almost normal incidence angles. All the anions scattered from the surface were I −, I −( CO 2), I −( CO 2)2, [Formula: see text], [Formula: see text], and [Formula: see text]. The molecular dynamics simulation revealed that the dissociation of [Formula: see text] occurs through vibrational and rotational excitation. The [Formula: see text] dissociation was found to be either retarded or accelerated by the presence of the solvent CO 2 molecules. The solvation effects on the dissociation of [Formula: see text] were explained in terms of energy transfer between [Formula: see text] and CO 2 solvent molecules and a complex formed on the surface at the moment of the collision.
VIBRATIONAL PROPERTIES AND STRUCTURE OF C60 THIN FILMS ON Si(111)-(7×7) AND GRAPHITE SURFACES
Authors: SUTO SHOZO , KASUYA ATSUO , HU CHANG-WU , WAWRO ANDRZEJ , GOTO TAKENARI , NISHINA YUICHIRO
Published: October 2004

We have investigated the vibrational modes of C 60 thin films adsorbed on the Si (111)-(7×7) and graphite surfaces using high-resolution electron energy-loss spectroscopy in combination with scanning tunneling microscopy (STM). The energy-loss spectra are different in energies and in oscillator strengths for the two surfaces. The differences are attributed to the surface morphology observed with STM. The relation between macroscopic dielectric theory manifested by electron energy loss and microscopic structure measured with STM is discussed in terms of dielectric function theory.
THE STRUCTURAL AND VIBRATIONAL PROPERTIES OF C60 ADSORBED ON THE GRAPHITE(0001) SURFACE
Authors: HUNT M.R.C. , PALMER R.E.
Published: October 2004

The exciting opportunities promised by the unique properties of C60 can only be fully exploited if the growth and properties of this material can be understood. To this end we have carried out a study of the structural and vibrational properties of C60 adsorbed on the graphite(0001) surface. We observed a novel high-order periodicity at monolayer coverages which indicates that even the weak corrugation potential of the surface can perturb the geometry of the overlayer. Vibrational spectra show a low-energy resonance in the inelastic scattering cross section which we correlate with a resonance feature observed in the electron attachment cross section of C60. The lack of a measurable perturbation in the resonance upon going from multilayer to monolayer coverage indicates that a weak physisorption bond exists between the molecules and the surface.
EVOLUTION OF THE ELECTRONIC AND GEOMETRIC STRUCTURES OF SIZE-SELECTED Pt AND Pd CLUSTERS DEPOSITED ON Ag(110) OBSERVED BY PHOTOEMISSION
Authors: ROY H.-V. , PATTHEY F. , FAYET P. , SCHNEIDER W.-D. , DELLEY B.
Published: October 2004

Mass-selected Ptn and Pdn (n=1–15) clusters, generated by ion bombardment, are deposited at room temperature in submonolayer quantities on Ag(110) single-crystal surface and characterized by electron spectroscopy (XPS, UPS). Different sites, reflected in the Pt-5d and Pd-4d binding energies, are observed as a function of the substrate temperature, indicating clearly the surface-subsurface atom exchange processes. The monodispersed clusters indicate individual discrete electronic structure features of the Pt-5d and Pd-4d emission. For the monomers virtual bound-state formation as in dilute (3%) PtAg and PdAg alloys is observed. With increasing cluster size, firstly, the increasing splitting between the bonding-like and antibonding-like d-states reflects the increase in cohesive energy due to molecular interaction, and secondly, the shift of the center of gravity of the d-emission towards the Fermi energy indicates the trend to transition-metal formation.
DYNAMIC ELECTRON MICROSCOPY OF SURFACE DIFFUSION OF TUNGSTEN CLUSTERS ON VACUUM-DEPOSITED MgO SINGLE-CRYSTALLINE FILMS
Authors: TANAKA N. , KIMATA H. , KIZUKA T.
Published: October 2004

The surface-diffusion process of tungsten atoms and clusters on magnesium oxide (001) surfaces is observed directly by high-resolution electron microscopy (HREM) with time resolution of 1/60 sec. It is found from the data reproduced from video-tape images that the diffusion process is classified into a short-jump process to neighboring sites and a long-jump process over a 1-nm distance. The present observation indicates a new potential for the study of the surface-diffusion process with HREM.
FUNDAMENTAL ASPECTS OF THE IONIZED CLUSTER-BEAM DEPOSITION PROCESS
Authors: TAKAOKA G.H. , MATSUO J. , ASCHERON C.E. , YAMADA I.
Published: October 2004

