bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of the radiation doses occurring in the human body for inadvertent ingestion of soil and other soil exposure pathways
Authors: Öner F , Okumuşoğlu N T
Published: December 2003

We estimate the radiation doses in the human body, in the Gudalore region in India, following the inadvertent ingestion of soil and exposure to other soil pathways by measuring 232Th, 238U, and 40K. We estimate the equivalent dose in eleven different organs and the absorbed dose calculations for the whole body. The annual effective doses are calculated, the lowest is in Kariyasolai at 7.8 × 103 mSv whereas the highest is in Ponnur at 8.9 × 102 mSv. In all regions, the lowest equivalent doses through inadvertent soil ingestion are calculated in the kidney and thyroid whereas the highest doses are in the red marrow and on the bone surface. PACS No.: 87.50.a
Superspace models for S3
Authors: McKeon D.G.C.
Published: December 2003

The simplest supersymmetric extension of the group SO(4) is discussed. The superalgebra is realized in a superspace whose Bosonic subspace is the surface of a sphere S3 embedded in four-dimensional Euclidean space. By using Fermionic coordinates in this superspace, which are chiral symplectic Majorana spinors, it proves possible to devise superfield models involving a complex scalar, a pair of chiral symplectic Majorana spinors, and a complex auxiliary scalar. Kinetic terms involve operators that are isometry generators on S3.PACS No.: 11.30.Pb
Influence de la température de substrat sur la croissance et les propriétés des films minces de silicium amorphe déposés par pulvérisation cathodique
Authors: Abdesselem S , Ouhab A , Aida M S
Published: December 2003

We deposit thin films of a-Si:H by RF diode spray on substrate with temperatures varying from 200 to 500 °C. Knowing that this deposition method is violent when compared with the plasma-assisted deposition method, we have used low RF power to limit the energy of the Ar ions bombarding the surface of the growing film. Characterization of the films by UVvisible absorption spectroscopy suggests that the influence of the substrate temperature can be classified into three different regimes: (i) low temperature, Ts < 300 °C: the films show a strong disorder, the hydrogen is bound only in the polyhydric configuration; (ii) intermediate temperature, 300 °C < Ts < 400 °C: film growth is rapid, the films present a lower defect density; this may be the best regime to make good quality a-Si:H films using the spraying method; (iii) high temperature, Ts > 400 °C: the films are more organized, but less hydrogenated. The substrate temperature influences the film properties by modifying the growing mechanism through a control of the reactions taking place at the plasmasubstrate interface, where the hydrogen dynamics play a fundamental role.[Journal translation]
ORDERING AT SURFACES FROM ELASTIC AND ELECTROSTATIC INTERACTIONS
Authors: VANDERBILT DAVID
Published: December 2003

Elastic and electrostatic interactions can sometimes have a profound influence on surface morphology. Here, we review the conditions under which surface stress or surface dipole variations can give rise to spontaneous domain formation at surfaces, and focus especially on the case of the Si(100) surface. In principle, the anisotropy of the surface stress should cause the spontaneous formation of a striped domain structure on Si(100). In practice, the length scale for this domain structure turns out to be so large as to prevent its direct observation, although the influence of the elastic interactions has been observed indirectly in a variety of related experiments. It is now evident that by introducing Ge or B atoms, the conditions can be tuned in such a way that the spontaneous domain formation is strikingly observed. Because surface electrostatic dipolar interactions scale in the same way as elastic ones, it follows that similar effects can arise from these sources. We consider a simple model two-phase surface system with 1/r3 dipolar interactions, and find that the model exhibits spontaneous formation of two kinds of periodic domain structure. A striped domain structure is stable near half-filling, but as the area fraction is changed, a transition to a hexagonal lattice of almost-circular droplets occurs. The relation of this model to experimental surface systems, especially that of Langmuir layers at the water–air interface, will be discussed.
THE IMPORTANCE OF STRAIN ANALYSIS IN STUDIES OF PSEUDOMORPHIC GROWTH
Authors: JONA F. , MARCUS P. M.
Published: December 2003

Since a pseudomorphic film is usually strained both in the plane of the surface and in the perpendicular direction, strain analysis is necessary in order to determine the strains and identify the equilibrium (i.e. the unstrained) phase of the film material. A procedure for carrying out the strain analysis within the limits of linear elasticity theory is described by way of a simple hypothetical example with cubic {001} surfaces, which illustrates the concept of epitaxial lines. These are lines relating the perpendicular spacing between atomic planes, as produced by epitaxial strain on a stable or metastable crystal phase, to the in-plane spacing in pseudomorphic films.
ALLOY SURFACE STRUCTURE: COMPUTER SIMULATIONS USING THE BFS METHOD
Authors: BOZZOLO GUILLERMO , FERRANTE JOHN
Published: December 2003

The use of semiempirical methods for modeling alloy properties has proven to be difficult and limited. The two primary approaches to this modeling, the embedded atom method and the phenomenological method of Miedema, have serious limitations in the range of materials studied and the degree of success in predicting properties of such systems. Recently, a new method has been developed by Bozzolo, Ferrante and Smith (BFS) which has had considerable success in predicting a wide range of alloy properties. In this work, we reference previous BFS applications to surface alloy formation and alloy surface structure, leading to the analysis of binary and ternary Ni-based alloy surfaces. We present Monte Carlo simulation results of thin films of NiAl and Ni–Al–Ti alloys, for a wide range of concentration of the Ti alloying addition. The composition of planes close to the surface as well as bulk features are discussed.
SHAPE INSTABILITIES NEAR fcc(110) MISSING-ROW RECONSTRUCTED FACETS
Authors: CARLON ENRICO , VAN BEIJEREN HENK
Published: December 2003

