A wide-angle laser-assisted three-dimensional atom probe (3DAP) was developed, with a wide angle (0.75 sr) and short flight distance (110 mm) adopted to enlarge the analysis area of the tip. However, the short flight distance of ions resulted in the degradation of mass resolution. Therefore, flight path compensation was examined to improve the mass resolution in the 3DAP with a flight distance of 110 mm. With geometric compensation based on a simple concentric sphere model, the detected ions could be identified. By the compensation of the flight path for a small inclination on the microchannel plate (MCP) in the direction normal to the tip axis, the isotopes of detected ions were identified and high mass resolution was attained for a very short flight distance. [DOI: 10.1380/ejssnt.2009.35]

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We investigate the stable lateral orientation of the single-walled carbon nanotube (SW-CNT) physically adsorbed onto the graphite substrate surface using molecular mechanics simulation. The system of the (3,3) armchair-type SW-CNT comprised of 198 carbon atoms with a length of 40.3 Å interacting with the rigid graphene sheet is considered. Effect of the initial lateral orientation on the final lateral orientation is discussed. The stability of the initial and the final stable orientations can be explained by analyzing the interaction energy between the SW-CNT and the substrate, as a function of the rotational angle θ and the center position r_c=(x_c,y_c) of the SW-CNT, within the lateral (0001) plane of the graphite substrate. Molecular mechanics simulations for the perfect substrate surface under the condition T=0 give the final stable minima near the initial states, instead of the atomic-scale locking around the global minima. [DOI: 10.1380/ejssnt.2009.48]

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Recently, laser pulses on a three-dimensional atom probe have been used to induce field evaporation. The advantages of laser-pulse atom probes are application to higher resistivity materials such as semiconductors and high mass resolution. Early studies of laser-pulse atom probes were performed with laser pulses of nanosecond duration. All evidence from these early studies and most recent studies using sub-picosecond laser pulses have indicated that the field evaporation of atoms by laser pulses occurred by a thermal pulsing mechanism. On the other hand, some recent experiments with sub-picosecond laser pulses have resulted in the proposal of athermal mechanisms (e.g., optical rectification) of field evaporation. Thus, the mechanism of field evaporation at the apex of a needle specimen by sub-picosecond laser pulses has not yet been established. We report the dependence of field evaporation voltage on the polarization angle of femtosecond laser pulses for metal specimens. [DOI: 10.1380/ejssnt.2009.70]

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By conducting a 1200°C vacuum annealing of a 3C-SiC(111) ultrathin film preformed on a Si(110) surface, we have succeeded in forming a graphene layer on a Si substrate. Raman-scattering spectrum from this surface presents a distinct 2D band, whose deconvolution into four subcomponents indicates that the film mostly consists of a two-layer graphene. The peak position is blue-shifted from that of a free-standing graphene formed by a mechanical exfoliation method, suggesting a compressive stress in the film. [DOI: 10.1380/ejssnt.2009.107]

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We studied the metal-molecular interface of Au--S bonds at the L-cysteine modified gold surface using X-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS). Two kinds of L-cysteine layers, i.e., multi-layer and two-layers, were prepared on gold substrate. The formation of unique chemical bond was found at the sulfur-gold interface. The sulfur 1s core-level energy of two-layered L-cysteine on gold is higher by 8.2 eV than that of multi-layered sample. The large chemical shift was also observed in S K-edge NEXAFS spectra. Such remarkably large chemical shift in the case of two-layers has never been reported for any sulfur compounds. The direction of the S 1s energy shift for Au-S bond is opposite to that for the normal metal sulfides. This means that the electrons are donated from the sulfur atom to the gold substrate, and most likely the sulfur atoms are positively charged at likely [δ⁺] states. We conclude that the strong Au-S bonds that are recently used for the immobilization of molecules are due to the observed specific Au--S bond. [DOI: 10.1380/ejssnt.2009.110]

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We found that gold particles, prepared by reduction of HAuCl₄ with trisodium citric acid in the solutions of weak acidity, with a diameter of about 17 nm have different ratios between unsmooth surfaces and smooth surfaces. Gold particles with a diameter of about 7 nm have the structure in which amorphous coexist with crystalline. This paper put forward that study on synthesis of the gold particles of partial amorphous structure and growth increase of unsmooth surfaces and growth control of smooth surfaces should be the future developing direction. [DOI: 10.1380/ejssnt.2009.134]

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The atomic-scale wear, the formation process of the graphene during the lateral line scan process of the nanoscale tip on the multi-layered graphene substrate is studied by using molecular relaxation method. The nanotip is scanned in line forward (along [1 2 -3 0] direction) and backward under the constant-height mode. Analysis of the effect of the tip height on the relative motion of the nanotip, the 1st graphene layer, and the 2nd graphene layer, reveals the transition from the nanotip state to the graphene tip state. During the nanotip state the mean lateral force <F_x> rapidly increases as the mean loading force <F_z> increases. Here the friction between the tip and the surface occurs. However, during the graphene tip state, <F_x> takes nearly the constant value independent of <F_z>. Here the internal friction among the 1st, the 2nd and the 3rd graphene layers occurs. The marked scan directional dependence and the increase of <F_x> near the graphene edge appears. The irreversible shift of the graphene layer after all the scan processes can explain the mechanism of the elementary process of the atomic-scale wear. [DOI: 10.1380/ejssnt.2009.173]

