Zn doped strontium germanate has been prepared by the hydrothermal method using strontium acetate, germanium dioxide and zinc acetate as the raw materials. The Zn doped strontium germanate were analyzed by X-ray diffraction, scanning electron microscopy and solid UV-vis diffuse reflectance spectrum. The structures of Zn doped strontium germanate were confirmed to be hexagonal SrGeO₃ and rhombohedral ZnGeO₃ phases. The band gap of Zn doped strontium germante decreases from 3.67 eV to 2.88 eV with the change of the Zn doping mass percentage. The photocatalytic activity of the Zn doped strontium germanate has been evaluated for the photocatalytic degradation of gentian violet under UV light irradiation. The results reveal that the Zn doped strontium germanate has the enhanced photocatalytic activity. [DOI: 10.1380/ejssnt.2015.8]

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The increasing importance of the volume expansion effect on crystalline materials induced by ion-beam irradiation has drawn much attention because of its applications. For example, the expansion effect is used as a good probe to investigate any crystalline-amorphous (c-a) phase change and/or damage. Because the expansion rate and its depth profile can be controlled by means of the irradiation parameters, such as fluence and energy, the deformation of structures on the micro-/nano-meter scale is expected. The fluence needed to achieve deformation is relatively low, and it is expected that irradiation-induced damage is reduced compared with that induced by conventional ion-beam fabrication. Therefore, this expansion effect is a potential method to improve the ion-beam technology employed to fabricate complicated 3-dimensional structures requested in actively developing industrial fields, such as MEMS/NEMS. [DOI: 10.1380/ejssnt.2014.35]

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We study the electronic transport properties of armchair graphene nanoribbons with a width of up to 12 nm bridged between two Au electrodes using first-principles calculations. The transport properties sensitively depend on the ribbon width, even though the width reaches 12 nm. The variation of transport properties is ascribed to the detailed electronic structures of graphene ribbons, which sensitively depend on their width. The band structure and the symmetry of π state of the graphene play important roles in determining the transport properties. [DOI: 10.1380/ejssnt.2015.54]

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We investigated the relationship among the number of flash annealing times to obtain Si clean surface and the change of arsenic dopant concentration and subband levels using secondary ion mass spectroscopy (SIMS) and angle-resolved photoelectron spectroscopy(ARPES). The SIMS result shows that the first five times of the flash annealing already induces significant reduction of the dopant concentration in agreement with the recent work [Pitter et al., J. Vac. Sci. Technol. B 30, 021806 (2012)]. We found the energies of hole subband levels rapidly decrease as the number of the flash annealing times increases. We calculated the subband levels in a broadened confinement potential taking the dopant reduction determined by SIMS into account. The energy separations of the calculated subband levels were in good agreement with the ARPES results. [DOI: 10.1380/ejssnt.2015.75]

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Pure cubic zirconia (c-ZrO₂) is unstable at room temperature. We achieved the epitaxial formation of c-ZrO₂ crystalline surface oxide islands on ZrB₂(0001) by annealing the substrate without sample cleaning at 950°C under ultrahigh-vacuum conditions. The interface structure at the c-ZrO₂ islands and the ZrB₂(0001) substrate was investigated using element-specific circularly-polarized-light photoelectron diffraction, angle-resolved X-ray photoelectron spectroscopy, and reflection high-energy electron diffraction (RHEED). The ZrO₂(111) islands was a twin crystal oriented in ZrO₂[1 -1 0]//ZrB₂[2 -1 -1 0], and was stable up to around 1500°C. The Zr-Zr distance of ZrB₂ bulk and that of ZrO₂(111) agree with at the ratio of 8 to 7. [DOI: 10.1380/ejssnt.2015.111]

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We investigate laser-assisted field emission (LAFE) from a silicene nanoribbon (SiNR) using time-dependent density functional theory (TDDFT) simulation. The emission mechanism in the present study is considered to be over-barrier photoemission and is found to be governed by electronic dipole transitions, the characteristics of the excited states, and the energy levels of the excited states relative to the potential hump. The qualitative features of emission from the SiNR are similar to those from graphene nanoribbons (GNRs). The emission currents from SiNR, however, are found to be much larger than those from GNR for the same laser parameters in spite of a larger work function for SiNR. We reveal the emission currents in real time and space on an atomic scale, and observed current being driven back and forth in the early stage of emission. We further elucidate the dynamical correlation among the laser pulse, the Kohn-Sham potential and emission currents wiggling under the ponderomotive force. [DOI: 10.1380/ejssnt.2015.115]