In STM experiments certain vicinal orientations of missing-row reconstructed (110) facets have been found to be covered by a network of crossing steps. We introduce a simple model to study these networks, which predicts shape instabilities for a range of vicinal orientations. We show some resulting equilibrium facet shapes as well as the global structure of the surrounding regions.
THE MICROSCOPIC ORIGIN OF NONMELTING AND SURFACE OVERHEATING AT CLOSE-PACKED METAL SURFACES
Authors: ERCOLESSI FURIO , DI TOLLA FRANCESCO D. , TOSATTI ERIO
Published: December 2003

We review recent work done in our group on the high-temperature behavior of metal surfaces. In particular, the nonmelting behavior of many close-packed metal surfaces, and their ability to sustain overheating, are discussed in connection with an effective attraction between the solid–liquid and the liquid–vapor interfaces, due to strong surface layering. This also implies partial wetting of the solid surface by the melt.
LONG-RANGE ORIENTATIONAL CORRELATIONS AT UNDERCOOLED LIQUID METAL SURFACES
Authors: CELESTINI FRANCK , ERCOLESSI FURIO , TOSATTI ERIO
Published: December 2003

The liquid surface of a reconstructing metal such as Au or Pt is expected to exhibit a higher surface lateral density as compared to an equivalent slice of bulk liquid. Using a realistic potential and molecular dynamics, we have analyzed the surface behavior of liquid gold as a function of temperature. The density profile along the surface normal develops, as a consequence, marked layering oscillations, while surface atoms are forced to a nearly triangular lateral packing. The undercooled surface, in particular, reveals the onset of very long-range sixfold orientational correlation [Formula: see text]. At the same time positional correlations do not vary appreciably. The growth of ξ6 upon cooling is dramatic near 1000 K, and the liquid metal surface appears to approach a transition into a hexatic phase at about 940 K. This temperature is, however, inaccessible to simulation, due to surface-initiated recrystallization on the nanosecond time scale.
PREROUGHENING, AND DISORDERED FLAT PHASE SEPARATION IN SURFACE MOLECULAR DYNAMICS SIMULATIONS
Authors: PRESTIPINO SANTI , JAYANTHI C. S. , ERCOLESSI FURIO , TOSATTI ERIO
Published: December 2003

Ordinary molecular dynamics surface simulations are particle-conserving. We have found that, while this restriction may be adequate for a majority of situations, there exists for most surfaces a range of temperatures where that is not the case. The critical temperature range is between preroughening and roughening. There, the surface equilibrium state is disordered and flat (DOF), implying a state of roughly half-filling for the outermost surface layer. A particle-conserving simulation, based initially on a well-defined, usually integer, number of crystalline layers, must phase-separate into two half-layered domains. We discuss evidence, indicating that this kind of phase separation is actually taking place in existing simulations.
OVERDAMPED DIFFUSION IN COUPLED POTENTIALS
Authors: CARATTI G. , FERRANDO R. , SPADACINI R. , TOMMEI G. E.
Published: December 2003

An analytical "quasi-2D" approximation (Q2DA) for the diffusion coefficient of an adatom migrating in a rectangular lattice, in the presence of a high damping and of a general 2D-coupled potential, is derived. The validity of the Q2DA lies on the assumption that all the most relevant diffusion paths can be treated as straight lines. That is the case of the square 2D-coupled egg-carton potential, where the Q2DA is applied. Comparison with the exact numerical results (2D Smoluchowski equation) shows that the Q2DA provides a very good approximation of the diffusion constant even in the strongest coupling situations.
MICROSCOPIC THEORY AND SIMULATION OF ADATOM DIFFUSION ON Ir(111)
Authors: OUANNASSER S. , HABAR M. , STAUFFER L. , DREYSSÉ H. , WILLE L. T.
Published: December 2003

Using a realistic tight-binding Hamiltonian we have calculated the effective cluster interactions that describe the ordering of adsorbed Ir atoms on the Ir (111) surface. We have determined the relative stability of adatoms in "bulk" and "surface" sites and also mapped out the barrier between them. This information is then used as input in Monte Carlo simulations which allow us to determine typical diffusion behavior at various temperatures.
MOLECULAR SIMULATION OF PLATINUM CLUSTERS ON GRAPHITE
Authors: WU GUANG-WEN , CHAN KWONG-YU
Published: December 2003

Molecular dynamics calculations of platinum atoms on a graphite surface are performed with different coverages of platinum to simulate the deposition and cluster formation process. The Sutton–Chen many-body potential is used for the Pt–Pt interaction whereas a Steele potential with energy minima representing adsorption sites is used to represent the carbon surface. The cluster size distribution, structure of clusters, effect of loadings, migration, and oxygen adsorption effects are investigated.
SURFACE ROTATIONAL DISORDERING IN CRYSTALLINE C60
Authors: PASSERONE D. , TOSATTI E.
Published: December 2003

We present a theory of surface rotational disordering of crystalline fullerene. Realistic intermolecular interactions are implemented, in a layer-by-layer mean field theory. The crucial new ingredient turns out to be a one-body potential energy term, or "crystal field," is totally different at the surface, therefore locally frustrating bulk order. This frustration causes a severe surface order parameter reduction, and a first order surface rotational disordering transition, well below the corresponding bulk one. Preliminary results are in agreement with recent experiments, confirming a first order surface rotational transition of C 60(111) at a transition temperature lower than the bulk one.
ANISOTROPY OF TRANSLATIONAL DIFFUSION IN PREMELTED METHANE FILMS
Authors: STOCKER P. , GAY J.-M. , BIENFAIT M. , CODDENS G.
Published: December 2003