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Dewetting-induced crystallization from hot trichlorobenzene solutions led to the formation of aligned pentacene microfibers or plates, depending on preparation conditions. Fibers with a length of several hundred micrometer and a width of less than one micrometer can be prepared. Bottom-contact field effect transistors with fibers that were oriented perpendicular to the source and drain electrodes showed carrier mobilities as high as 0.04 cm²/Vs. In comparison, plate-like pentacene gave corrected mobilities of up to 0.2 cm²/Vs. [DOI: 10.1380/ejssnt.2009.568]

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Simple methods of fabricating distinctive carbon nanotube networks with different growth density on the same substrate have been investigated. Special substrates fabricated by drying a tris-1,10-phenanthroline iron complex (ferroin) solution on a silicon substrate were used. The ferroin consisted of 1,10-phenanthroline and iron ions in solution. The dried ferroin solution formed fissure structures with unique shapes and iron particles that acted as catalysts for carbon nanotube growth on the substrates. Thermal chemical vapor deposition in a hydrogen-methane gas system was used to grow the carbon nanotubes. The density of the carbon nanotube networks was low in fissure areas and high in block areas. The results indicate that the dried ferroin solution not only produces distinctive carbon nanotube structures, but also changes the growth density on the same substrate. [DOI: 10.1380/ejssnt.2009.586]

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Transient current behavior through two-site molecular bridge systems is studied using density-matrix calculations in order to clarify the multi-site effects in molecule. It is shown that, as increasing the number of energy-level sites in molecule, the relaxation speed becomes slow and the period of current oscillation increases reflecting the change of electronic states in molecule. Moreover, we found that the intra-molecule quantum electron motion often induces a new oscillation and largely modulates the transient current behavior. This motion is also expected seen as a spike-like vibration in steady-state current when a molecule changes its structure such as by the adsorption and desorption of another molecule. [DOI: 10.1380/ejssnt.2009.606]

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The atomic geometries and electronic band structures of Cu-embedded Ni(110) surfaces were studied theoretically. First principles calculation with spin-resolved local density functional theory was applied to the Ni(110) surface, and one to four Cu-embedded Ni(110) surfaces in the 2×2 surface unit cell. The optimized structures for the Ni(110) surface showed that interlayer spacing between the first and the second layer shrunk 11.1% of the bulk distance, but the second and third layer spacing expanded by 2.9% in agreement with previous studies. For the Cu-embedded surfaces, embedded Cu atoms are 11-14 pm higher than the top Ni atoms, which is about four times larger than the difference of the atomic radii. The detailed band structures and corresponding local density of states (LDOS) were calculated. At the embedded Cu atom sites, the surface LDOS near the Fermi level was reduced in agreement with previous scanning tunneling microscopy observation. In addition, by increasing the number of Cu atoms in the top layer, magnetic moments were decreased near the surface regions. [DOI: 10.1380/ejssnt.2009.681]

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Fluorescence intermittency (blinking) of semiconductor nanocrystals (NCs) is interpreted in terms of single photon-counting at high temporal resolution of tens of kiloframes per second (kfps) by fast imaging on ZnS overcoated CdSe (CdSe/ZnS) NCs. We report herein a characterization method based on the threshold resulting from a double exponential distribution as a function of the photon interval to discriminate between “on” (bright) and “off” (dark) states. Histograms of both the resolved “on” and “off” lengths show that they obey single Poisson distributions with their duration constants, contrary to the conventional power-law distributions. We suggest that this characterization gives us more potential power to elucidate blinking kinetics of single CdSe/ZnS NCs on their physicochemical surroundings. [DOI: 10.1380/ejssnt.2009.701]

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Tin-catalyzed silicon nanowires (SiNWs) are synthesized using the hydrogen radical-assisted deposition method. Numerous metal nanoparticles are fabricated after hydrogen radical pretreatment from metal thin film. Large quantities of SiNWs after formation of metal catalysts are synthesized at various growth conditions, such as varied nanoparticle sizes, growth times and temperatures. Their diameters and lengths depend on the growth time and size of nanoparticles. Voluminous whisker-like crystallized SiNWs are obtained at temperatures above 350°C. [DOI: 10.1380/ejssnt.2009.708]