The electron diffraction measurement of Sb beams ejected by adiabatic expansion from a nozzle source showed that a considerable amount of clusters with a highly disordered atomic arrangement was produced. The cluster size was found to be larger than a few tens of atoms per cluster, though the exact size could not be determined. It was reported that after impact of clusters ejected from the nozzle source, cluster islands were formed on a substrate surface, and that the film formation started by direct deposition of clusters as the rapid nucleation of cluster islands. These results supported the notion that large atomic clusters existed in the beam.
FORMATION OF SEMIMAGNETIC SEMICONDUCTOR SUPERLATTICES BY IONIZED CLUSTER-BEAM TECHNIQUE AND THEIR QUANTUM-SIZE EFFECTS
Authors: KOYANAGI T. , OHMOTO H. , MATSUBARA K. , ANNO H.
Published: October 2004

The formation of semimagnetic semiconductor Cd1−xMnxTe superlattices on GaAs (100) and sapphire (0001) substrates by the ionized cluster-beam (ICB) deposition technique and their quantum-size effects on the optical and magneto-optical properties are reported. The observation of high-order satellite x-ray diffraction and the Raman scattering from folded longitudinal acoustic (LA) phonons suggests that the Cd 1−x Mn x Te superlattices have a satisfactory periodic structure. Transitions to the subband levels formed in the wells of superlattices are observed in the optical absorption spectra and the magneto-circular dichroism (MCD) spectra. The transition energies shift widely toward higher energies as the well width is decreased. The experimental results for subband energies agree well with the results calculated using the Kronig-Penney band model. The change in MCD peak height with the well width can be explained in terms of the Zeeman splitting of the subband levels and the oscillator strengths of transitions to those levels.
LSI BARRIER-FILM FORMATION BY IONIZED CLUSTER BEAM
Authors: HASHIMOTO Y. , ISHII H. , TSUKAZAKI H.
Published: October 2004

A simple deposition model of evaporated species into quarter-micron contacts on an 8-inch diameter wafer, considering the scattering by gas molecules, predicted that the narrow angular distribution of evaporated species and deposition under low vacuum pressure are essential conditions for sufficient coverage of the contacts. An ionized cluster-beam (ICB) technique satisfies these essential conditions. The bottom coverage of TiN barrier film deposited by ICB under a nitrogen pressure of less than 10−2 Pa into contacts with an aspect ratio of 4 was improved to about 30% and the bottom coverage uniformity was about ±5% within the wafer. The crystal structure of the film was confirmed to be (111) orientation, which is necessary to form a preferentially oriented aluminum layer with a high durability against electromigration on TiN barrier film.
X-RAY SPECTROSCOPIC ANALYSIS OF BORON-NITRIDE CLUSTERS DEPOSITED BY ION-PLATING METHOD
Authors: KOHZUKI H. , MOTOYAMA M. , KANEYOSHI T. , KOWADA Y. , KAWAI J. , ADACHI H.
Published: October 2004

Cubic boron-nitride (c-BN) films were deposited on a silicon substrate by varying the deposition time, using a reactive ion-plating method. In order to investigate the growth mechanism of c-BN films, these c-BN films were characterized by x-ray emission spectra of boron (B K x-ray emission spectra), infrared absorption spectra, selected area diffraction patterns, and TEM microstructures. It was found that the BN film with sp2 bonding formed initially on the substrate and subsequently c-BN film formed. The c-BN film was composed of fine crystallites with a size of about 10 nm and with random orientation. In the case of the B K x-ray emission spectrum from the BN film with sp 2 bonding, the intensity of the satellite peak at the short-wavelength side was extremely stronger than that of sp 2-bonded BN-like turbostratic or hexagonal BN. As a result of calculation of the B K x-ray emission spectrum of BN using the discrete variational Hartree-Fock-Slater (DV-Xα) method, it was found that the satellite peak intensity increased with formation of the fine BN cluster having two-coordinated boron (which has a dangling bond) and with decreasing size of the cluster. Therefore, it is considered that the BN film with sp 2 bonding was composed of the very fine BN cluster having two-coordinated borons, and became the precursor of c-BN film at the interface between the substrate and c-BN film.
FORMATION AND PROPERTIES OF Ag ULTRAFINE PARTICLES EMBEDDED IN BARIUM OXIDE THIN FILMS
Authors: WU J.L. , ZHANG X. , LIU W.M. , XUE Z.Q. , WU Q.D.
Published: October 2004

A kind of photoemissive thin films, which does not contain alkali elements but contains metallic ultrafine particles, is studied. A typical kind is the thin film of silver ultrafine particles embedded in the barium oxide. There are two methods in the formation of Ag-O-Ba thin films: single-metallic layer method and multimetallic layer method. The photoelectric emission response curve to wavelengths between 350 and 800 nm is given. The energy band with respect to the position diagram in the neighborhood of its surface is also presented. This kind of photoemissive thin films can be exposed or stored in the atmosphere and can be used again in a vacuum system without reactivation process for laser-pulse detection.
OPTICAL PROPERTIES OF CARBON CLUSTERS EMBEDDED IN SiO2 FILMS
Authors: HAYASHI S. , KATAOKA M. , KOSHIDA H. , YAMAMOTO K.
Published: October 2004