Surface melting of the (111) face of methane films adsorbed on graphite is investigated by quasielastic neutron scattering with special attention paid to translational diffusion within the liquid-like layer parallel and normal to the surface. The comparison of the experimental spectra measured in different geometries clearly shows diffusion anisotropy. Simulations of the data provide an estimation of the anisotropy as a function of temperature.
MONTE-CARLO SIMULATION OF MBE GROWTH OF GaAs ANALYSIS OF RHEED
Authors: VAN HALL P. J. , KÖKTEN H. , LEYS M. R. , BOSCH M.
Published: December 2003

We have performed Monte-Carlo simulations of the growth of GaAs by MBE. We included in our calculations the anisotropy of the migration, the formation of As-and a partial desorption of the As. As an observable we calculated the RHEED signal of the specularly reflected electrons. The results have been compared with experimental data comprising both the damping of the oscillations and the recovery following a growth interrupt. The agreement between experiment and calculations is rather good. Moreover we could identify the mechanisms underlying the fast and the slow component of the recovery.
ADSORPTION MODELING OF POLYDIMETHYLSILOXANE ON SILICA: USING HEXAMETHYLDISILOXANE AS A MODEL PROBE
Authors: BARTHEL H. , RÖSCH L. , WEIS J.
Published: December 2003

Surface interactions play a most important part in the reinforcement of silicone elastomers, owing to the adsorption of the polydimethylsiloxane (PDMS) chain on the filler surface. The impact of the silylation of surface silanol groups on the surface structure and activity is of high technical interest. Hexamethyldisiloxane is an appropriate volatile probe to model the adsorption interactions of the PDMS polymer. In this study we investigated the static-volumetric gas adsorption of hexamethyldisiloxane on hydrophilic and silylated fumed silica, modified by dimethylsiloxy and trimethylsiloxy groups. The degree of silylation was controlled by the silanol content of the silica surface. Adsorption isotherms are discussed in terms of the adsorption energy and the heterogeneity of the active sites of adsorption.
AB INITIO STUDY OF THE STRUCTURAL AND ELECTRONIC PROPERTIES OF ADSORBATES: CO ON Cu(001)
Authors: DAL CORSO ANDREA , BALDERESCHI ALFONSO
Published: December 2003

We present an ab initio study of the structural, electronic and vibrational properties of CO on Cu(001). We use density functional theory in the local density approximation (DFT-LDA) and Vanderbilt ultrasoft pseudopotentials. A full structural minimization of the clean Cu(001) surface, of the 1 × 1 and c(2 × 2) CO covered surfaces is performed. The first layer of the clean surface relaxes inwards by -3.1%, while the first Cu layer of the 1 × 1 CO covered surface relaxes outwards by +0.5%. On the c(2 × 2) surface the Cu atoms directly under CO relax outwards by 0.7%, while the others relax inwards by -2.5%. The electronic structure and the work function of the relaxed surfaces are presented. Preliminary results for the CO vibrational frequencies are given in the limit of full coverage.
LOCAL DIPOLE FIELD CONTRIBUTIONS TO BOND-STRETCHING SILICON–HYDROGEN VIBRATIONAL MODES ON FLAT AND VICINAL Si(111) SURFACES
Authors: YANG H.-Y. , LUCOVSKY G.
Published: December 2003

Bond-stretching frequencies for bonded-H (and D) on flat and vicinal Si(111) surfaces have been calculated using a model that includes (i) short range valence forces and (ii) dynamic effects due to dipole–dipole interactions. Dipole–dipole interactions have been calculated exactly for flat surfaces, and for vicinal surfaces off-cut in the [Formula: see text] and [Formula: see text] directions terminated respectively by monohydride, Si–H, and dihydride, Si–H 2, bonding at the step edges. Using short range force constants and effective charges obtained from isolated Si–H and Si–H 2 stretching modes in hydrogenated amorphous Si, a-Si:H, as input parameters, the calculated coupled mode frequencies are in excellent agreement with experiment, i.e. using 5 empirical parameters, 16 frequencies in the range of 1500–2150 cm-1 are fit to better than 0.14%, or ±2–3 cm-1.
LIQUID GROOVING AT INTERFACES
Authors: APIKHTINA I. , BELOUSOV V. , BOKSTEIN B. , KLINGER L.
Published: December 2003

Under certain conditions a close contact between solid polycrystalline materials and the liquid phase leads to liquid grooving — formation of liquid grooves at grain boundaries. The liquid grooves (LG) make up a coupled liquid structure — liquid channel grain boundary structure (LGBS), so-called matrix distributed structure. This paper deals with kinetic data involved in the process of LG and LGBS formation. The novel models of LG and LGBS formation are elaborated.
THE CASE FOR ORDER-N METHODS IN LEED THEORY
Authors: PENDRY J. B.
Published: December 2003

Low energy electron diffraction experiments have superb sensitivity to surface structure, but rely on sophisticated theory for their interpretation. Advances in computer power, and developments in the theory itself, enable us to handle surface structures of moderate complexity. For future advances we must look to a completely new approach and the case is made for order-N methods which follow the time evolution of a point source of electrons to generate all beams for all angles of incidence and all energies in one shot.
COMPARISON OF THE SPIN POLARIZATION OF THE PHOTOELECTRON DIFFRACTION SPECTRA FOR DIFFERENT STRUCTURE MODELS OF MAGNETITE (111) LAYERS
Authors: RENNERT P. , CHASSÉ A. , MÜCK W.
Published: December 2003

