We have measured Ag K- and Au L_III-edge EXAFS (extended x-ray absorption fine structure) for Ag/Au core/shell particles. The structural parameters were obtained from EXAFS curve-fitting analyses and were discussed in comparison to the structure estimated from TEM (transmission electron microscope) analyses. The thickness of the shell and diameter of the core can be evaluated from EXAFS that are fairly consistent with the results estimated from TEM. From EXAFS two-shell model analyses the Ag-Ag distance decreases and Au-Au distance increases in the thinner shell. This result suggests that the electrons transfer from Ag atom to Au atom at the interface between core and shell atom. [DOI: 10.1380/ejssnt.2006.138]

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Low energy ion induced X-ray emission (LIIXE) from insulators is presented and discussed. Ions of light, such as He⁺ ions, or heavy, such as Ga⁺ ions, in energy from lower than 1 keV/AMU (atomic mass unit) to several keV are demonstrated to induce characteristic X-ray emission effectively from insulator samples. Features of LIIXE, such as using very low energy ions, no needs for conducting coating on surface of samples, and relatively high X-ray yields for low energy characteristic X-rays, make it prospective for being applied in materials analysis, especially for insulator materials containing light elements. A proto-type instrument under developing for measurement of the X-ray is introduced. [DOI: 10.1380/ejssnt.2006.144]

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Atomic force microscopy (AFM) is increasingly used in biological sciences not only for imaging but also for measuring force of interaction between bio-molecular pairs. To conduct the force measurement on various bio-molecular pairs more effectively, we propose a new experimental system using protein-polymer complex which is compose of ligand modified polymer and its receptors. This experimental system is expected to prevent target biomolecules from deactivation, and to distinguish the specific interaction between biomolecules of interest with ease from non-specific adsorption between tip of a cantilever and a substrate surface, since the biomolecules of interest are bound on the flexible polymer. In an initial trial, we applied it to measure the force of interaction between avidin and biotin using CM-cellulose as a base polymer. As a result, we got 60-160 pN interaction forces which are proportional to logarithm of force loading rate, which is consistent with the previously reported tendency. [DOI: 10.1380/ejssnt.2006.149]

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To clarify how Co reacts with a SiO₂ layer on Si substrates, the annealing processes were observed using low energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM). LEEM results using patterned substrate showed that Co silicide nano-dots form and that the Co diffusion length on the SiO₂ layer is very small. From PEEM observations of a SiO₂ layer with voids on Si substrate, we found that Co atoms in the void area remain because of the formation of silicides, but those on the SiO₂ surface disappear because metallic Co atoms easily diffuse. Co diffusion through the SiO₂ layer to the Si substrate can compatibly explain these two results. [DOI: 10.1380/ejssnt.2006.155]

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We demonstrate a novel way for the fabrication of the site-controlled Ga-droplets on GaAs(111)A surface based on oxide patterning process. The process is combined with the atomic force microscope tip-induced local area nano-oxidation and atomic hydrogen assisted oxide decomposition (AHAOD). The formation mechanism of Ga-droplets can be explained by the self-gathering effect of the Ga on the modified GaAs(111)A. Furthermore, we suggest the possibility of fabrication of ordered GaAs nanostructures by subsequent supplying of As flux on the site-controlled Ga-droplets. [DOI: 10.1380/ejssnt.2006.161]

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The atomic structure of the Ca induced Si(111)-(3×2) surface at 300 K has been investigated using X-ray photoelectron diffraction (XPD). After confirming the quality of the single-domain (3×2) surface by LEED, in which weak ×2 streaks were observed likewise the patterns reported in the literature, we have measured the Ca 2p core-level spectra within an azimuthal angle range of ±66°, where 0° corresponds to the direction perpendicular to the Ca chain, and at takeoff angles from 9° to 15° using the Mg Kα line. The experimental XPD patterns showed good agreement with the simulated XPD patterns of the T₄ site model, while the simulated XPD patterns of the H₃ model do not agree with the experimental results. Taking these results into account, we conclude that Ca atoms are adsorbed on the T₄ site at 300 K and thus that the weak ×2 streaks do not result from the presence of two adsorption sites as proposed in the literature. [DOI: 10.1380/ejssnt.2006.166]