Raman spectra were measured for carbon-doped SiO 2 thin films prepared by an rf cosputtering method. The changes in the spectra were systematically studied as a function of the annealing temperature. From a detailed analysis of the spectra, the following conclusions were drawn. In the as-deposited films, very small carbon clusters are embedded in the SiO 2 matrices. When the films are annealed at 600°C, graphite-like sp 2 bonds begin to develop in the clusters. Upon annealing with higher temperatures, the size of sp 2 bond clusters increases. However, the growth of graphite microcrystals can be ruled out, since high-resolution transmission electron microscopic images of the samples annealed at 1000°C do not show lattice fringes due to graphite microcrystals. The samples annealed at 1000°C were found to exhibit an extinction hump around 220 nm, very similar to that seen in the interstellar extinction spectra.
THE CATALYTIC ROLE OF SMALL COINAGE-METAL CLUSTERS IN PHOTOGRAPHY
Authors: LEISNER T. , ROSCHE CH. , WOLF S. , GRANZER F. , WÖSTE L.
Published: October 2004

We model the generation of the photographic latent image in silver-halide systems by the deposition of size-selected silver and gold clusters onto silver-halide microcrystals. Coinage-metal cluster cations were produced in a sputtering arrangement, mass-selected by a quadrupole mass filter, and deposited with a well-controlled kinetic energy onto binderfree silver-bromide crystals. After exposure to the cluster beam, the samples were developed at a defined redox potential. The photographic action of the clusters was investigated as a function of their size, the coverage of the sample with clusters, the kinetic energy of the clusters during the deposition, and the redox potential of the developer. Development was observed after the deposition of [Formula: see text] or larger silver-cluster cations, and under some development conditions, after deposition of [Formula: see text]. No development was observed after the deposition of smaller silver clusters, and after the deposition of gold cluster cations [Formula: see text](n≤9).
QUANTUM CONFINEMENT OF EMBEDDED COPPER CLUSTER SANDWICHED BY LITHIUM FLUORIDE
Authors: WANG G.H. , ZHANG H.Q. , MA J.X. , HAN M. , WANG Q. , ZHAO J.J.
Published: October 2004

Optical absorption and laser Raman scattering spectroscopies as well as EXAFS are used to investigate the copper clusters embedded in the lithium fluoride, and the results indicate that (i) the metal clusters of about 2 nm in diameter have the bulk-like fcc structure with a contracted interatomic distance and lower mean coordination number, (ii) the embedded metal clusters show a surface-plasmon resonance, (iii) for clusters smaller than certain size the surface-phonon mode becomes important, and the high-order longitudinal phonon vibrational modes emerge.
OPTICAL SPECTROSCOPY OF SIZE-SELECTED SILVER CLUSTERS EMBEDDED IN SOLID NEON: A CLUSTER-SUPPORT INTERACTION STUDY
Authors: HARBICH W. , BELYAEV Y. , KLEIBER R. , BUTTET J.
Published: October 2004

Silver ions comprising 8, 11, 20, and 21 atoms have been produced by sputtering, mass-selected in a quadrupole mass filter and deposited at 30-eV landing energy together with neon on a 5-K sapphire support. The absorption spectra show results similar to the system Ag n / argon , but are better resolved. The spectra are compared to gas-phase depletion data and to corresponding sodium clusters. The matrix shift is analyzed and a value of the gas-phase position of the spectra is given.
DEFECTS OF A15 SMALL PARTICLES IN TUNGSTEN THIN FILMS
Authors: ARITA MASASHI , NISHIDA ISAO
Published: October 2004

Crystal defects of A15 small particles in tungsten thin films were studied by means of transmission electron microscopy. Defects found in nanoscale crystals were analyzed to have special structure containing the Zr4Al3-type structure unit.
FORMATION STEPS OF CdS CLUSTERS IN AQUEOUS SOLUTION CONTAINING 2-MERCAPTOETHANOL
Authors: NOSAKA YOSHIO , SHIGENO HARUO , IKEUCHI TOMOMI
Published: October 2004

Growing steps of CdS clusters in aqueous solution containing HOCH 2CH2 SH (2-mercaptoethanol, RSH) was investigated by means of stopped flow optical spectroscopy and proton NMR spectroscopy. When the amount of RS − was 4 times larger than Cd 2+ ions at alkaline pH, the growing cluster showed the change in the absorption peak via 242, 260, 280, 308, and 315 nm. Initial three peaks were assigned to [ Cd 1( SR )4]2−, [ S 1 Cd 4(SR)12]6−, and [ S 1 Cd 8( SR )16]2−, respectively. Among them, the cluster at 280 nm was very stable, comparable with the reported thiophenolate cluster [ S 1 Cd 8( SPh )16]2−. The relationship between the size and the absorption maximum for ultrasmall CdS particles reported was continuous to that obtained for the clusters in the present study.
SYNTHESIZED “IN SITU” IN REVERSE MICELLES OF SILVER-SULFIDE SEMICONDUCTORS
Authors: PILENI M.P. , MOTTE L. , BILLOUDET F. , PETIT C.
Published: October 2004