Layers of magnetite structure were observed in deposing iron oxide on Pd by LEED measurements. We consider the magnetic structure of these layers. It is investigated whether spin-polarized and angle-resolved photoelectron diffraction can be used to dstinguish between the Zuo and the Mizoguchi model, respectively. In the two models we have a different distribution of the Fe 2+ and Fe 3+ ions. This difference is incorporated into the calculation by spin-dependent scattering phase shifts. The results of the calculation show that there is a cancellation of the magnetic scattering in the Mizoguchi structure whereas there remains a contribution in the Zuo model. Thus, we conclude that these structures should be distinguishable by spin-polarized angle-resolved photoelectron diffraction.
DIFFRACTION OF SPIN-POLARIZED Cu 3p PHOTOELECTRONS
Authors: ROTH CH. , KINOSHITA T. , ROSE H. B. , HILLEBRECHT F. U. , KISKER E.
Published: December 2003

We measured the spin–orbit-induced spin polarization in Cu 3p photoemission for fixed angle between light incidence and electron collection, while varying the emission angle relative to the crystal lattice. The polarization is found to vary strongly with emission direction in both sublevels. However, the ratio between the polarizations of the j=3/2 and j=1/2 sublevels is close to -1/2 for all emission directions. The spin polarization and its dependence on emission direction can both be viewed as arising from the angular momentum character of the final state wave which is imposed by the excitation conditions.
INFLUENCE OF PHOTOELECTRON DIFFRACTION ON MAGNETIC LINEAR DICHROISM
Authors: ROSE H. B. , KINOSHITA T. , ROTH CH. , HILLEBRECHT F. U. , KISKER E.
Published: December 2003

We studied the influence of photoelectron diffraction on magnetic linear dichroism and spin polarization in Co and Fe 3p photoemission excited by linearly polarized synchrotron radiation. We find a strong variation of the magnetic linear dichroism with emission direction. The spin polarization related to the spin–orbit interaction varies in a similar manner. This angular variation closely tracks that of the magnetic dichroism. In contrast, the exchange-induced spin polarization (-12+2)% does not vary appreciably with emission angle. These findings suggest that the main cause for the observed effects is the angular momentum character of the photoelectron wave.
MAGNETIC DICHROISM UNDER EXCITATION BY UNPOLARIZED RADIATION
Authors: FANELSA A. , SCHELLENBERG R. , HILLEBRECHT F. U. , KISKER E.
Published: December 2003

Magnetic dichroism has been observed in the angular distribution of p-core level photoemission spectra excited from crystalline ferromagnets by unpolarized X-rays. The angular dependence of the angular and energy-resolved photoemission intensity was recorded as a function of the emission direction with respect to the crystal, revealing a strong variation of the magnetic dichroism with emission angle due to photoelectron diffraction. This variation is particularly strong around the forward scattering peaks, including sign reversals close to these directions. The results demonstrate that any standard X-ray photoelectron spectroscopy apparatus possesses the potential for combined analysis of surface magnetic structure and geometric structure in a chemically specific way.
CORRELATION EFFECTS IN PHOTOEMISSION SPECTROSCOPY: Cl/Si(100)-(2 × 1)
Authors: REFOLIO M. C. , SANCHO J. M. LÓPEZ , SANCHO M. P. LÓPEZ , RUBIO J.
Published: December 2003

Different calculations of the electronic structure of this system have been unable to explain satisfactorily some puzzling features of the experimental surface band structure measured by angle-resolved photoemission (namely, the absence of any adsorbate structure near the Fermi level and the extremely small dispersion of all the adsorbate bands). Here we present a new calculation based on the lattice Anderson model in the (adsorbate) low-density regime. The one-electron Green function is computed directly from its Lehmann representation in terms of N-1 and N+1 electron states. These are obtained approximately with a new configuration interaction approach supplemented by renormalization group techniques in order to include iteratively states with an increasing number of electron–hole pairs. The resulting spectral function is in quantitative agreement with the photoemission spectrum: (1) all the adsorbate features lie between 5 and 10 eV below the Fermi level and (2) the adsorbate band dispersion is small (less than 0.5 eV). We also compare with the random phase approximation.
INFLUENCE OF SURFACE EXCITONS ON PHOTOCURRENT ACROSS THE SEMICONDUCTOR–ELECTROLYTE INTERFACE
Authors: AROUTIOUNIAN V. M. , MELICKSETIAN V. A. , MARGARIAN H. L. , KESOYAN A. L.
Published: December 2003

The analysis of spectral characteristics of the photocurrent of electrodes on the base of CdTe, CdS, InSe evidenced the formation of the two-dimensional subbands on the semiconductor surface when the photoelectrode is in contact with an electrolyte. Under illumination optical transitions between such subbands and bulk bands lead to formation of surface excitons.
INFLUENCE OF OPTICAL EXCITATION OF TWO-DIMENSIONAL SURFACE SUBBANDS ON PHOTOCURRENT ACROSS SEMICONDUCTOR–ELECTROLYTE INTERFACE
Authors: MARGARIAN H. L. , MELICKSETIAN V. A. , AROUTIOUNIAN V. M.
Published: December 2003

It was shown that in the case of TiO 2 contacted with an electrolyte, optical transitions of electrons from the valence band to the two-dimensional surface subband located near the conduction band or covered with the band.
MODULATED ELECTRON EMISSION
Authors: VALERI SERGIO
Published: December 2003