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Surface-structure dependence of hydrogen-assisted reduction at oxidized Ni(110) surfaces was studied by metastable-induced electron spectroscopy (MIES) and low-energy electron diffraction (LEED). We prepared three different types of oxidized Ni(110) surfaces: (a) Low oxygen-coverage (3 × 1) surface; (b) moderate oxygen-coverage (2 × 1) surface; (c) high oxygen-coverage (3 × 1) surface. When exposed the surfaces (a) and (b) to hydrogen molecular gas at exposures 10∼100 L, their structures were changed to a hydrogen-adsorbed (1 × 1) structure. MIES clearly demonstrated a progress of hydrogen-assisted reduction by showing intensity decrease of the O2p-induced peak together with recovery in intensity of the Ni3d-induced peak and appearance of hydrogen-induced broad peak. Hydrogenated (1 × 1) surfaces, thus produced, were transformed to oxidized surfaces of the low-coverage (3 × 1) or (2 × 1) structure by being exposed to oxygen, depending on the oxygen exposure. These reduction/oxidation reactions took places reversibly. At the surface (c), however, such reactions were not observed in the range of hydrogen exposure up to 100 L at RT. This fact implies that the density of Ni-O-Ni atomic rows formed on the oxidized Ni(110) surfaces determines the progress of oxygen reduction reaction. [DOI: 10.1380/ejssnt.2006.170]

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The chemical bonding features and electronic states of ultrathin Ge oxide layers prepared on Ge(100) by UV-O₃ oxidation at room temperature or thermal oxidation at 550°C and 600°C were characterized by x-ray photoelectron spectroscopy (XPS) and total photoelectron yield spectroscopy (PYS), in comparison with those of ultrathin SiO₂/Si(100) cases. We have found that the oxidation of Ge(100) by UV-O₃ at room temperature proceeds in a layer by layer manner as well as the oxidation of Si(100) and that UV-O₃ oxidation rates of Ge(100) and Si(100) are almost the same at room temperature in the oxide thickness region below 1nm. From the analysis of the onset of energy loss spectra of O1_s and Ge2p_3/2 photoelectrons, the energy bandgap of the GeO₂ films was measured to 5.70±0.05 eV in the thickness range from 0.9∼1.9 nm, and the valence band offset at the interfaces between GeO₂ and Ge(100) was determined to be 4.00±0.05 eV. It is also confirmed from PYS measurements that ultrathin GeO₂/Ge(100) prepared by UV-O₃ oxidation contains defect states being about one order of magnitude larger than ultrathin SiO₂/Si(100) systems. [DOI: 10.1380/ejssnt.2006.174]

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We propose and fabricate a 1-bit adder circuit having only two single electron transistors (SETs) for AND and XOR logic operations by using SA-MOVPE. Two SETs have two common input gates and different Coulomb oscillation periods. The logic operation can be achieved on the basis of a binary decision diagram (BDD) architecture using Coulomb blockade (CB) in GaAs dots. We also demonstrate Coulomb oscillations caused by input gate voltages for a SET. Oscillation features of two input gates are the same and their phases can be shifted by the control gate. [DOI: 10.1380/ejssnt.2006.180]

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Attempts were made to form various nanostructures on InP substrates using anodization process. Surprisingly wide varieties of nanostructures were obtained. They included zigzag pore arrays and chaotic porous structures on (111)B substrate, and quasi-periodic straight nanopore arrays on (001) substrate. Straight pore samples showed blue-shifted peaks due to quantum confinement whereas no clear energy shifts were observed in (111)B samples. Zigzag and straight pore samples also showed red-shifted PL emissions probably due to emission from surface state continuum. [DOI: 10.1380/ejssnt.2006.184]

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Local barrier height (LBH) of Si(001) surface was studied using light-modulated scanning tunneling spectroscopy (LM-STS), which enables the observation of the tip-sample-dependent LBH with or without photoillumination simultaneously. The bias voltage and tip-sample distance dependence of LBH were comprehensively understood by the tip-induced band bending (TIBB), which influences the scanning tunneling microscopy and spectroscopy (STM/STS) in measurement of the local electronic structures of semiconductors. A marked decrease in surface photovoltage caused by photocarrier tunneling at shorter tip-sample distance was also shown. On the basis of these results, a method to measure LBH free of TIBB is discussed. [DOI: 10.1380/ejssnt.2006.192]

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We have investigated constant-height atomic force microscope images of a hydrogen-terminated silicon (100) 2× 1 surface including a methyl observed by a silicon tip with and without a hydrogen atom at the apex, using a density-functional-based tight-binding method. Using silicon-tip without hydrogen at the apex, we obtain good images with anisotropic spots reflecting the symmetry of methyl when observing with large tip-sample distance. Using silicon-tip with hydrogen at the apex, we expect to obtain better images showing internal hydrogen and carbon atoms of methyl if the forces can be measured precisely: they have atomic resolution for the image of adsorbed methyl. [DOI: 10.1380/ejssnt.2006.197]