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In the core-shell type hybridized nanocrystals composed of silver (Ag)-core and polydiacetylene (PDA)-shell, the localized surface plasmon (LSP) from Ag-core disappeared during solid-state polymerization in the coreprecipitation method. From high-energy X-ray photoelectron spectroscopy measured with synchrotron radiation X-ray in SPring-8, it has become apparent that a Ag-core is composed of nano-sized conductive domains. Domain boundaries may cause the reduction of the conduction electron mean free path in a Ag-core, and may be responsible for LSP damping without changing the plasmon frequency. [DOI: 10.1380/ejssnt.2009.711]

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We have measured the conductance of atom-sized contacts of some dilute Al alloys in ultrahigh vacuum at room temperature. Measurements on Al-1.1at%Si, Al-2.8at%Mg, and Al-1.1at%Mg-0.6at%Si show no significant alloying effects: their conductance histograms are substantially the same as that of pure Al and exhibit a first peak corresponding to the single-atom contact of Al. On the other hand, a multicomponent Al alloy, Al-4.2at%Zn-3.6at%Mg-0.7at%Cu-0.01at%Ag (“meso10”), yields a conductance histogram which is totally different from others and shows no single-atom conductance peak of Al. We consider that in this high-strength alloy, the influence of alloying on the conductance would be mechanical rather than electronic. [DOI: 10.1380/ejssnt.2009.741]

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The nanoscale peeling of the graphene sheet is numerically studied by molecular mechanics simulation. In the simulation, a rectangular-shaped monolayer graphene sheet with each side of 38 Å×21 Å, comprised of 310 carbon atoms, is peeled from the rigid graphite surface. The six-membered ring around the center position is lifted. We have first obtained the vertical force-distance curve which reflects the transition of the graphene shape from the surface- to the line-contact during the peeling process. The successive partial peelings of the graphene around the lifting center appear as discrete jumps in the force curve, which induce the arched deformation of the graphene sheet. [DOI: 10.1380/ejssnt.2009.783]

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Molybdenum oxide (MoO_x) thin films were deposited by two different techniques of reactive sputtering and their properties were characterized in order to determinate their usage in gas sensors. For preparing the samples the methods of radio frequency (RF) and direct current (DC) magnetron reactive sputtering were used. The composition and microstructure of the films were studied by X-ray photoelectron spectroscopy (XPS), electron probe microanalyser (EPMA), X-ray diffraction (XRD) and Raman spectroscopy. The films' surface was observed by Scanning electron microscopy (SEM) and EPMA. The research was focused on the sensing behavior of the MoO₃ thin films. In order to do that, films of various thickness were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was used. Applying it can be build high sensitive gas sensor capable to detect changes in the molecular range. These prototype QCM sensing structures with MoO_x sensitive films in as-deposited state and without heating the substrates showed good sensitivity to ammonia at room temperature. They are also being tested for sensitivity to other gases and with future development can be successfully introduced into advanced chemical sensing devices. [DOI: 10.1380/ejssnt.2009.796]

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The photocatalytic degradation of phenol under irradiation with UV light was investigated in aqueous suspension of nano titanium dioxide (TiO₂). The effects of photocatalyst such as TiO₂ (anatase) and TiO₂-P25 and power of UV-lamp along with position on the photocatalytic degradation of phenol have been studied. The degradation kinetics was analyzed by the change in phenol absorbance employing UV-vis spectrometry as a function of irradiation time. The degradation follows first order kinetics. TiO₂-P25 was found to be more reactive than TiO₂ (anatase) which is attributed to small crystalline size. Horizontal position of the lamp was found to be better than vertical position of lamp. The degradation was also enhanced with increased in power of UV lamp. [DOI: 10.1380/ejssnt.2009.804]

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Organic memory-transistor devices were fabricated from pentacene-based organic thin-film transistors (OTFTs) with a fullerene layer. The current-voltage (I-V) characteristics show that the fabricated OTFTs exhibit a unipolar property with p-channel characteristics. The fabricated OTFTs devices exhibit a threshold voltage shift upon the application of positive and negative bias. Under the effect of positive bias, the on state was induced and a ΔV_th = 12.9 V was obtained. Meanwhile, the threshold voltage was reversibly shifted by ΔV_th = 9.1 V under the effect of negative bias and the off state was induced. Upon the effect of bias, the carrier mobility of fabricated OTFTs is almost similar in both on and off states. Pentacene-based OTFTs without a fullerene layer for memory effect was demonstrated for comparison. The memory effect is mainly attributed to the fullerene layer. [DOI: 10.1380/ejssnt.2009.808]

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We report that gold nanoparticles were synthe-sized by reduction of HAuCl₄ using halloysites. The synthe-sized samples were analyzed by a transmission electron microscope. The results show that the gold nanoparticles have strip-like, subcircle, and irregular shape, which are single crystals or polycrystals. Their shaps and sizes are relate to the different halloysites. Reduction of Au³⁺ may be related to the surface dangling bonds of halloysite nanotubes. Our research results show that a simple, room-temperature, and green synthesis of the nanocomposite of halloysite nanotubes and gold nanoparticles are possible. The nanocomposite may have the advantages of both the nanocomposite of halloysite nanotubes and gold nanoparticles, which may be widely applied to physical, chemical and biological field. [DOI: 10.1380/ejssnt.2009.813]