Basic aspects of energetic electron–atom scattering suffered by incident (primary) and/or excident (Auger, backscattered) electrons during propagation in (at least locally) ordered solids are reviewed. Scattering interference results in the dependence of total or partial electron yield on the incidence and/or takeoff angle. This paper is focused on processes experienced by incident electrons. The incident wave amplitude is spatially modulated within the solid by the interference of the unscattered wave portion and the wave portion scattered at the atomic sites. Interplay between forward focusing and multiple-scattering induced defocusing processes determines the profile of the primary electron intensity anisotropy along atomic chains. This anisotropy profile has been found to be a key parameter to interpret and to model modulated electron emission results. Examples are shown. They include (i) structural characterization of multilayer epitaxial growth, and (ii) study of the very early stage of III–V semiconductors amorphyzation by ion bombardment.
OBTAINING SURFACE LOCAL ATOMIC STRUCTURE BOND LENGTHS FROM SECONDARY ELECTRON EXTENDED FINE STRUCTURE: INVERSE PROBLEM SETTING AND SOLVING FOR COPPER
Authors: GUY D. E. , DEEV A. N. , RUTS YU. V. , GREBENNIKOV V. I. , SOKOLOV O. B.
Published: December 2003

The oscillation in the secondary spectra (extended fine structure) contains the surface (~ 3–5 atomic layers) local atomic structure information in the form of the radial distribution function. For the latter determination from the 3d metals secondary electron extended fine structure the inverse problem has been setting. On this basis the mathematical treatment of the experimental copper spectra was performed. The separation of the first three peaks and their approximately right positions in the calculation result was obtained.
OBTAINING COORDINATION NUMBERS FROM EELFS SPECTRA
Authors: SURNIN D. V. , DENISOV D. E. , RUTS YU. V.
Published: December 2003

The electron energy loss fine structure (EELFS) method allows one to obtain information on atomic bond lengths from the surface to the bulk. But gaining more complete quantitative information for example on coordination numbers has not presently been realized. The possibility of obtaining normalized radial distribution functions (RDF's) is shown for EELFS spectra which may be used for deriving complete structural information on pure elements. RDF's were obtained by using the regularization algorithm (after A. N. Tikhonov). The method for obtaining the RDF's was applied to the experimental Fe M 2,3 EELFS spectrum.
EFFECTS OF SURFACE LOSS IN REELS SPECTRA OF SILVER
Authors: TÖKÉSI K. , KÖVÉR L. , VARGA D. , TÓTH J. , MUKOYAMA T.
Published: December 2003

The energy distribution of the electrons backscattered in the direction of the surface normal of polycrystalline silver samples was studied using reflected electron energy loss spectroscopy (REELS) at 200 eV and 2 keV primary beam energies. For modeling the electron scattering processes, the Monte Carlo simulation technique was used and the REELS spectra were calculated at various (25°, 50° and 75°, with respect to the surface normal) angles of primary beam incidence. The effects of the surface energy loss process in REELS are evaluated from the comparison of the experimental and simulated spectra.
MULTIPLE SCATTERING CALCULATIONS OF GBMEED
Authors: KORTE U.
Published: December 2003

A method for computing grazing-incidence backscattering medium energy (1–3 keV) electron diffraction (GBMEED) is presented. The technique was recently proposed as a structural tool exhibiting diffraction effects resembling those of XPD. In GBMEED the intensity of quasielastically thermal diffuse scattering is measured at large scattering angles such that different atoms can be assumed to vibrate independently, and thus represent localized sources for diffuse scattering in the surface layers. The basis of the calculations is the multiple scattering theory of diffuse RHEED adopted to the medium energy case with a vibrating atom as source of diffuse scattering. Calculated plots of the intensity versus azimuthal/polar exit angle for an In overlayer on Si(111) show the forward focusing effect along the source-scatterer direction (well known from XPD) and further fine structure.
SHORT-RANGE ORDER OF DISORDERED SOLID SURFACES FROM ELASTICALLY SCATTERED ELECTRON SPECTRA
Authors: BONDARCHUCK O. , GOYSA S. , KOVAL I. , MEL'NIK P. , NAKHODKIN M.
Published: December 2003

The diffraction phenomenon of low- and middle-energy electrons for disordered solid surfaces was experimentally studied and a new electron spectroscopy technique for surface short-range order parameter determination proposed.
SURFACE STRUCTURES AND SURFACE CONDUCTANCE DURING METAL ADSORPTION ON SEMICONDUCTORS
Authors: INO S.
Published: December 2003

Epitaxial growth modes for "two-step deposition" processes of metals on a Si(111) surface were investigated. Depth distributions of composition during the growth were analyzed by using RHEED-TRAXS (total reflection angle X-ray spectroscopy). We first made [Formula: see text]-(Ag, Au, Ga), [Formula: see text]-Sn and (4×1)-In structures, and then second metals (Ag, Au, Sn, Ga and In) were deposited on these surfaces at room temperature. Growth processes observed are classified into five growth modes: ordinary growth (O), alloying growth (A), substitution atom growth (S), particle formation growth mode (P) and floating atom growth (F).