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We report a parallel analysis of protein-surface interactions using an array presenting spots with different surface properties and a surface plasmon resonance (SPR) imaging apparatus. The array was fabricated by the photopatterning of self-assembled monolayers (SAMs) carrying different functional groups including methyl, hydroxyl, carboxylic acid, amine, and poly(ethylene glycol)-tethered amine. The SPR imaging apparatus was developed in-house. The adsorption behavior of bovine serum albumin (BSA) on SAMs was monitored by SPR imaging. The adsorption amounts obtained using the SPR imaging apparatus were well correlated with those obtained by the bicinchoninic acid (BCA) assay. The combination of the array and SPR imaging is suitable for high-throughput, real-time, label-free, and highly-sensitive studies of the interactions of proteins with surfaces with various properties. [DOI: 10.1380/ejssnt.2006.201]

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We have done scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS) as well as current imaging tunneling spectroscopy (CITS) of an Al nanocluster periodic array of a submonolayer-Al/Si(111) system. To understand the formation mechanism of this system in detail, a phase diagram of the Al/Si(111) has been carefully produced. Among several structural phases, the nanocluster phase appears for the deposition thickness of 0.24-0.5 ML at a substrate temperature of 550°C. It has been confirmed that these growth conditions should be carefully chosen to produce the well-defined nanocluster. The site-resolved STS spectra of Al nanocluster at 78 K show an insulating energy gap of 3.3 eV. In the CITS images, we have found different features of space-resolved tunneling current for the filled and empty states, which markedly depend on atomic sites and also on inequivalent half-unit cells. [DOI: 10.1380/ejssnt.2006.208]

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We report results of XAFS measurements and analysis on nanocrystalline selenium embedded in amorphous matrix. Nanocrystalline selenium samples were produced by annealing amorphous selenium powder synthesized by wet-method. From EXAFS analysis of fully crystallized selenium samples we discuss two different mode of crystallization, i.e. chain-folding and atomic rearrangement processes. In the case of crystallization by annealing EXAFS results support the chain-folding model. Amorphous/crystallites two phase model can not account for the measured EXAFS spectra of nanocrystalline systems, suggesting existence of interfacial region which has anomalously large volume between the amorphous and the crystalline phase. Curve-fitting analysis of the EXAFS spectra provided lower coordination number and larger third order cumulant than expected from the two phase model, reflecting structural characteristics of the interfacial region. Implications of these results concerning the mechanism of nanocrystallites formation in amorphous matrix are discussed. [DOI: 10.1380/ejssnt.2006.213]

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The oxidation process of an HfC(100) surface has been investigated by photoemission spectroscopy utilizing synchrotron radiation. When the HfC(100) surface is exposed to O₂ at room temperature, the C atoms in the surface region are depleted, and the substrate's Hf atoms are oxidized by stepwise reactions and are finally oxidized to form an HfO₂-like layer at high coverages (> 10 L). When the surface exposed to 10 - 50 L of O₂ is heated, the work function decreases with increasing heating temperature. The work function reaches its minimum value, which is lower than that of the clean surface by 1.2 eV, by heating the surface exposed to 10 L (50 L) of O₂ at 1000 - 1100°C (1100- 1200°C). The oxidized layer which gives the minimum work function is proposed to be mostly composed of oxycarbides, and a part of the surface is proposed to be covered by an HfO-like layer. [DOI: 10.1380/ejssnt.2006.219]

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We have studied phonon mode behavior in GaN nanocolumns and GaN/AlN multiple quantum disk nanocolumns, which are self-organized on Al₂O₃ and Si by RF-MBE, by means of Raman scattering. In GaN nanocolumns, we observe a Fröhlich mode localized at the surface of nanocolumns. The frequency and line width strongly depend on the column density and its inhomogeneity. It is demonstrated that Raman scattering is a useful method to characterize the crystal properties of the nanocolumns. In GaN/AlN multiple quantum disk nanocolumns, we observe several confined, quasi-confined and interface phonon modes, whose wave vectors along the axial direction may be quantized by the columnar nanostructures. [DOI: 10.1380/ejssnt.2006.227]

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We have developed a simple and reliable method for preparing single-atom tips. Electrochemical techniques are applied to deposit a noble metal film on the W <111> tip. With the protection of the metal film, the tip can be stored and transferred in the ambient condition. After a gentle annealing of the plated tip in vacuum, a thermally and chemically stable nano-pyramid with single atom sharpness can be generated at the tip apex. The atomic structure of the tip is imaged by a field ion microscope (FIM) layer by layer through field evaporation. The corresponding field emission patterns can also be determined by the field emission microscopy (FEM). Most importantly, the single atom sharpness as well as the pyramidal structure can be regenerated for tens of times in vacuum simply by annealing if the apex is accidentally damaged. Field emission measurements indicate that the single-atom tips can emit stable electron beams of high brightness with a small extension angle. These desirable features make the single-atom tips very promising for future applications. [DOI: 10.1380/ejssnt.2006.233]