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We investigated two self-organized structures of the L-serine on the Cu(001) surface using LEED and STM at 310 K. The first structure just after L-serine deposition formed as thick line domains with width of about 10 nm in (2 -1, 2 4) periodicity, and the second was observed as thin line domains of one-dimensional structure in (2 1, x y) periodicity (where x and y are any integer). These structures were considered by high-resolution STM images in which a protrusion was discriminated as an adsorbate, and we propose interesting structure models. The former structure consists of L-serine dimers as octameric cluster-like of serine, on the other hand, the latter is formed by two serine rows connected in rotated symmetry with (2 1, x y) periodicity. [DOI: 10.1380/ejssnt.2009.821]

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Molecular dynamics simulations are performed to study the mechanical dissociation pathways of a wheat germ agglutinin (WGA) dimer under the tensile force exerted by the atomic force microscopy (AFM). We found a dissociation pathway in which both monomer units are elongated and their tertial structures are destroyed before the rupture. The force extension (F-E) curves are found to show successive saw-tooth peaks indicating the stepwise destruction of interactions inside monomer structures. In addition, the interactions at their interfaces are found to be destroyed at the largest force peak. At the rupture where the dimer dissociates completely, a small jump is observed in the F-E curve, which amounts to 70 pN. [DOI: 10.1380/ejssnt.2009.825]

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We have obtained the azimuthal angle dependence of the second harmonic (SH) intensity from bimetallic Pt/Cu and Pt/SiO/Cu nanowire arrays. The arrays were fabricated by shadow deposition on NaCl(110) faceted templates. The SH intensity from the Pt/Cu nanowire array measured in S_in/S_out polarization combination were 4.7 times larger than that from the Pt/SiO/Cu nanowire array at the fundamental photon energy of 2.33 eV. Phenomenological analysis of the intensity patterns and numerical calculation of the local fields have shown that the inversion symmetry broken at the metal-metal interface is responsible for the enhanced SH generation from the Pt/Cu bimetallic nanowire arrays. [DOI: 10.1380/ejssnt.2009.831]

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On a Ni (111) surface, a single-layer graphene sheet with a 1 × 1 atomic structure grew up in epitaxial way. Chemical etching the substrate made it possible to separate macroscopic self-standing sheets of graphene a few tenth mm in size, which were characterized by transmission electron microscopy (TEM). [DOI: 10.1380/ejssnt.2009.837]

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Grazing exit micro X-ray fluorescence analysis (GE-μ-XRF) using an X-ray absorber method was applied to an analysis of Pb attached to an aqueous leaf of Cammelia hiemalis. As a result of the analysis, we found that X-rays emitted from the surface region of the leaf could be detected selectively and then X-rays of Pb could be detected with low background using this analytical method. In this research, an effect of the X-ray absorber was indicated by comparing between X-ray spectra gained with and without use of that. However, since Pb was not attached to a leaf analyzed for this comparison, peak/background ratios of the X-rays of Pb using the X-ray absorber were not compared with those without use of the X-ray absorber. Moreover, X-ray exit angles did not correspond with each other between with and without use of that. We, therefore, applied the GE-μ-XRF to an analysis of As attached to a leaf of Cammelia hiemalis, and then investigated the effect of the X-ray absorber at identical X-ray exit angles with and without use of that. As a result of that, we found peak/background ratios of X-ray peaks of As with use of the X-ray absorber drastically increased at grazing exit angles as compared to those without use of that. [DOI: 10.1380/ejssnt.2009.841]

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The flat-band potentials of (0001) face (Ga-face) and (000-1) face (N-face) of free-standing n-type GaN with a carrier concentration of 1× 10¹⁸ cm^-3 are measured by the bias dependence of photoluminescence intensity in electrolyte solution. The flat-band potentials of Ga-face and N-face are —1.5±0.1 V and —1.2±0.1 V in 0.1 molL^-1 Na₂SO₄ solution (pH7) on the basis of Ag/AgCl reference electrode, indicating the conduction band edge of N-face is about 0.3 eV lower than that of Ga-face. This result is consistent with the observation that the H₂ gas generation occurs vigorously on N-face compared with Ga-face when the free-standing n-GaN electrode is at a fixed bias of —1.8 V vs. Ag/AgCl. [DOI: 10.1380/ejssnt.2009.847]