Functionalized reverse micelles are used to control the size of silver sulfide, Ag 2 S , nanosize particles. The size of the crystallites varies linearly with the water content from 2 to 10 nm. The particles have been coated with dodecanethiol and extracted from micelles. The size of the particles dispersed in heptane has been determined by small-angles x-ray scattering (SAXS) experiments and compared to those obtained by transmission electron microscopy (TEM). A good agreement between results is obtained by these two techniques. A drop of particles previously dispersed in heptane is dried on a carbon grill. A network of the particles forming monolayers of crystallites in a hexagonal distribution appears.
RATE PROCESS OF THE COAGULATION OF NANOPARTICLES
Authors: KIMURA K.
Published: October 2004

Nanometer-sized gold particles dispersed in organic liquids coagulate under the influence of addition of salt or illumination of Mie resonance irradiation. It is derived that the van der Waals attractive force can be enhanced by the excitation of surface plasmon, hence the rate of coagulation is accelerated through the DLVO (Derjaguin, Landau, Verway, Overbeek) potential among the particles. The coagulation rate and the stability ratio are calculated within a framework of DLVO theory.
THERMAL BEHAVIOR OF THE CLEAN Ni(111) SURFACE
Authors: GUSEV E.P. , LU H.C. , GARFUNKEL E. , GUSTAFSSON T.
Published: October 2004

High resolution medium energy ion scattering has been used to study the interlayer spacing and atomic vibrations at the Ni(111) surface in the temperature range of 430–1100 K. The surface was not found to exhibit significant relaxation; it remains nearly bulk-terminated for all temperatures studied. The amplitudes of the atomic vibrations at T <800 K are enhanced by 30–40% with respect to their bulk values. This enhancement increases drastically at higher temperatures, so that the surface amplitudes become twice as large as the bulk amplitudes at 1100 K. We did not observe changes in the surface-structural properties near the Curie point.
SURFACE STRUCTURES AND GROWTH MODES FOR Cu ON Si(100), (110) AND (111) SURFACES DEPENDING ON Cu SEGREGATION BY HEAT TREATMENT
Authors: IKEDA T. , WATANABE T. , ITOH H. , ICHINOKAWA T.
Published: October 2004

Cu has a large diffusion coefficient in Si, like Ni, and hence the deposited Cu atoms on the Si clean surfaces diffuse into the bulk with increasing temperature and segregate to the surface by quenching. Thus, the surface reconstructed structure changes by heat treatment depending on the surface Cu concentration induced by heat treatment. Moreover, the quantity of Cu segregation decreases with increasing annealing time, because the diffused Cu atoms are trapped to islands on the surface while annealing. The quantity of diffusing Cu atoms into the bulk and the desorption temperatures of Cu from the reconstructed surfaces depend on the crystallographic orientations of the substrate surface. Different cohesive energies of the surface superstructures and different temperatures of the Cu segregation depending on surface orientations are discussed based on the structures on Cu–Si layers formed on the Si (100), (110) and (111) surfaces.
EVOLUTION OF LATERAL ORDER AND MOLECULAR REORIENTATION IN THE BENZOATE/Cu(110) SYSTEM
Authors: FREDERICK B.G. , LEIBSLE F.M. , HAQ S. , RICHARDSON N.V.
Published: October 2004

Coverage-dependent adsorption studies of benzoic acid on a Cu(110) single crystal surface resulted in a sequence of novel, large periodicity structures containing differently oriented benzoate species, as shown by LEED, STM and FTIR. At low coverage, only flat-lying benzoate species are present and faceting of step edges is observed. The favorable mobility of flat-lying species results in formation of large, single domain islands with a [Formula: see text] periodicity containing four molecules per unit cell. Additional adsorption produces island growth, with single domains typically covering entire terraces and, simultaneously, addition of a fifth benzoate species per unit cell oriented perpendicular to the surface. This structure, denoted as the “α phase,” corresponds to a local coverage of θ=0.21 ML. Then, the periodicity changes to a [Formula: see text] structure with single and paired rows of upright species, retaining the dominant <4, 3> direction and large single domain sizes, in addition to six flat-lying species. The second structure, referred to as the “β phase,” corresponds to a local coverage of θ= 0.23 ML. The saturation coverage, c(8×2) structure, at θ=0.25 ML, grows in from step edges and contains only upright benzoate species. The results are interpreted in terms of the interplay between molecular orientation, site-specificity, diffusion and the intermolecular interactions favoring long range, two-dimensional order.
IMAGE STATES OF Ag ON Au(111)
Authors: REUß C. , WALLAUER W. , FAUSTER TH.
Published: October 2004