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Effects of structural defects on thermal transport in carbon nanotubes are revealed through nonequilibrium molecular-dynamics simulations with the Tersoff-Brenner bond-order potential. The thermal conductivity of carbon nanotubes decreases rapidly down to 25 % with only 1 % vacancy defects. By performing thermal annealing, the vacancy defects are mainly transformed into 5-6 defects consisting of pentagon-hexagon pairs, and the reduced thermal conductivity due to vacancy defects is increased by 4-7 %. This improvement in thermal conductivity can be understood from the result that the thermal resistance of the 5-6 defects is smaller than that of the vacancy defects. [DOI: 10.1380/ejssnt.2006.239]

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Recently, we have found that alcohols adsorbed on the silica surface in non-polar liquids (cyclohexane, etc.) form ordered structures extending to several tens of nanometer through hydrogen bonding between the surface silanol groups and the adsorbed alcohols as well as between the adsorbed alcohols. We call this structure the surface molecular macrocluster. Surface forces measurement has revealed that the long range attraction appears from distances about twice of the macrocluster layer thickness. The bridging of the adsorption layers brings about the long range attraction due to the interfacial energy between the adsorption layer of molecular macroclusters and the bulk solution. In this study, the interfacial energies (γ) between the methanol adsorption layer and the bulk solution were evaluated by analyzing the long range attraction as well as pull-off force in methanol-cyclohexane binary liquid mixtures. The interfacial energy (γ) was evaluated to be 7.2 ± 0.3 mN/m, which was more than 10 times larger than that for methanol/cyclohexane interface at the phase separation (0.6 mN/m). This larger interfacial energy should be caused by the rather fixed orientation of methanol molecules at the interface due to the ordered structure of methanol molecules in a macrocluster. [DOI: 10.1380/ejssnt.2006.244]

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A tripod molecule with an azobenzene arm was designed as a single-molecular tip for noncontact atomic force microscopy (NC-AFM), where photoswitching of the tip apex can change the probe function by the external stimulus. NC-AFM imaging on the synthesized molecules revealed that they can be strongly fixed on Au surfaces in isolated form and reversibly switch between trans- and cis-form by irradiation at selected wavelength of light. [DOI: 10.1380/ejssnt.2006.249]

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The dynamics of the zinc and the oxygen adatom supplied as atomic zinc and atomic oxygen on the 6H-SiC(0001) surface is investigated using the first-principles calculation. The result reveals that the on top site is unstable for the zinc and the oxygen on the 6H-SiC(0001) surface. However, the oxygen is stable at the on top site near a Zn adatom. Our calculation shows that the optimized growth condition for the growth of ZnO on 6H-SiC(0001) is Zn-polarity ZnO crystal grown under the stoichiometric growth condition. [DOI: 10.1380/ejssnt.2006.254]

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A size and condensation controlled Pd nanoparticle is reported. The Pd nanoparticles are prepared by a gas condensation method with He gas, so called dry process. A fabrication of the nanoparticle by means of the dry process is an excellent way, because there are little contaminations on the most lateral surface of the nanoparticle than the nanoparticle by the wet process. Characterizations by TEM and AFM show that the fabricated Pd nanoparticle has a spherical shape, a few nm size in diameter and highly dispersed on the substrate. It is found that there are two chemical states in the Pd nanoparticle. One is an oxidized part at the surface and the other is a bulk part. [DOI: 10.1380/ejssnt.2006.258]

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We have investigated the mechanism of Zr silicidation from ZrO₂/Si gate-stack structure in ultralarge-scaled-integration devices by high-resolution core-level photoemission spectroscopy with annealing-temperature controlling. We have found that the interfacial SiO₂ layer thickness is tunable by controlling the annealing temperature and the silicidation occurs in the narrow annealing-temperature ranges. New method by combinatorial annealing system enables to control the narrow-range annealing temperature for the observation of the silicidation processes and to discuss the silicidation chemical reaction thermodynamically based on the annealing-temperature dependence in core-level photoemission spectra. [DOI: 10.1380/ejssnt.2006.263]