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We report the point contact visible luminescence from Ga-doped ZnO layers. The Ga-doped ZnO layers were grown by the thermal oxidation of ZnS substrates with gallium in the air. The injected light emission was observed around the point-contact surface of ZnO layers when a forward DC voltage in the range of 2.5-9.8 V was applied (point contact was positive). Typically, we illustrated the luminescent spectrum for 6.7 V which showed a wide emission band centering at 680 nm. [DOI: 10.1380/ejssnt.2015.201]

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In this study, the photodepostion of metallic silver was examined by immersing strontium-doped sodium tantalate photocatalysts in aqueous AgNO₃ solution. When Ta⁵⁺ was doped with Sr²⁺ through a solid-state reaction, the observed photodeposition rate was enhanced by five times relative to that exhibited by undoped NaTaO₃. This ehancement was possibly due to restricted electron–hole recombination caused by the doping. On the other hand, when Na⁺ was doped with Sr²⁺ through a hydrothermal reaction, only slight enhancement in the photodepositon rate was observed. [DOI: 10.1380/ejssnt.2015.253]

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A simple probe that is applicable as an electric contact to nm-thick films and 2D films such as graphene and MoS₂ without destroying the specimen has been developed. The concept of the development of the probe is based on the repulsive region used in atomic force microscopy technique but without any precise feedback. The robust electric contact with the probe has been demonstrated by biased XPS measurement of a MOS specimen and by resistivity measurement of a 5-layer graphene film on sapphire. It has also proved that there was no detectable damage or contaminations on the specimens after the measurements. [DOI: 10.1380/ejssnt.2015.307]

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To investigate the electronic state of Zirconium diboride (ZrB₂) (0001) clean surface, we measured two-dimensional photoelectron intensity angular distribution (PIAD) patterns with a display-type spherical mirror analyzer (DIANA). As a result, we obtained two-dimensional band dispersion cross section patterns of ZrB₂. In these patterns, we observed the transition-matrix-element effect of linearly-polarized light excitation. Comparing the experimental data to the calculation results, we concluded that the band at the K point at a binding energy of 3.4 eV consists of B 2p_z, Zr 4d_yz, and Zr 4d_zx orbitals. This suggests that this band is the bonding state between the B layer and the Zr layer. We confirmed that this hybrid orbital, where the d electrons of Zr are donated to the p_z orbital of B, makes the Dirac-cone-like band of ZrB₂. [DOI: 10.1380/ejssnt.2015.324]

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We investigated the lattice matching condition of two-dimensional (2D) lattices based on the group isomorphism of 2D Euclidean space to complex plane. This isomorphism enables us to avoid the inconvenience derived from the algebraic structure of 2D vectors and provides the systematic analysis. We found that the lattice matching is closely connected with ideal class group which is an invariant in the algebraic number field. We also provide an algorithm to construct a structure model for a superstructure formed by overlapping two 2D lattices, which is helpful for making trial models in the structure analysis. [DOI: 10.1380/ejssnt.2015.361]

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Reduced graphene oxide coated SiO₂/Si substrates were obtained by wet-chemical reduction of graphene oxide for the use as semiconductor material in field-effect transistors. The morphological and chemical characterization was done by using SEM, Raman spectroscopy and XPS. Raman and XPS measurements can characterize the success of the graphene-oxide reduction, but only for small parts spots of the surface (e.g. 0.41 μm² laser spot size with Raman). In order to evaluate larger surface areas and the electrochemical activity of the graphene oxide and reduced graphene oxide, additional spectroscopic measurements using the SECM were performed. The samples coated with unreduced graphene oxide showed no electrochemical activity, while reduced graphene oxide samples showed conducting properties. Further information about the topology of the surface was obtained by applying the SECM constant distance mode. The degree of graphene coverage was calculated from SECM data and compared to the coverage obtained by SEM. It was found that 68±7% coverage is sufficient to ensure electronic contact between the Source and Drain electrodes (resistance less than 1 kΩ). Functionality of the fabricated field effect transistors was demonstrated by titration of pH solutions and characterization of the characteristic curves. [DOI: 10.1380/ejssnt.2015.366]