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The adsorption and thermal dissociation of nitric oxide on a stepped Pd(112) surface has been investigated by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). NO undergoes molecular adsorption on a stepped Pd(112) surface at 300 K. With increasing temperature, some NO adsorbed on the surface desorbs molecularly and the remaining NO starts to dissociate into nitrogen and oxygen. The NO dissociation takes place preferentially at the step sites. All NO molecules adsorbed on the surface dissociate above 423 K. Nitrogen desorbs from the surface above 700 K but oxygen exists on the surface or subsurface. UPS results show that the peak at 11.2 eV below Fermi level (E_F), originating from the 1π+5σ orbital of NO adsorbed on step sites of Pd(112), disappear at a lower temperature than does the peak of NO adsorbed on terrace sites. This indicates that NO molecules adsorbed on step sites are dissociated at a temperature lower than those at terrace sites. The dissociation activity of NO on Pd(112) is stronger than on the (111) and (110) surfaces, but weaker than on the (100) surface. The order of the dissociation activity is Pd(100) > Pd(112) > Pd(111) > Pd(110). [DOI: 10.1380/ejssnt.2009.851]

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Spray deposition method was developed as a cost-efficient technique for fabrication of multilayer structures used in the organic based devices (OBD) like diodes, displays and solar cells. The active layers of OBDs were deposited using conventional airbrush. The temperature was varied for layer morphology optimization. The spray deposited at 70°C films showed smoother surface than the spin-coated ones, pinhole-free and uniform coatings were obtained. It was demonstrated that could be produced multilayer structure, containing layers from different organic materials, but all soluble in the same solvent. They remained separated without sublayer damaging. The performance of sprayed multilayer organic device was compared to that of the spin-coated. The structures prepared by spray showed better electrical performance and increasing of the current efficiency. [DOI: 10.1380/ejssnt.2009.859]

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Specimens for three-dimensional atom probe (3DAP) analysis must be needle-shaped and the apex of specimen is primarily fabricated by focused ion beam (FIB). In the specimen preparation by FIB, the gallium ions are generally implanted into the surface region of the specimen during the irradiations of the ions. Therefore, the surface structure of the specimen is disarranged and amorphous. This phenomenon makes it difficult to reconstruct a three-dimensional image of the specimen. The implantation is caused by irradiating the apex of the specimen with FIB. In this study, we propose a new specimen preparation method in which FIB is irradiated from behind the needle specimen due to avoids the implantation of gallium ions. The assembly in this method was installed in the FIB instrument. The specimens were fabricated by means of the conventional and proposed methods and analyzed by atom probe in our laboratory. It was shown that not only the gallium implantation but also the rupture of specimen were inhibited by the proposed method. [DOI: 10.1380/ejssnt.2009.863]

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Fe silicide growth on a Si(111) surface has been characterized by Weissenberg RHEED. The silicides were grown in the present study via two fundamental methods, reactive deposition epitaxy (RDE) and solid phase epitaxy (SPE), with various deposition amounts of Fe. The silicide species and its epitaxial orientation were determined from three-dimensional diffraction patterns obtained using Weissenberg RHEED. It was found that only α-FeSi₂ islands grew by the RDE method. Both α-FeSi₂ and β-FeSi₂ islands grew by the SPE method. The proportion of β-FeSi₂ increased with increasing Fe deposition amount, until only β-FeSi₂ was finally observed. The present results could be explained by the surface or interface reaction model wherein the reaction at the Si surface and at the Fe/Si solid interface caused α-FeSi₂ and β-FeSi₂ growth, respectively. [DOI: 10.1380/ejssnt.2009.866]

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The formations, binding energies and monomer dipole moments of small water cluster systems (H₂O)_n with n = 1-12, have been investigated by the density functional calculations using B3LYP/6-311++(2d,2p) level theory. A new method based on reactivity indices from Fukui functions has been introduced to generate the initial structures. Constant adding one by one water molecule from monomer to the cluster systems (hydration reactions) have transformed the cluster shapes by following formation order: linear (n = 2), cyclic planar (n = 3-6) and 3-dimensional (n = 7-12) ones. The average binding energies of small water cluster systems have converged asymptotically to the intermolecular binding of bulk water, concerning the local binding energy fluctuation effects on the average binding energy trend. Based on total electronic energies, zero point energies and optimized transition structures energies (activation energies) analysis, we have predicted that the cyclic planar is the most stable hexamer formation to compete with the cage and the book ones. Considering the monomer dipole moment calculations with regard to the experimental data references, we have discovered new findings which have not clarified yet before, that the smallest piece of ice water is the cyclic tetramer (n = 4) and the cage hexamer is the smallest stable liquid formation. [DOI: 10.1380/ejssnt.2009.871]