During the growth processes, we measured also surface conductivities which showed interesting behaviors. These results can be partly understood considering the growth modes, atomic arrangement, surface composition, Fermi level pinning and band bending, etc.
STRUCTURAL ANALYSIS OF IMPERFECT CRYSTAL SURFACES BY REFLECTION HIGH-ENERGY ELECTRON DIFFRACTION: ANTIPHASE DOMAINS OF A ${\rm Si}(111)(\sqrt 3
\times\sqrt 3)$-Ag SURFACE
Authors: ICHIMIYA AYAHIKO , OHNO YUSUKE
Published: December 2003

For dynamical calculations of reflection high-energy electron diffraction (RHEED) for imperfect crystal surfaces, a general formula of Fourier coefficients of crystal potential with domain structures is developed. Using the formula, RHEED intensity rocking curves are calculated for a [Formula: see text]-Ag surface with antiphase domains. We discuss effects of antiphase domains of surfaces in structure determinations by RHEED.
HOLOGRAPHIC LEED: A REVIEW OF RECENT PROGRESS
Authors: SALDIN D. K. , CHEN X. , VAMVAKAS J. A. , OTT M. , WEDLER H. , REUTER K. , HEINZ K. , DE ANDRES P. L.
Published: December 2003

We review the basic ideas of holographic LEED, and the latest progress in the field. We compare several proposed computer reconstruction schemes. Using experimental diffuse LEED data from O/Ni(001) and K/Ni(001) surfaces, we show that the capability now exists for filtering out the effects on the diffraction patterns of possible long-range order amongst the adsorbates, thus making holographic LEED much more analogous to photoelectron holography. Inclusion of a scattered-wave kernel to compensate for the variation of the magnitude of the reference wave at the positions of potential object-wave sources enables the reconstruction of a fully three-dimensional image of substrate atoms in the immediate vicinity of atomic adsorbates from a set of just normal-incidence diffuse LEED patterns.
ATOMIC RESOLUTION STM OF THE NiO (001) SURFACE STRUCTURE AND DEFECT SITES: c(2×2) PATTERNING AND EFFECTS OF COVALENT BONDING
Authors: CASTELL M. R. , DUDAREV S. L. , WINCOTT P. L. , CONDON N. G. , MUGGELBERG C. , THORNTON G. , NGUYEN MANH D. , SUTTON A. P. , BRIGGS G. A. D.
Published: December 2003

Elevated temperature STM has been used to obtain atomic resolution images of flat regions, defect sites and step edges on the (001) surface of crystalline nickel oxide. Identification of surface lattice sites seen in empty and filled states (nickel and oxygen sites, respectively) is consistent with recent theoretical results according to which NiO is a charge transfer insulator with strongly correlated electrons. It has been found that certain surface defects lead to the formation of spatially delocalized hole states resulting in c(2×2) patterning in STM images. The appearance of this patterning points to the presence of a substantial covalent contribution to chemical bonding in NiO.
MEASUREMENTS OF SPECTRAL RESOLVED PHOTON INTENSITY MAP FOR METAL PARTICLES BY STM
Authors: NISHITANI R. , UMENO T. , KASUYA A. , NISHINA Y.
Published: December 2003

We have measured for the first time the spectral resolved photon maps of the light induced by scanning tunneling microscopy (STM) of noble metal particles on the graphite surface. The photon intensity as a whole is linearly correlated with the height of the topography of the samples. The photon map changes depending on the wavelength of the light collected. The position-dependent contrast besides the height-dependent contrast is obtained by normalizing the photon map with the corresponding STM topography. The normalized photon maps show that the spectral modes of the light emitted are varied with the tip position on the particles. The result shows that the contrast of the photon map is dependent on both the sample topography and the tip shape. A measurement of an isochromat photon map is also made for the mixture of gold and silver metals for a chemical analysis.
SURFACE MODIFICATIONS: NANOSTRUCTURES AND NESTED POLYHEDRA GENERATED BY PULSING THE STM TIP
Authors: HERSHFINKEL M. , GHEBER L. A. , HOMYONFER M. , TENNE R. , VOLTERRA V.
Published: December 2003

STM experiments were performed to study modifications on the surface of crystalline and amorphous transition metal chalcogenides. Pulses with different parameters were applied to the STM tip, at predefined locations, while scanning the surface of WSe 2 and MoS 3. Different types of structures were formed on the crystalline WSe 2 surface: (a) holes, (b) mounds, (c) ringlike structures. The three types were formed at different ranges of voltage. In some cases local cleavage of the surface was observed. An explanation is offered for the creation of such a variety of structures. On the amorphous MoS 3 surface the pulses created small, round mounds. The size of the structures grows with the voltage of the applied pulse. I–V characteristics taken on these structures show semiconducting behavior with a gap of 1.1 eV, similar to the gap of bulk MoS 2. TEM images show that nested polyhedral structures are formed in the STM experiments, with sizes that agree with the observed structures. Similar round crystalline structures are formed on the surface of MoS 2 grown under different conditions. This is the first time that such crystallization is observed by pulsing the STM tip.
DETECTION OF SPATIAL DISTRIBUTION OF THE TUNNELING CURRENT DISPERSION OF STM
Authors: KURNOSIKOV O. V. , PEROV P. YU. , GROSHENKO N. A.
Published: December 2003

Noise and fluctuations of tunneling current of STM can be analyzed for a surface investigation. The tunnel gap can behave as a passive element, which transforms the noise in the sample–tip-piezodriver system and as an active source of noise due to the stochastic character of polarization and relocation of adsorbed molecules in the near-tip region. A spatial distribution of dispersion of the tunneling current of STM operated in air was detected. The samples of Cu, Nb, C (graphite), Pb, Zn, SnO 2, Si were studied. The regions with a high dispersion value formed dots, spots and lines. During several sequence scannings of surface by tip some spots can vanish. The connection of the observed dispersion with relief features and with the picture of the barrier height distribution is discussed. The simple model of the noise source is proposed.
ULTRAHIGH VACUUM ATOMIC FORCE MICROSCOPY: TRUE ATOMIC RESOLUTION
Authors: LÜTHI R. , MEYER E. , BAMMERLIN M. , BARATOFF A. , HOWALD L. , GERBER CH. , GÜNTHERODT H.-J.
Published: December 2003