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A theory is derived for localized plasmons in multiple metal nanostructures by developing the theory of localized bulk and surface plasmons for metal nanostructures in the random phase approximation (RPA) at the high frequency condition. The local electron density in multiple metal nanostructures is expressed as the sum of the electron density of each metal nanostructure. Self-consistent integral equations derived in the RPA give determinants to calculate the localized surface plasmon frequencies for multiple metal nanospheres with step-function-like electron density at their surfaces. The frequencies are analytically calculated in the dipole approximation for a dimer and chain of metal nanospheres. The frequencies are red- or blue-shifted depending on the spacing between the metal nanospheres. A light emission formula is also derived for multiple metal nanostructures in the dipole approximation. The light emission intensities from the dimer and chain are analytically calculated using the step-function-like electron density model. The retardation effect on the localized plasmons for multiple metal nanostructures is then investigated by applying the structural Green's function method, which is used to calculate the electronic structures of condensed matter. [DOI: 10.1380/ejssnt.2015.391]

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Chemical vapor deposition (CVD) is a promising method to produce large-size single-crystal graphene, and further increase in domain size is desirable for electro/optic applications. Here we studied the effect of low amount of air introduction by intentional leak on graphene growth in atmospheric pressure CVD. The air introduction at the heating process resulted in roughening of Cu surface induced by oxygen, while air introduction at the annealing under H₂ ambient drastically decreased graphene density due to reduction of active sites for graphene nucleation both by surface oxidation and enlargement of Cu domain. Although air introduction only at the growth stage was ineffective for graphene nucleation, air introduction for both annealing and growth provided great enhancement of domain growth without increasing the density of graphene, which is an optimized condition to obtain a large single-crystal. This controlled introduction of air in atmospheric pressure CVD provided ∼ 2.5 mm hexagonal single layer graphene with high quality. [DOI: 10.1380/ejssnt.2015.404]

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The surface modification of tourmaline powder with methacrylic anhydride was studied in this work, and the reaction process conditions were optimized according to the experimental parameters of contact angle and turbidity in liquid paraffin. The structure of the modified tourmaline was characterized by means of IR, XRD and SEM. The structural analysis indicated that methacrylic group was attached onto the surface of tourmaline by the reaction of tourmaline with methacrylic anhydride to get a polymerizable tourmaline methacrylate. The experimental results indicated that modified tourmaline presented enhanced hydrophobicity than the unmodified tourmaline. [DOI: 10.1380/ejssnt.2015.422]

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We have synthesized stable gold nanoparticles (AuNPs) by a simple ultrasonic irradiation in water/alcohol binary solutions without additive stabilizer agents. Methanol, ethanol, and 1-propanol are used as solvents. The morphology and optical properties of the sonochemically synthesized AuNPs are characterized using SEM and UV-vis spectroscopy. The average particle diameter of as-prepared AuNPs was 36 ± 10 nm for water/methanol system (methanol: 25 vol%), 56 ± 17 nm for water/ethanol system (ethanol: 35 vol%), and 24 ± 7 nm for water/1-propanol system (1-propanol: 35 vol%). The water/1-propanol system give the smallest average particle diameter together with the narrowest particle size distribution. This fact also support that the hydrophobicity of 1-propanol is higher, because the side chain of 1-propanol is longer than those in the other alcohols. Thus, it can be concluded that the dispersion of AuNPs is enhanced and their aggregation and growth are suppressed. [DOI: 10.1380/ejssnt.2015.427]

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Silver nanoparticles were successfully synthesized by heating mixed solutions of silver nitrate, hexamethylenetetramine (HMTA), and polyvinylpyrrolidone (PVP) at 80°C for 7 min. The characterization of as-prepared silver nanoparticles were carried out by measuring ultraviolet-visible (UV-vis) and FTIR spectra, and images of transmission electron microscopy (TEM). The results of extinction spectra and TEM images indicated that the higher concentration of PVP and higher MW of PVP decrease the particle size of silver nanoparticles produced in the present systems. In addition, the interaction between silver atoms and oxygen atoms in the carbonyl group of PVP was also discussed by FTIR spectroscopy. It can be concluded that this heating method at 80°C is very useful for the preparation of stable and homogeneous silver nanoparticles in the present systems. [DOI: 10.1380/ejssnt.2015.431]

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Using non-equilibrium Green's function method, we have theoretically investigated electron transmission through [0001]-, [11-20]-, and [1-100]-oriented single-atom contacts (SACs) of Ti and found that all these SACs show transmission 2.3-2.4 at the Fermi level. The transmission sensitively varies with small perturbations of contact geometry but maintains its likeliest value at ∼ 2. Our results are compared with the experimental conductance histogram of Ti observed in our previous work (e-J. Surf. Sci. Nanotech. 12, 1 (2014)). [DOI: 10.1380/ejssnt.2015.435]