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Cluster ions such as C₆₀⁺ are well used as the sputtering ions for polymer depth profiling. The molecules of analyte surfaces are occasionally damaged by the ion bombardment during sputtering, leading to a loss of the molecular information. In order to obtain a proper polymer depth profile, sputtering conditions shall be optimized, however, they have not been investigated sufficiently. In this study, incident angle dependence was investigated at the angle from 48° to 76° with respect to the surface normal. Samples used were the bulk polycarbonate (PC), bulk polystyrene (PS), and Irganox1010/Irganox3114 organic multi layer film. Irganox3114 layers were deposited at the several depths in the Irganox1010 film as markers to evaluate the interface resolution. Characteristic TOF-SIMS spectra from PC and PS were retained even after sputtering hundreds of nanometers at 76°, although the loss of the molecular information due to carbon deposition and/or damage accumulation was observed at 48°. From the depth profile of Irganox1010/Irganox3114, significant improvement of interface resolution was obtained at 76° over that at 48°. This work indicates that glancing angle sputtering clearly becomes one of the approaches to optimize C₆₀ polymer depth profiling. [DOI: 10.1380/ejssnt.2009.878]

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We have developed a photoemission-assisted plasma-enhanced chemical vapor deposition (CVD) process, where DC discharge plasma is assisted by photoelectrons emitted from the substrate under ultraviolet (UV) light irradiation. Under Ar gas atmosphere and in vacuum, plasma current was measured as a function of sample bias voltage to clarify the mechanism, by which photoemission-assisted plasma is generated. Owing to the advantages of the photoemission-assisted plasma-enhanced CVD, where the plasma is generated close to the substrate and in a controllable volume, we have succeeded in growing shiny black films of networked nanographite, without any catalyst, on Si(001) and SiO₂(350 nm)/Si(001) substrates at a deposition rate of ∼2 μm/min despite of low electric power consumption of plasma, ∼4 W. Cross-sectional transmission electron microscopy (TEM) and diffraction (TED) observations revealed that samples grown at ∼700°C with Ar-diluted CH₄ were composed of multilayer graphene particles (diameter of ∼10 nm) that were closely connected to each other and shared some graphene sheets between them, although their crystallographic configurations were randomly oriented. In bulk-sensitive C 1s photoelectron spectra using synchrotron radiation at 7933 eV, a chemically-shifted component of sp²-bonded carbon atom was dominant and the π—π^* transition loss peak was clearly observed for the samples grown on both substrates, indicating that the multilayer graphene particles substantially contain high-quality graphene sheets in agreement with evaluations by microscopic Raman spectroscopy. We named the layered carbon structure “carbon mille-feuille.” [DOI: 10.1380/ejssnt.2009.882]

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We have measured the break voltage of the 1G₀ contact of Au, Ag, Cu, and AuAg alloys at room temperature in ultrahigh vacuum. Exploiting the break junction technique, we produced a 1G₀ contact and broke it by applying a voltage ramp. The break voltage of each metal exhibits a broad distribution, and the average break voltage decreases as Au >Cu ≥ Ag, in consistent with the elemental dependence of the high-bias stability of the 1G₀ contact suggested in previous experimental studies. In AuAg alloys, the break-voltage distribution for some alloys exhibits a double-peak structure, each peak locating close to the break voltage of the 1G₀ contact of pure Au and Ag, respectively. This observation suggests that the break voltage of AuAg alloys is locally determined by the elemental species of the atom occupying the contact site. [DOI: 10.1380/ejssnt.2009.891]

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Partial oxidation reaction of methanol has been investigated on Cu/MnO thin films grown on Ni (100) surface in an ultra high vacuum (UHV) system combined with a reaction cell. The partial oxidation reaction of methanol proceeds on the Cu/MnO surfaces with Cu films thicker than 1.5 ML at a lower temperature of 470 K, in consistent with the activity of copper manganese oxide catalysts prepared by co-precipitation method. Post-reaction surface analysis by 2p X-ray photoelectron spectroscopy (XPS) and LMM Auger electron spectroscopy (AES) of Cu and Mn have demonstrated that Cu⁺ species exist as Cu₂O overlayers which are stabilized by MnO underlayers acting as a template during the reaction. It is proposed that partial oxidation reaction of methanol proceeds through surface formate destabilized on the Cu₂O overlayers at lower temperatures. [DOI: 10.1380/ejssnt.2009.898]

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The surface structure change of sapphire A-face (1 1 —2 0) by heating in air has been investigated from the viewpoint of its influence on the aligned growth of single wall carbon nanotubes (SWCNTs). The step shape was getting regular with an increase of the annealing temperature, and straight step array appeared at 1473 K. A further increase of the temperature to 1523 K resulted in altered region formation on terraces, although the atomic step shape was not changed. A terrace appeared as if it had been divided into two sub-terraces, but the height difference was less than 0.1 nm. Secondary electron images showed different contrasts in two regions, suggesting a compositional difference between them. Aligned SWCNTs were obtained regardless of the annealing temperature up to 1473 K. However, on the 1523 K-annealed surface, SWCNTs grew irregularly. The altered region changed the interaction between SWCNTs and the surface. [DOI: 10.1380/ejssnt.2009.904]

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We report first results about the ability of low density amorphous ice nanolayers to behave as a “matrix” and trap monomeric neutral glycine molecules at 125 K, a temperature much greater than the commonly used liquid He temperature region. FTIR-RAS spectra of those monomeric neutral glycine molecules adsorbed on low dense amorphous ice were obtained for the first time and indicate that glycine adsorbs molecularly with the carboxylic group and the nitrogen atom hydrogen-bonded to the ice surface. [DOI: 10.1380/ejssnt.2009.693]