The image states for thin Ag layers on Au(111) have been studied with two-photon photoemission. The energies of the states show the behavior characteristic for a layer-by-layer growth of large terraces with their characteristic local work function. Image states with rather large linewidths are observed at energies outside the band gap of the projected bulk band structure. The identification of the states is complicated by the dominating signal from the occupied surface state.
THERMAL DESORPTION ACCOMPANIED BY DECOMPOSITION OF ADSORBED MOLECULES
Authors: Zhdanov V.P.
Published: October 2004

The effect of adsorbate–adsorbate lateral interactions on TPD spectra is analyzed in the case where the desorption process is accompanied by decomposition of molecules remaining on the surface. General results are used to interpret the kinetics of NO desorption from Rh(111).
STRUCTURAL STUDIES OF OXIDE SURFACES
Authors: GUSTAFSSON T. , GARFUNKEL E. , GUSEV E.P. , HÄBERLE P. , LU H.C. , ZHOU J.B.
Published: October 2004

We review some recent ion scattering experiments on the structure of oxide surfaces. We show that the MgO(100) surface exhibits very small surface distortions, in agreement with recent theoretical work. For the case of the oxidation of Si(100), we show that the oxidation proceeds in three different spatially separate regions, something which disagrees with the conventional model for silicon oxidation.
DENSITY FUNCTIONAL THEORY STUDY OF Na ON Al(111) AND O ON Ru(0001)
Authors: STAMPFL C.
Published: October 2004

The success of density functional theory for the description of the adsorption of atoms on surfaces is well established and, based on recent calculations using gradient corrections, it has been shown that it also describes well the dissociative adsorption of molecules at surfaces — admittedly, however, the database for reactions at surfaces is still somewhat small. In this paper the power of density functional theory calculations is demonstrated through investigations for two different adsorption systems, namely one with a strongly electropositive adsorbate [Na on Al(111)] and one with a strongly electronegative adsorbate [O on Ru(0001)]. In each case, new hitherto unexpected adsorbate phases have been predicted by the theory: for Na on Al(111) the stability of a “four-layer” surface alloy was identified while for O on Ru(0001) it was predicted that the formation of a (1×1)-O adlayer should be possible which implies that the apparent saturation coverage of Θo=1/2 is due to kinetic hindering.
TENSOR LEED FOR THE GEOMETRICAL AND CHEMICAL STRUCTURE OF ALLOY SURFACES
Authors: HEINZ K. , DÖLL R. , KOTTCKE M.
Published: October 2004

Low energy electron diffraction is still the most frequently used technique to retrieve the structure of surfaces. Multiple scattering of electrons on the one hand provides high structural precision but on the other hand also complicates the structural analysis and limits the complexity of accessible structures. This particularly applies to alloy surfaces with their enlarged variety of possible structures which comes by the increased size of the surface unit cell (chemically ordered alloys) or the unknown layer-dependent stoichiometry (disordered alloys). A way out of that dilemma comes by application and further development of the perturbation method Tensor LEED. We show that it can be extended to treat efficiently and accurately the chemical substitution of atoms. This allows easy access to the layer-dependent stoichiometry of chemically disordered alloys. Also, by periodic substitution of atoms, intensities calculated for an elemental crystal can be perturbed to yield the intensities for an ordered alloy. Moreover, we propose and test the application of a direct method which gives the deviations from bulk stoichiometry directly, i.e. without the usual trial and error procedure.
ADSORBATE-INDUCED VARIATION OF THE STRUCTURE AND COMPOSITION OF THE Mo0.75Re0.25(100) SURFACE
Authors: HAMMER L. , KOTTCKE M. , HEINZ K. , MÜLLER K. , ZEHNER D. M.
Published: October 2004

Clean random alloy surfaces usually exhibit non-bulklike concentration profiles. Adsorption at low temperatures does not modify these profiles as there is thermal activation for interdiffusion of surface atoms required. For strongly chemisorbed species like oxygen or carbon, however, the activation barrier can be overcome prior to desorption leading to a new equilibrium distribution of the surface constituents. This paper summarizes the results of different LEED-I(V) studies on the adsorption of hydrogen, oxygen and carbon on the (100) face of the random alloy Mo 0.75 Re 0.25. Hydrogen, which desorbs near room temperature, is found to affect the interlayer spacings only, whilst the concentration profile remains completely unchanged. In contrast, enhanced molybdenum segregation at temperatures above 600° C is shown to happen with oxygen and carbon adsorption leading to exclusive Mo-C and Mo-O bonds, respectively. The surface structures formed for high coverages differ substantially from each other. Oxygen induces a missing row structure and is bound in a “quasi” three-fold coordinated site. In contrast, carbon is adsorbed in five-fold hollow sites at the surface and in six-fold coordinated octahedral subsurface sites.
BULK AND SURFACE ELECTRONIC STATES OF ORDERED Cu3Au(001): AN ANGLE-RESOLVED PHOTOEMISSION INVESTIGATION
Authors: LÖBUS S. , COURTHS R. , HALILOV S. , GOLLISCH H. , FEDER R.
Published: October 2004