In this note we report the first observation of salient features of the Si(111)(7×7) reconstructed surface across monatomic steps by dynamic atomic force microscopy (AFM) in ultrahigh vacuum (UHV). Simultaneous measurements of the resonance frequency shift Δf of the Si cantilever and of the mean tunneling current [Formula: see text] from the cleaned Si tip indicate a restricted range for stable imaging with true atomic resolution. The corresponding characteristics vs. distance reveal why feedback control via Δf is problematic, whereas it is as successful as in conventional STM via [Formula: see text]. Furthermore, local dissipation (energy loss of 10-14 W) through individual atoms is observed and explained by the coupling of the surface atoms to phonons.
TESTING THE FRICTIONAL PROPERTIES OF MoO3 THIN FILM SURFACE WITH AFM: A NANOSCOPIC LEVEL INVESTIGATION
Authors: KLEIN H. , PAILHAREY D. , MATHEY Y. , TORREGROSSA F.
Published: December 2003

In this study we have realized α-MoO 3 thin film synthesis, mainly under the (110) orientation, and performed their frictional study using an AFM to obtain values of friction coefficients μ. This technique appears to be a good way for the investigation of the frictional properties at the microscopic scale. Indeed we can mark the difference between two crystalline states of MoO 3 by their frictional properties.
A RAY TRACING METHOD TO DESCRIBE THE ANGULAR PROFILES OF DIFFRACTION RODS IN SURFACE X RAY EXPERIMENTS
Authors: TORRELLES X. , ALVAREZ J. , FERRER S.
Published: December 2003

The accurate determination of the coordinates normal to the surface in X ray diffraction experiments requires measuring up to high exit angles. Under these conditions some instrumental and geometrical effects related to the dimensions of the detector slits and the location in the Ewald sphere of the outgoing beam may complicate the analysis of the data. We have developed a method based on the ray tracing technique to investigate the appropriate corrections. Examples for Ge(001)-(2×1) are presented.
SURFACE MAGNETISM INVESTIGATED BY LOW ENERGY ION SCATTERING IN THE GRAZING INCIDENCE MODE
Authors: NÄRMANN A. , SCHLEBERGER M. , DIRSKA M. , MANSKE J. , LUBINSKI G. , HOEKSTRA R.
Published: December 2003

When scattering ions off surfaces, some particles are neutralized into excited states that are subsequently de-excited by light emission. In the case of magnetic surfaces the information about the spin of the captured electron might be accessed via the polarization of the emitted light. In the grazing incidence mode the surface sensitivity is highest due to the fact that the particles do not penetrate into the target surface but are scattered well above the uppermost atomic layer. Thus the electrons that neutralize the incoming ion originate from the topmost layer. This implies that the method is very well suited for investigating the properties of magnetic surfaces and multilayers. We present a UHV setup that serves this purpose as well as some results obtained for magnetized Fe(110) surfaces.
MEASUREMENT OF SURFACE STRESS: DESCRIPTION OF AN INTERFEROMETRIC METHOD
Authors: DEGAND G. , MÜLLER P. , KERN R.
Published: December 2003

In a recent publication, we proposed a new experimental method for measuring the absolute surface stress of a thin crystalline sheet based on the deformation of very thin sheets (thickness e<10 μm) submitted to disymmetrical surface stresses (S1 on one side of the sheet, S2 on the other). This paper demonstrates that Michelson interferometry can be used to measure a surface stress change of 2–3 10-3 J·m -2 if the thickness and the Young modulus of the sheet are accurately known. Using a silicon substrate sample we found that one fourth of a monolayer of silver reduces the surface stress by 0.45 J·m -2.
INVESTIGATIONS OF THE SEMICONDUCTOR–ELECTROLYTE INTERFACE IN THE PRESENCE OF THE LONGITUDINAL AND CROSS SURFACE FIELDS
Authors: MELICKSETIAN V. A. , AROUTIOUNIAN V. M. , MARGARIAN H. L.
Published: December 2003

The method of investigation of the illuminated semiconductor–electrolyte interface by using longitudinal and cross surface fields was suggested. The complex analysis of obtained spectral dependences at different values of applied fields allows one to make suppositions about criteria which determine which process — the motion along the surface or transfer across the interface — is dominated at the corresponding conditions.
METHOD OF SURFACE STATE INVESTIGATION AT LOW TEMPERATURES
Authors: AROUTIOUNIAN V. M. , MELICKSETIAN V. A. , MARGARIAN H. L. , KESOYAN A. L.
Published: December 2003

The method of investigation of the surface potential influence on the processes taking place at the illuminated semiconductor–electrolyte interface is suggested. The experimental data evidenced in particular the formation and followed dissociation of surface exciton.
ON THE THEORY OF THE ADSORPTION OF A GAS ON A SEMICONDUCTOR
Authors: AROUTIOUNIAN V. M. , AGHABABIAN G. S.
Published: December 2003

It is shown that a charging of the surface of a semiconductor by electrons can lead to an effective increase of the desorption, a new term in the kinetic equation and as a result the appearance of new regularities — both in the adsorption isotherm and in the kinetic equation. We point out the range of applications of the Langmuir and Henry theories as well as mentioned references where one observed root dependences of the surface conduction on the pressure by experiment.
GENERAL METHOD TO SELECT CONVENIENT LATTICE VECTORS ON A SURFACE WITH ARBITRARY MILLER INDICES
Authors: HERMANN K.
Published: December 2003