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When a system having a series of non-covalently bonded multiple components is pulled to opposite directions from its two ends, sequential and/or simultaneous bond breakages take place. The probability of breakage of individual bonds depends on their intrinsic mechanical properties and on the experimental conditions. We are particularly interested in the pulling mechanics observed when a lectin functional AFM probe was used to pull out the membrane protein, glycophorin A of the red blood cell, together with lipid tether formation. Here our concern is which of the non-covalent interactions, i.e., lectin-glycophorin A or lipid-lipid interactions in the tether is disrupted when the probe is detached from the biomembrane surface. In this paper we conclude that, during the process of lipid tether elongation with a constant tensile force of ∼ 70-80 pN, unbinding of the lectin from glycophorin A takes place with a finite probability in addition to tether breakages that includes complete or incomplete delipidation of glycophorin A. [DOI: 10.1380/ejssnt.2006.273]

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Carbon nanotube (CNT) tip for scanning tunneling microscopy (STM) is fabricated directly on a tungsten tip by microwave plasma-enhanced chemical vapor deposition (MPECVD). The reduction of the density of plasma ions directed to the apex of the tungsten tip suppresses the sputtering effect, and makes a successful fabrication of CNT tip. The length of grown CNTs can be well controlled below 1 μm by growth time. The grown CNTs have bamboo-like structure with a catalyst attached on the top, as confirmed by transmission electron microscopy (TEM). Demonstrative observation of graphite surface on an atomistic scale is performed by the fabricated CNT tips. [DOI: 10.1380/ejssnt.2006.276]

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Based on the all-atom empirical force field model, we investigated the force distance curves and the corresponding atomic force microscopy (AFM) images for the single collagen molecule adsorbed on the graphite surface, both in UHV and in water, assuming the (10,0) capped carbon nanotube tip. We found that in UHV the height difference between the proline and glycine amino residues can be clearly resolved in the images, whether the molecule assumes the triple helix structure or its deformed structure which is energetically more favorable. In water, the amplitude of the oscillatory solvation force is found to be different between on top of the collagen molecule and on top of the graphite surface. It indicates that the collagen molecule would be observed to be lower in water than the molecule observed in UHV environment. [DOI: 10.1380/ejssnt.2006.294]

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Electron transport through molecular bridges connecting nano-scale electrodes is investigated theoretically with the coupling effect of an electron with molecular vibrations in the bridge. The ground state of the bridge molecule changes from a polaron state to an undressed state with the increase of the transfer integral. The electronic excited states in the bridge are also determined. Transition probabilities between these states are estimated by the golden rule including the excitation of molecular vibrations. By solving the master equation with these transition probabilities, we simulate the electron transfer process in the molecular bridge. [DOI: 10.1380/ejssnt.2006.311]

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The results of investigations devoted to a search of conditions of the simultaneous metal and semiconductor silicides formation being important problem for microelectronics are presented in the paper. The Si(111)-Fe and Si(111)-Cr systems having been chosen due to low lattice misfit of silicides observed in they were studied by the methods of Differential Reflection Spectroscopy (DRS) and Atomic Force Microscopy (AFM). The new method (Restored Standard method) having been invented for DRS studying of solid phase epitaxy (SPE) in these systems is first noted. The detailed description of processes occurred in the investigated systems and optimal conditions for the simultaneous metal and semiconductor silicides formation are presented in paper. [DOI: 10.1380/ejssnt.2006.319]

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Ni, Co and Fe nanowires were synthesized into nanoporous polycarbonate films to investigate the growth rates and the crystal structures. A polycarbonate membrane filter with numerous cylindrical nanopores was used as a template for the nanowires growth. The pore size was as followings: pore-diameter of 150 nm, pore-length of 6000 nm, and pore-density of 10⁸ pore·cm^-2. The nanowires were potentio-statically electrodeposited into the nanopores from an aqueous solution containing metal sulfate and boric acid. At the cathode potential of -1.0 V, the growth rate of Ni and Fe nanowires was around 6 nm·sec^-1, while that of Co nanowires was around 10 nm·sec^-1. The shape of electrodeposited nanowires was perfectly transferred from that of nanopores and the aspect ratio reached to almost 40. The each nanowire was consisted of single crystalline metal and the long-axis directions of each nanowire were fcc-Ni [111], hcp-Co [001] and bcc-Fe [210]. Basis on the shape anisotropy of nanowires, the magnetization easy-axis oriented to the longitudinal direction of nanowires, which corresponds to the perpendicular direction to the polycarbonate film plane. [DOI: 10.1380/ejssnt.2006.334]

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Epitaxial growth of iron on Cu(001) below 11 ML shows a perpendicular magnetic anisotropy. The sub-monolayer Cr adsorbed fct Fe/Cu(001) have been investigated by x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) to understand the element specific magnetic properties and the electronic states. It is found that the XMCD signal has been clearly observed in the Cr L_2,3 edge, which indicates the anti-parallel magnetic moment in the adsorbed Cr atom to that of the Fe layer. The smaller remnant magnetization for the larger amount of Cr has been observed for both 2.5 and 7.4 ML Fe films, where their magnetizations disappear upon the 0.4 and 0.2 ML Cr adsorption at 185 K, respectively. This behavior is turned out to be caused by the suppression of the Curie temperature. It is also found that the modification of the magnetic property for 7.4 ML Fe is similar to that for 2.5 ML. [DOI: 10.1380/ejssnt.2006.345]