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The electronic structure of Ni₂P(0001) has been investigated by photoelectron spectroscopy utilizing synchrotron radiation. In the valence band spectra, a Ni 3d—P 3p hybrid band (main band) and a satellite were observed at 0-4 eV and at 8 eV, respectively. The satellite showed a resonant behavior around the Ni 3p threshold, and is associated with the photoemission leading to the two-hole bound final state. From the analysis of the anti-resonance dip of the main band intensity, the Ni 3d component was proved to be included in the whole binding energy region of the main band. In the P 2p core-level spectra, the surface-shifted 2p levels were resolved from the bulk 2p levels, while the surface-shifted peaks were not found in Ni 3p spectra. The binding energies of the surface-shifted P 2p levels were lower than those of the bulk components by ∼1 eV. The surface-shifted levels were attributed to the 2p levels of the surface P atoms which take on a six-fold coordination. [DOI: 10.1380/ejssnt.2009.1]

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The co-adsorption of titanium atoms and oxygen molecule on the Ag(100) cluster surface has been investigated by the density functional theory calculation. In order to achieve the convergence of a self-consistent-field (SCF) iteration, the approach using the pseudo-fractional occupation number (pFON) or the quadratically convergent SCF (QCSCF) approach is employed in this study. First, we investigated the adsorption of nTi atoms (n = 1-4) on Ag(100), and found that any bonding orbitals between Ti and Ag atoms were not formed and the systems were stabilized by the formation of Ti—Ti bonds. As the Ti-precovered surfaces were interacted with O₂, we found that oxygen adsorbs both molecularly and dissociatively at n ≤ 2, while the adsorbed oxygen always dissociates at n ≥ 3. At n ≥ 3, the dissociated O atoms form a TiO-chain or a TiO-cyclic unit. We also revealed that the formation of Ti—O—Ti bond is essential for the stabilization of O₂/nTi/Ag(100) systems. [DOI: 10.1380/ejssnt.2009.7]

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We perform fully-relativistic first-principles calculations on Bi{012}films which are stable when the film thickness is very small. We find that the 2ML free-standing film has bistability, i,e, the two top atoms are buckled in one geometry and they are nearly flat in the other geometry. The calculated amplitude of the buckling in the buckled structures is 0.17 Å whereas the amplitude is 0.41 Å when the spin-orbit interaction (SOI) is not included in the calculation. Furthermore, the bond lengths between the top and the second top atoms in the buckled structure are alternant when the SOI is included in the calculation. Therefore, the SOI has a significant effect on the geometry. The total energy difference between the two structures is less than 1 meV. Therefore, we expect that one of the two structures appears depending on circumstance such as the interaction between the substrate and the film. [DOI: 10.1380/ejssnt.2009.13]

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We have theoretically analyzed electron transport in a Si atom wire at a finite bias voltage using a first principles method. Electronic states and transport properties are calculated using the Lippmann-Schwinger equation using the Laue representation in the framework of the density functional theory. We analyzed the transport properties of the Si wires between the metallic electrodes, and elucidated the effects of metallic contacts on Si atom wire, the character of conduction channels, and the dependence on the bias voltage. The conduction channels are analyzed using eigen channel decompositions and then it is found that the three channels contributing to the transport are open in the bias window under the finite bias voltage. [DOI: 10.1380/ejssnt.2009.17]

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A secondary-ion mass spectroscopic study of a wurtzite GaN(0001) surface was conducted to test the operation of a novel surface-chemical analyzer using Ar³⁺ (7.5 keV) and Ar⁴⁺ (10 keV) ions. The analyzer allows us to measure the time of flight of a secondary ion simultaneously with the detection of the backscattered atom or ion that captured electrons from the surface atoms. A proton, C_mH_n⁺ (m = 1—6 and n = 0—13), N⁺, Ga⁺, and GaN⁺ ions were observed in the mass spectrum. The spectral width and profile were different between Ar⁰ and Ar⁺ -coincidence measurements. [DOI: 10.1380/ejssnt.2009.21]

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ZnO nanowires were synthesized by the heat treatment of ZnS substrates with Ga droplets in the air, and their morphological and structural properties were then investigated. The nano-sized ZnO wires were formed on thin ZnO layers accompanied with the formation of ZnGa₂O₄. It was found that the growth direction of the nanowires is ZnO[0001], and which is parallel to ZnGa₂O₄[010]. The growth mechanism of the ZnO nanowires is discussed based on the thermal stability or enthalpy of formation of the oxides. [DOI: 10.1380/ejssnt.2009.25]