We have performed an angle-resolved ultraviolet photoemission spectroscopy (ARUPS) investigation of ordered Cu 3Au(001) at room temperature using He resonance and synchrotron radiation. The positions of upper Cu -like bulk bands near the center Γ of the bulk Brillouin zone (BZ) and the dispersion of the upper sp band along the A line have been determined using bulk-sensitive photon energies 10 eV≤hν≥15 eV. Except for a downward shift, the calculated bulk bands are in excellent agreement with experiment. Around the centers [Formula: see text] of the surface BZ, we have identified three new surface states in the energy region of the Au-like states and several surface-sensitive features in the Cu -like region below the known surface state on top of the Cu-like bulk d bands. These states strongly contribute to the ARUPS spectra for hν≥20 eV. The wealth of surface features found is in overall agreement with a recent surface electronic structure calculation [S. Halilov, H. Gollisch, E. Tamura and R. Feder, J. Phys.: Condens. Matter5, 4711 (1993)]. More detailed information is obtained by comparing the experimental spectra with theoretical ones calculated by a relativistic one-step model formalism.
THE PHYSICAL AND ELECTRONIC STRUCTURE OF THE Cu85Pd15(110) SURFACE: CLUES FROM THE STUDY OF BULK CuxPd1−x ALLOYS
Authors: COLE R. J. , BROOKS N. J. , WEIGHTMAN P. , FRANCIS S. M. , BOWKER M.
Published: October 2004

The (110) surface of Cu 85 Pd 15 adopts an ordered structure which can be controlled by Ar bombardment and thermal treatment. A summary is given of the large body of theoretical and experimental work on the physical and electronic structure of bulk Cu x Pd 1−x alloys. The electronic structure of the ordered Cu 85 Pd 15(110) surface is discussed in terms of the conclusions drawn from the study of bulk CuPd alloys.
SURFACE EFFECTS IN RARE-EARTH MATERIALS
Authors: LAUBSCHAT C. , WESCHKE E.
Published: October 2004

Recent experimental results concerning the surface-related electronic structure of rare-earth (RE) compounds are presented. Special attention is paid to the occurrence of surface-valence transitions for trivalent and mixed-valent compounds of Sm, Eu, Tm and Yb which are due to an energetical lowering of unoccupied 4f states caused by the reduced atomic coordination at the surface. Similar phenomena are observed for so-called α-like Ce compounds which are characterized by a strong hybridization of the 4f levels with valence-band states. Here, the reduced atomic coordination causes mainly a decrease in hybridization leading to an enhanced localization of the 4f states in the outermost atomic surface layer. The importance of this phenomenon for the correct interpretation of electron-spectroscopic data of Ce systems is discussed.
SEGREGATION PHENOMENA ON PtxNi1−x LOW INDEX SINGLE CRYSTAL SURFACES STUDIED BY STM
Authors: VARGA P. , SCHMID M. , HOFER W.
Published: October 2004

Surface segregation changes the composition of alloy surfaces. It influences both the geometrical and the chemical structure of the surface. In this paper segregation phenomena are shown for low index single crystal surfaces of different PtNi alloys which can be seen only by scanning tunneling microscopy (STM).

STM experiments performed with atomic resolution revealed the existence of subsurface dislocation networks. A closer study of the conditions of their existence allowed us to understand the effects of preferential sputtering and annealing on the segregation behavior (i.e. building up a rather stable altered layer and its disappearance only at elevated temperatures). In addition, local chemical ordering in small domains and shifted row reconstructions with a large and varying periodicity (i.e. phenomena that are hardly seen by other methods like e.g. LEED) have been observed.
ADSORPTION ON ORDERED BINARY ALLOY SURFACES: HYDROGEN ADSORPTION ON THE CLEAN AND CO-COVERED Cu3Pt(111) SURFACE
Authors: BECKER C. , SCHRÖDER U. , LINKE R. , SCHIEFFER B. , WANDELT K.
Published: October 2004