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A monitoring technique for molecular beam epitaxial growth of InAs/GaAs(001) nanoislands is presented. With the help of a combination of synchrotron radiation and a two-dimensional X-ray detector, X-ray diffraction intensity mappings in the reciprocal space have been measured during growth at a rate of 9.6 s per frame. This method provides information on strain distribution and height of Stranski-Krastanov islands under the in situ condition. Because the use of X-rays is not hindered by ambient pressure, this technique is suitable for industry-oriented applications such as organometallic vapor-phase epitaxy as well. [DOI: 10.1380/ejssnt.2006.426]

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We investigated the phase transition from a 3 × 3 to √3 × √3 structure on the Sn/Ge(111) surface at 220 K using a reflection high-energy positron diffraction. We measured the rocking curves at 110 K and 293 K under the one-beam condition and along the [11-2] and [10-1] directions. There are no significant changes in the rocking curves at any conditions according to the phase transition. The curves at both temperatures can be explained by ’one-up and two-down’ model for Sn atoms. The result clearly indicates the order-disorder phase transition. [DOI: 10.1380/ejssnt.2006.435]

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The appearance of ferromagnetism in the surface regime of Pd nanoparticles was recently reported [Phys. Rev. Lett. 91, 197201 (2003)]. To experimentally confirm the surface magnetism, the effects of O₂ gas adsorption on the Pd nanoparticles are studied based on the measurements of the coverage and magnetization. The surface ferromagnetism was weakened in the samples fully covered with O₂ gas. However, the ferromagnetic moment remained after the exposure to O₂ gas. This result shows the ferromagnetism existing in the internal regime in addition to the surface magnetism. [DOI: 10.1380/ejssnt.2006.439]

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A novel spectroscopy, low energy electron excited soft X-ray spectroscopy (LEEXS) has been demonstrated in surface analysis of Si(100) crystal surfaces. The adoption of glancing angle as the incident angle as well as take-off angle makes it possible to highly detect the X-ray signal from surface top layers. In addition to the surface sensitivity, the use of the low-energy primary electron (600 eV to 2.6 keV) enables a (nondestructive) detection of light elements on the surface with its high sensitivity that has ever been impossible for similar X-ray spectroscopy with high-energy primary electrons. [DOI: 10.1380/ejssnt.2006.443]

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Anisotropic confinement of excitons in a single GaAs/Al_0.405Ga_0.595As quantum dot (QD) is studied using micro-photoluminescence (micro-PL) measurements. In this study, a low-density GaAs QD sample is prepared by Modified Droplet Epitaxy (MDE). The QDs are anisotropic in shape and relatively large. This low density sample is combined with micro-PL spectroscopy to obtain single QD spectra. From the single GaAs QD micro-PL spectrum-excitation density dependence, an initial blue shift of approximately 100 μeV is seen for the main peak with increasing excitation density, and as the excitation density is further increased, an overall red shift of approximately 200 μeV is seen. A similar red shift is seen for the multi-excitonic lines. The blue shift can be attributed to a repulsive interaction related to the Pauli Exclusion Principle governing the behavior of the electrons and holes which comprise the excitons, and is a manifestation of the one dimensional nature of the linearly-aligned excitons in these QDs. The red shift can be attributed to an attractive Van der Waals interaction between confined excitons, which increases as the exciton density increases. The anisotropic confinement of excitons is probed by the magnetic field, excitation density, and photoluminescence (PL) polarization dependence of the single QD micro-PL spectrum. It is found that the anisotropic confinement, as well as the large QD size, are responsible for this lack of balance between repulsive forces due to the Pauli Exclusion Principle and van der Waals attractive forces. [DOI: 10.1380/ejssnt.2006.446]

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Platinum metal particles having periodic macropores were prepared from close-packed silica spheres and an aqueous solution of hexachloroplatinum (IV) acid. The sizes of platinum macropores were controlled by the size of the silica spheres. [DOI: 10.1380/ejssnt.2006.451]

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The dopant type and carrier concentration in a patterned semiconductor sample with three different doping regions were measured by scanning nonlinear dielectric microscope (SNDM). SNDM is used in the way of a scanning capacitance microscopy (SCM) with a new detection mechanism based on frequency detection. The topographic, pn-distribution and the carrier concentration images of a patterned semiconductor sample were measured at the same time. In concurrence with a demonstration of the SNDM-SCM measurements, the influence of an adsorbed water layer on measurements is evaluated in the vacuum and in the air over a relative humidity (RH) range of 20 to 80%. Adverse affects on capacitance measurements due to the variation in RH are revealed. [DOI: 10.1380/ejssnt.2006.454]