Many theoretical methods dealing with electronic and structural properties of single crystal surfaces rely on a convenient description of the surface and bulk periodicity at the same time. This can be achieved by using surface adapted lattice vectors [Formula: see text], where vectors [Formula: see text] define (h k l) net planes parallel to the surface while [Formula: see text] connects adjacent (h k l) net planes. For selected low index (h k l) surfaces of common crystals the construction of appropriate lattice vectors may be trivial. However, the general problem of determining a lattice basis adapted to a surface orientation which is described by Miller indices (h k l) in a general crystal lattice is more involved. In this paper we show that such bases, [Formula: see text], can be uniquely determined by linear transformations from the bulk lattice basis [Formula: see text]. The transformations depend on Miller indices (h k l) but not on the lattice type and can be quantified by number-theoretical methods. Thus, they are numerically stable and can be easily implemented in computational algorithms dealing with surfaces of most general crystals.
THE SURFACE STRUCTURE DATABASE: SSD
Authors: VAN HOVE M. A. , HERMANN K. , WATSON P. R.
Published: December 2003

The second version of SSD (Surface Structure Database) appeared in 1996, updating its first version, published in 1993. SSD-2 includes nearly 1000 structure analyses (an increase of 64%) published through mid-1995, as well as numerous software extensions and improvements. SSD is an interactive PC-based database of experimentally determined surface structures. For maximum reliability and usefulness, the structures are critically selected to be completely solved, by established techniques. The database includes extensive information not only about atomic positions, bond lengths and angles, but also about experimental preparation, measurement and analysis methods. The main features of SSD include an advanced search and display system, as well as interactive 3D color visualization and analysis tools of great flexibility. It is also possible to generate publication-ready color or gray-scale prints of any structure. A printed version of SSD-1, called "Atlas of Surface Structures," is available and also described here.
Solution of time‐varying singular nonlinearsystems by single‐term Walsh series
Authors: Sepehrian B. , Razzaghi M.
Published: December 2003

A method for finding the solution of time‐varying singular
nonlinear systems by using single‐term Walsh series is proposed.
The properties of single‐term Walsh series are given and are
utilized to find the solution of time‐varying singular nonlinear
systems.
Robust dissipativity for uncertain impulsive dynamical systems
Authors: Liu Bin , Liu Xinzhi , Liao Xiaoxin
Published: December 2003

We discuss the robust dissipativity with respect to the quadratic
supply rate for uncertain impulsive dynamical systems. By
employing the Hamilton‐Jacobi inequality approach, some sufficient
conditions of robust dissipativity for this kind of system are
established. Finally, we specialize the obtained results to the
case of uncertain linear impulsive dynamical systems.
Analytical investigations of the Sumudu transformand applications to integral production equations
Authors: Belgacem Fethi Bin Muhammed , Karaballi Ahmed Abdullatif , Kalla Shyam L.
Published: December 2003

The Sumudu transform, whose fundamental properties are
presented in this paper, is little known and not widely used.
However, being the theoretical dual to the Laplace
transform, the Sumudu transform rivals it in problem solving.
Having scale and unit‐preserving properties, the Sumudu transform
may be used to solve problems without resorting to a new
frequency domain. Here, we use it to solve an integral
production‐depreciation problem.
Study of a least‐squares‐based algorithm forautoregressive signals subject to white noise
Authors: Zheng Wei Xing
Published: December 2003

A simple algorithm is developed for unbiased parameter
identification of autoregressive (AR) signals subject to white
measurement noise. It is shown that the corrupting noise
variance, which determines the bias in the standard least‐squares
(LS) parameter estimator, can be estimated by simply using the
expected LS errors when the ratio between the driving noise
variance and the corrupting noise variance is known or obtainable
in some way. Then an LS‐based algorithm is established via the
principle of bias compensation. Compared with the other LS‐based
algorithms recently developed, the introduced algorithm requires
fewer computations and has a simpler algorithmic structure.
Moreover, it can produce better AR parameter estimates whenever a
reasonable guess of the noise variance ratio is available.
Positive solutions of some nonlocal boundary value problems
Authors: Infante Gennaro , Webb J. R. L.
Published: December 2003

We establish the existence of positive solutions of some m‐point boundary value problems under weaker assumptions than previously
employed. In particular, we do not require all the parameters occurring in the boundary conditions to be positive. Our results allow more general behaviour for the nonlinear term than being either sub‐ or superlinear.
Three periodic solutions to an eigenvalue problem for a class ofsecond‐order Hamiltonian systems
Authors: Cordaro Giuseppe
Published: December 2003

We establish a multiplicity result to an eigenvalue
problem related to second‐order Hamiltonian systems. Under new
assumptions, we prove the existence of an open interval of
positive eigenvalues in which the problem
admits three distinct periodic solutions.
On real interpolation, finite differences, and estimatesdepending on a parameter for discretizations of elliptic boundary value problems
Authors: Guidetti Davide , Piskarev Sergei
Published: December 2003

We give some results concerning the real‐interpolation method and
finite differences. Next, we apply them to estimate the
resolvents of finite‐difference discretizations of Dirichlet
boundary value problems for elliptic equations in space
dimensions one and two in analogs of spaces of continuous and
Hölder continuous functions. Such results were employed to
study finite‐difference discretizations of parabolic equations.
On a zonal polynomial integral
Authors: Gupta A. K. , Kabe D. G.
Published: December 2003

A certain multiple integral occurring in the studies of
Beherens‐Fisher multivariate problem has been evaluated by Mathai
et al. (1995) in terms of invariant polynomials. However, this
paper explicitly evaluates the context integral in terms of zonal
polynomials, thus establishing a relationship between zonal
polynomial integrals and invariant polynomial integrals.