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The growth mode of graphene epitaxially grown on vicinal SiC(0001) substrates as well as on-axis SiC(0001) surface has been investigated by scanning tunneling microscopy and low energy electron diffraction. The results show that the graphene favors to start to emerge from the edge of the surface steps, forming narrow graphene domains at the step edges on the vicinal surface with 4° off-axis angle, well separated by carbon rich (6√3×6√3) domains, suggesting the possibility of obtaining graphene nano-ribbons. The graphene film grown on vicinal surface with larger off-axis angle (21°) shows a wave-like morphology, exhibiting the continuity of graphene film across the step edges. [DOI: 10.1380/ejssnt.2009.29]

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We present a lattice model to study the “decoration” with the adsorbates on the stepped surface together with the step bunching induced by adsorbates. The model is the modified restricted solid-on-solid model coupled with Ising system (mRSOS-I model), where the energy reduction of the lateral bonds between the adsorbates on the different height of the surfaces is taken into consideration. We show, by Monte Carlo method, that the reduction factor ζ is one of the key parameter for the decoration on the stepped surface in addition to another key parameter of the interplay factor α, which we previously introduced in the original RSOS-I model. The deposited islands appear from the down side, the upper side, or the both sides of the steps depending on the values of ζ and α. [DOI: 10.1380/ejssnt.2009.39]

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The Debye-Waller factors obtained by EXAFS analysis of the trigonal Te (t-Te) and the Te nanoparticles are analyzed by a Debye model. In t-Te the Debye temperature (Θ_D) of the intrachain interactions is about two times higher than that of the interchain atomic interactions. The Θ_D for the intrachain interactions of the Te nanoparticles is higher than that of t-Te, but Θ_D for the interchain interactions of the Te nanoparticles is lower than that of t-Te. The reduction of the interchain interactions for the Te nanoparticles would induce the change of the Debye temperatures. [DOI: 10.1380/ejssnt.2009.45]

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We have developed a mechanically controllable break junction (MCBJ) system in ultra high vacuum (UHV). The Au atomic contact in a hydrogen environment was investigated using this newly developed system. The conductance of the Au atomic contact decreased with the introduction of hydrogen gas. The vibration spectra showed symmetric peaks around ±50 meV, which could be assigned to the vibration mode between Au and hydrogen. The conductance and vibration spectroscopy measurement suggested that the hydrogen atom or molecule would adsorb on or incorporate into the Au atomic contact. [DOI: 10.1380/ejssnt.2009.53]

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The free-electron-like surface-derived electronic state in Al(100) has been examined in detail by high-resolution angle-resolved photoemission spectroscopy (ARPES). We observed a kink structure in the energy band-dispersion at the energy of ∼ -40 meV, which is derived from the electron-phonon interaction. Based on the quantitative analyses of the ARPES line shapes, we have obtained the imaginary and real parts of the self-energy. The electron-phonon coupling parameter has been evaluated to be λ_el-ph = 0.67, which is much larger than the electron-electron coupling parameter λ_el-el = 0.06. [DOI: 10.1380/ejssnt.2009.57]

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The electron diffusion length is directly evaluated from the dependence of photocurrent on the position of dye-adsorption front using the structure of selectively dye-adsorbed solar cell. By changing the thickness of the region without dye-adsorption, the thickness that the photocurrent starts to flow is defined as the electron diffusion length in nano-porous TiO₂ layer. This method is applied to investigate the effects of the electrolyte solvent and the annealing temperature on the electron diffusion length in nano-porous TiO₂ layer. It is suggested that viscosity and molecular size of solvent affects the diffusion of electron in TiO₂ nano-porous layer from the results that the electron diffusion length is 1.6 times longer in aprotic acetonitrile solvent than in protic ethylene glycol solvent. At 600°C annealing, the electron diffusion length shows the maximum of 27 ± 1 μm in LiI/I₂/acetonitlire at the incident photon flux of 2.2 × 10¹⁵ cm^-2 s^-1 at 540 nm. [DOI: 10.1380/ejssnt.2009.61]

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We have studied the structural and chemical changes of Rh on Al₂O₃/NiAl(100) depending upon heat treatment, and the oxidation reaction of atomic sulfur on Rh/Al₂O₃/NiAl(100) surface under atmospheric environment by means of Near Edge X-ray Absorption Fine Structure, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy techniques. Rh nanoclusters are formed on the Al₂O₃/NiAl(100) surface after the deposition of Rh. With elevated temperature, the aggregation of Rh atoms occurs on the Al₂O₃ layer at 600 K. At the temperature range from 600 to 1000 K, Rh atoms diffuse and dissolve into the NiAl(100) substrate through Al₂O₃ layer. On the other hand, the S 2p XPS and S K-edge NEXAFS studies indicates the noticeable oxidation of the atomic sulfur adsorbed on Rh/Al₂O₃/NiAl(100) under atmospheric environment. In this oxidation reaction, not only the reaction temperature but also the degree of O₂ partial pressure seems to be important. [DOI: 10.1380/ejssnt.2009.65]

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