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A numerical solution of the Nernst-Planck-Poisson (NPP) problem is presented in the paper. The driving forces are the concentration gradients and the electric field. The NPP equations are discretized in space and time and the resulting set of difference equations is solved numerically using the Rosenbrock method in Mathcad 12. The NPP model is used for simulations of transient potential responses to a step current perturbation. This allows for determining impedance spectra of nano- and meso-scale films (L= 10^-8, 10^-7 or 10^-6 m) contacted with permselective electrodes (blocking for anions). Simulated complex impedances exhibit different features depending on interface kinetics. The Warburg type spectrum has been obtained only for L= 10^-6 m and relatively high interfacial kinetics. The present numerical method allows for the direct relating between transport properties of the bulk and the interfaces (ionic diffusivities and heterogeneous rate constants) and complex impedances of electrochemical systems. [DOI: 10.1380/ejssnt.2006.464]

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In order to theoretically examine electrical transport, including the effects of semi-core orbitals, we propose a submatrix inversion approach within the framework of Green's function method. The efficiency and reliability of the proposed approach is investigated for a model system of a Au₆ linear chain between Au(001) surfaces using the BPW91 functional and a modified LANL2MB basis set. For the energy integration of Green's function, the large integral window ranging from -116 eV to E_F (= -5.0 eV) is successfully converted into three small windows [-116 eV, -106 eV], [-67 eV, -55 eV], and [-15 eV, E_F]. The computation time of the submatrix inversion approach is faster by about 40% than that for the full-matrix inversion. At the same time, excellent agreement of the computational results between the submatrix and full-matrix inversion is achieved. Further, we propose a new quantity that is useful to determine an appropriate submatrix size. [DOI: 10.1380/ejssnt.2006.484]

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We deposited a submonolayer of potassium on stepped (755)[=6(111)×(100)] surfaces of copper and nickel in order to fabricate one-dimensional (1D) atomic-chain structures. Upon deposition of 0.09-ML potassium, we obtained 1D atomic chains on Ni(755) but not on Cu(755) as revealed from the low-energy-electron-diffraction(LEED) patterns. The difference in potassium structure has been attributed to the difference in interaction of potassium adsorbates with terraces and steps of the substrates. [DOI: 10.1380/ejssnt.2006.494]

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In this work we investigate the possibility to prepare Pd/SnO₂ systems by impregnating magnetron sputtered tin oxide layers with palladium using Pd(acac)₂ precursor. XRD studies show that as deposited layers are nano-crystalline exhibiting a lack of oxygen. The annealing in oxygen leads to the formation of polycrystalline nearly stoichiometric SnO₂ films. High resolution SEM shows that palladium deposition results in a formation of Pd nanosized particles interacting with the SnO₂ surface. XPS analysis proofs that strong metal-substrate interaction is responsible for a partial formation of the SnO surface phase even in the case of the oxygen annealed Pd/SnO₂ system. [DOI: 10.1380/ejssnt.2006.497]

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Electronic conduction in an atomic sheet is examined theoretically from first principles as an example of a typical two-dimensional system. The conductance per atomic chain, calculated assuming a bias voltage of 0.1 V, is 0.87 G₀ for the atomic sheet, which is lower than for the corresponding single chain (1.0 G₀; G₀ = 2e²/h). The difference is attributed to a reduction of the local density of states around the Fermi level, particularly in the region where the bridge comes into contact with the electrode. [DOI: 10.1380/ejssnt.2006.507]

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Structures of Si(001) surfaces in the initial oxidation processes at 110 K have been investigated by reflection high-energy positron diffraction (RHEPD). From the analyses of RHEPD rocking curves for various coverages of oxygen, it is found that the adsorbed oxygen atoms are located on top of the silicon dimer layer and in the dimer back-bonds. The distance between the surface oxygen and the dimer silicon, between the dimer silicon and the back-bond oxygen and between the back-bond oxygen and the bulk silicon is determined to be approximately 1.0 Å, 0.7 Å and 0.7 Å, respectively. The initial oxidation process is discussed from the change of specular spot intensity due to exposing oxygen. [DOI: 10.1380/ejssnt.2006.510]