The adsorption of hydrogen, as well as the interaction of adsorbed CO and hydrogen, on the Cu 3 Pt (111) surface have been studied using thermal desorption spectroscopy (TDS), high resolution electron energy loss spectroscopy (HREELS) and work function change measurements (ΔΦ). The results show that hydrogen adsorption and dissociation occur via platinum sites. The process proceeds with second order kinetics with respect to the number of platinum sites available. The desorption spectra are successfully simulated using a lattice gas model. From the simulations the desorption and lateral interaction energies are deduced, showing a weak hydrogen-hydrogen repulsion. The interaction of coadsorbed CO and hydrogen has also been investigated. In contrast to the Pt(111) surface where a lateral segregation of the two adsorbed species takes place, the results presented here suggest a mixed overlayer.
CLEAN AND OXYGEN-COVERED Cu3Au(110): A SURFACE STRUCTURE INVESTIGATION WITH STM AND NICISS
Authors: NIEHUS HORST , BAUMANN THOMAS , VOETZ MATTHIAS , MORGENSTERN KARINA
Published: October 2004

Cu 3 Au (110) has been investigated by scanning tunneling microscopy (STM) and 180° low energy ion scattering and detection of neutrals (NICISS). Two different terminations would be possible on the basis of a bulk-truncated surface, a gold-rich or a pure copper surface layer. From the NICISS investigation the gold-rich termination has been found. Two surface modifications could be prepared. Rapid cool-down after annealing at 800 K results in a 2×1 LEED superstructure, but careful preparation and prolonged cooling below 600 K gives a LEED 4×1 superstructure. A new pairing row model has been proposed. Upon oxygen exposure at 330 K on the quenched 2×1 surface and subsequent annealing at 800 K, a 2×1 LEED superstructure presents itself with considerably sharper half order reflexes. NICISS data propose a segregation of Cu atoms to the surface layer forming -Cu-O- rows just above the Cu rows in the Au -rich layer. The 2×1 superstructure formed is in part similar to the well-known added row structure at Cu (110)-(2×1)-O. The structure model has been verified by direct imaging of the added rows with STM.
THE ADSORPTION OF OXYGEN ON Hong NiAl(001) AT 300 K AND 20 K
Authors: FRANCHY R. , SO S. K. , GAßMANN P.
Published: October 2004

The adsorption of oxygen on NiAl at 300 K and 20 K has been studied by means of high resolution electron energy loss spectroscopy (EELS), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The adsorption of oxygen at 300 K leads to formation of a thin film of amorphous aluminum oxide ( a-Al 2 O 3). After oxygen adsorption at 300 K and annealing of the oxygen-saturated surface to 1200 K, a well-ordered thin θ-Al2O3 film is formed. After annealing of the oxygen-saturated surface to 1400 K, an α-like Al 2O3 oxide is grown. Even at 20 K oxidation of the NiAl (001) surface is found. However, at higher exposure (≥ 5 L) oxygen physisorbs and the EEL spectrum exhibits characteristics of resonance scattering. The resonance energy for physisorbed oxygen on the amorphous Al oxide layers formed at 20 K has a value of 7.0 eV. The frequency of O-O stretching vibration for physisorbed O2 is 193 meV. The line shape of this mode is asymmetric with a pronounced tail on the high energy side. The asymmetric line shape corresponds to multiple losses due to the overlap of the O-O stretching mode with low frequency modes. After physisorption of oxygen at 20 K on the α-like Al oxide layers, the resonance energy is shifted to 9.0 eV, a value close to that of oxygen in the gas phase.
STATISTICAL DYNAMICS IN PIECEWISE LINEAR COURNOT GAME WITH HETEROGENEOUS DUOPOLISTS
Authors: MATSUMOTO AKIO
Published: October 2004

We study a Cournot duopoly dynamic model in which reaction functions are piecewise linear. Such a model typically generates ergodic chaos when it involves strong nonlinearites. To investigate statistical properties, we construct explicit forms of density functions associated with chaotic trajectories. We demonstrate that the long-run average behavior possesses regular properties although each chaotic trajectory exhibits irregular motions. In particular, the ratios of the average outputs and the average profits are the same as those of Cournot outputs and Cournot profits.
SYMMETRIES IN CLASSICAL FIELD THEORY
Authors: DE LEÓN MANUEL , MARTÍN DE DIEGO DAVID , SANTAMARÍA-MERINO AITOR
Published: October 2004

The multisymplectic description of Classical Field Theories is revisited, including its relation with the presymplectic formalism on the space of Cauchy data. Both descriptions allow us to give a complete scheme of classification of infinitesimal symmetries, and to obtain the corresponding conservation laws.
THE DIRAC MONOPOLE AND DIFFERENTIAL CHARACTERS
Authors: KALOGEROPOULOS NIKOS
Published: October 2004

We describe the Dirac monopole using the Cheeger–Simons differential characters. We comment on the role of the Dirac string and on the connection with Deligne cohomology.
NONTRIVIAL CLASSES IN H*(Imb(S1,ℝn)) FROM NONTRIVALENT GRAPH COCYCLES
Authors: LONGONI RICCARDO
Published: October 2004