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A series of amphiphilic block copolymers containing poly[oligo(ethylene glycol) methacrylate] segments and the corresponding poly[methyl ethers of oligo(ethylene glycol) methacrylate] block copolymer surfaces are investigated by using sum-frequency generation (SFG) vibrational spectroscopy. The terminal moiety on the oligo(ethylene glycol) side chain played an important role in determining the surface structure of the block copolymer films. Due to the amphiphilic character of the methoxy oligo(ethylene glycol) side chain, the PME3MA block exposes the terminal methyl group to the surface and reduces the surface tension in air or vacuum, and it is possible that configurational entropy may also favor the presence of side chains at the surface. The molecular orientation of the block copolymer at the surface is modified due to the multilayered structures of the block copolymers. [DOI: 10.1380/ejssnt.2006.515]

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H-terminated Si(100) with lateral p⁺-n junction has been imaged with emission electron microscopies as a model system where surface electric field is inhomogeneously distributed. It is clarified that mirror electron microscope has a higher sensitivity to the electric field parallel to the surface, compared to photoemission electron microscopy (PEEM) with either Hg-lamp (UV-PEEM) or synchrotron radiation to emit secondary electrons (SE-PEEM). On the other hand, intensity contrast between p-region and n-region arising from the difference in band bending, i.e., an electric field normal to surface, can be detected by UV-PEEM. It has been found in SE-PEEM that the intensity contrast becomes lost with higher kinetic energies. [DOI: 10.1380/ejssnt.2006.539]

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Further hydrogen adsorption onto the hydrogen-covered W(110)-(1× 1) phase results in the reconstruction of the surface hydrogen layer with a sizable corrugation in one direction. The wave vector for the superstructure is found to be very close to the nesting vector of the Fermi surface. Upon the rearrangement, the characteristic surface phonon anomaly becomes much more pronounced. The further pronounced anomaly can be explained by the modification of the electronic band around the Fermi level, concerted with the imposed superperiodicity. [DOI: 10.1380/ejssnt.2006.548]

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Molecular fluorescence induced by tunneling electrons from a scanning tunneling microscope was investigated for copper phthalocyanine thin films deposited on the highly ordered pyrolytic graphite and the Au(111) substrates. No light emission was observed from the copper phthalocyanine thin films on the highly ordered pyrolytic graphite substrate, on the other hand, the fluorescence of copper phthalocyanine on the Au(111) substrate was observed with plasmon-mediated light emission related to the Au(111) substrate. These results are due to the differences in the charge injection efficiency and surface plasmon resonance mode of two substrates. The obtained fluorescence did not satisfy the quantum cutoff condition, that is, observed photon energy was higher than the energy of injected electrons. [DOI: 10.1380/ejssnt.2006.559]

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SnCl₄ and EDTA-4Na were dissolved in a 2 mol/dm³ CH₃COOH - 2 mol/dm³ CH₃COONa buffer solution, and was adjusted to pH4.1 by adding 2 mol/dm³ CH₃COOH or 2 mol/dm³ CH₃COONa solutions. 100 cm³ of the electrolyte was used. In the stationary state, Sn film was not deposited below 100 mA/cm², and Sn film deposited in the range of 200 to 1000 mA/cm². However, thickness was not obtained 1 μm. In the sonication, electrodeposited film obtained 5 ∼ 20 μm in the range of 200 to 1000 mA/cm². Electrodeposition was carried out smoothly, because the mass transfer accelerated with ultrasonic agitation and Sn ion was supplied to electrode surface. Best conditions of sono-electroplating were 0.10 mol/dm³ SnY, pH 4.0, 298 K and 300 mA/cm². The mass transfer and crystallization processes were most affected with micro-jet and shock wave pressure in the range of 200 ∼ 400 mA/cm². Exchange current density and reaction rate constant in the sonication increased compared with that in the stationary and vibration states. As for this, an electron reaction becomes fast by the micro-jet or shock wave pressure. Reduction became difficult to break out as sonication was with powerful agitation. The deposited film was smooth and dense surface in the sonication compared with that in the stationary states by the shock wave pressure. [DOI: 10.1380/ejssnt.2006.574]

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The reason why previous researchers have repoterd many different atomic structures such as cristobalite, tridymite, and quartz for the thermally grown silicon oxide/silicon interfaces is studied by following the possible interface structures during the oxidation processes using the first-principles calculations. The results show that the cristobalite-like structures can be easily formed from the silicon diamond structure. Proceeding with the oxidation, compressive strains are accumulated in these cristobalite-like regions. To significantly release these accumulated strains, it is considered that the cristobalite-like regions change into less strained tridymite-like structures and finally more relaxed quartz-like structures. If the transformation occurs without lateral ordering, then the transformed interfacial structure does not have any order and should be amorphous. This explanation provides us with a unified understanding of the interfacial atomic structures. [DOI: 10.1380/ejssnt.2006.584]

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