We construct nontrivial cohomology classes of the space Imb (S1,ℝn) of imbeddings of the circle into ℝn by means of Feynman diagrams. More precisely, starting from a suitable linear combination of nontrivalent diagrams, we construct, for every even number n≥4, a de Rham cohomology class on Imb (S1,ℝn). We prove nontriviality of these classes by evaluation on the dual cycles.
Polymorphic specialization for ML
Authors: Helsen Simon , Thiemann Peter
Published: October 2004

We present a framework for offline partial evaluation for call-by-value functional programming languages with an ML-style typing discipline. This includes a binding-time analysis which is (1) polymorphic with respect to binding times; (2) allows the use of polymorphic recursion with respect to binding times; (3) is applicable to a polymorphically typed term; and (4) is proven correct with respect to a novel small-step specialization semantics.The main innovation is to build the analysis on top of the region calculus of Tofte and Talpin [1994], thus leveraging the tools and techniques developed for it. Our approach factorizes the binding-time analysis into region inference and a subsequent constraint analysis. The key insight underlying our framework is to consider binding times as properties of regions.Specialization is specified as a small-step semantics, building on previous work on syntactic-type soundness results for the region calculus. Using similar syntactic proof techniques, we prove soundness of the binding-time analysis with respect to the specializer. In addition, we prove that specialization preserves the call-by-value semantics of the region calculus by showing that the reductions of the specializer are contextual equivalences in the region calculus.
Symmetry and reduced symmetry in model checking
Authors: Sistla A. Prasad , Godefroid Patrice
Published: October 2004

Symmetry reduction methods exploit symmetry in a system in order to efficiently verify its temporal properties. Two problems may prevent the use of symmetry reduction in practice: (1) the property to be checked may distinguish symmetric states and hence not be preserved by the symmetry, and (2) the system may exhibit little or no symmetry. In this article, we present a general framework that addresses both of these problems. We introduce "Guarded Annotated Quotient Structures" for compactly representing the state space of systems even when those are asymmetric. We then present algorithms for checking any temporal property on such representations, including non-symmetric properties.
Voice says it all in the Navy
Authors: Paper David J. , Rodger James A. , Simon Steven J.
Published: October 2004

The commercial potential for voice technology innovations currently being developed by the U.S. Navy is immense.
A science of design for software-intensive systems
Authors: Freeman Peter , Hart David
Published: October 2004

Computer science and engineering needs an intellectually rigorous, analytical, teachable design process to ensure development of systems we all can live with.
Physically based virtual painting
Authors: Lin Ming , Baxter William , Scheib Vincent , Wendt Jeremy
Published: October 2004

Tapping the compelling illusion of physical interaction with paints, brushes, surfaces, color, and light, users express the nuances of their visual and emotional imaginations.
Adaptive document layout
Authors: Jacobs Charles , Li Wil , Schrier Evan , Bargeron David , Salesin David
Published: October 2004

How to automatically reformat, resize, and paginate electronic text and graphics so documents look as good on displays of any size as they do on paper.
Cluster communication protocols for parallel-programming systems
Authors: Verstoep Kees , Bhoedjang Raoul A. F. , Rühl Tim , Bal Henri E. , Hofman Rutger F. H.
Published: October 2004

Clusters of workstations are a popular platform for high-performance computing. For many parallel applications, efficient use of a fast interconnection network is essential for good performance. Several modern System Area Networks include programmable network interfaces that can be tailored to perform protocol tasks that otherwise would need to be done by the host processors. Finding the right trade-off between protocol processing at the host and the network interface is difficult in general. In this work, we systematically evaluate the performance of different implementations of a single, user-level communication interface. The implementations make different architectural assumptions about the reliability of the network and the capabilities of the network interface. The implementations differ accordingly in their division of protocol tasks between host software, network-interface firmware, and network hardware. Also, we investigate the effects of alternative data-transfer methods and multicast implementations, and we evaluate the influence of packet size. Using microbenchmarks, parallel-programming systems, and parallel applications, we assess the performance of the different implementations at multiple levels. We use two hardware platforms with different performance characteristics to validate our conclusions. We show how moving protocol tasks to a relatively slow network interface can yield both performance advantages and disadvantages, depending on specific characteristics of the application and the underlying parallel-programming system.
Why is software always late?
Authors: Lawrence J. L.
Published: October 2004

Despite all of the advances in software engineering practice, despite all the newly developed languages and software tools, and despite case study after case study, software is almost always late. It does not seem to matter what the product is or what the industry is. The cry of frustration is almost always the same: "Why is software always late?" In this article, the author discusses the software development cycle and the LOC/day productivity measure in an attempt to explore some of the reasons for failure and some of the factors contributing to success. The opinions expressed herein are soley those of the author and do not necessarily reflect views or procedures of the General Electric Company or its employees.