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We propose a new type of preparation method of silver nanoparticles (AgNps) by using a triazine benzenethiol derivative such as (4,6-dimethoxy-1,3,5-triazin-2-yl)-4-mercaptobenzoate (TBSH) as a reductant in the presence of a cationic surfactant such as cetyltrimethylammonium chloride (CTAC) or cetyltrimethylammonium bromide (CTAB). The formation amount and stability of AgNps in the presence of CTAC is compared with those in CTAB system; the addition of CTAC play important roles for the formation of AgNps. The optical properties of as prepared AgNps were characterized by using UV-vis, FTIR, and X-ray photoelectron (XPS). Transmission electron microscopy (TEM) images of as-prepared AgNps distinctly show the morphology of AgNps with average size of 30 nm. CTAC-concentration dependence of FTIR spectra indicates that the combination of rigid and compact network of TBSH and CTAC capped on AgNps significantly affects the size and shape of AgNps and also exhibit the presence of enhanced gauche conformers below the critical micellar concentration (cmc ∼ 0.6 mM) and trans conformers at cmc and above cmc of CTAC. Based on the present results, we propose a model of molecular structure and stability of AgNps. [DOI: 10.1380/ejssnt.2015.440]

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The two-dimensional concentration distribution of hydrogen peroxide (H₂O₂) generated by atmospheric-pressure argon (Ar) plasma jet irradiation was semiquantitatively determined using H₂O₂ test strips. An Ar plasma jet was generated with different applied voltages (5–10 kV) and Ar gas flow rates (3–10 L/min) and was irradiated onto the H₂O₂ test strips at different irradiation distances (2–40 mm) and irradiation times (5–30 s). The shape of the distribution of H₂O₂ concentration depended on the combination of the applied voltage, gas flow rate, and the irradiation distance and was classified into four types: circular, double-circular, ring-shaped, and double-ring-shaped. A circular distribution was observed for irradiation distances of ≥30 mm and a double-circular distribution was observed for irradiation distances of 10–20 mm. When the irradiation distance was ≤5 mm, a ring-shaped distribution was observed for applied voltages of ≤6 kV and a double-ring-shaped distribution was observed for applied voltages of ≥7 kV. [DOI: 10.1380/ejssnt.2015.474]

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A polyethylene terephthalate (PET)-based nanocomposite was prepared by using nanoclay-polyacrylic acid gel (nanoclay-PAA gel) as a reinforcing filler. For nanoclay-PAA gel, the cation-exchange method was used to prepare an organoclay from bentonite clay and hexadecyl trimethylammonium chloride. The organoclay was then dispersed in isopropanol, mixed with PAA gel (PAA powder swollen in water at room temperature to 1 wt%) under mechanical stirring, and neutralized with Triethanolamine (TEA). X-ray diffraction (XRD) showed an increasing of basal spacing and the intercalated structure of nanoclay gel was also found. The good distribution of organoclay in gel matrix were revealed with scanning electron microscope (SEM). PET/Clay nanocomposites with various inorganic clay contents (1, 2, 3, 4 and 5 wt%), were then prepared via melt mixing in a twin screw extruder. PET/Clay nanocomposites structure, phase morphology, thermal and mechanical properties of PET/Clay nanocomposites were investigated by XRD, SEM, differential scanning calorimetry (DSC), Thermo gravimetric analyzer (TGA) and universal testing machine, respectively. The results reveals the exfoliated and intercalated structures of nanoclay in PET/Clay nanocomposites, the improvement of thermal properties and the increasing of crystallinity, leading to the enhancement of mechanical properties. [DOI: 10.1380/ejssnt.2015.107]

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The career and my memories of Rohrer senseiI, together with a brief history of scanning tunneling microsocpy, are described for an introduction to presentations in the Dr. Rohrer Memorial Session. [DOI: 10.1380/ejssnt.2015.207]

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My memories about Dr. Heini Rohrer are described together with my researches inspired by the invention of STM. [DOI: 10.1380/ejssnt.2015.263]

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We studied the electronic, structural, and electrochemical modulation of electrostatic self-assembled thin films in which a nanoscale pair of single layer 1T-MoS₂ nanosheets and charge-compensating polymers as a counterpart in the self-assembly process stacked up on the substrate after heating. Heating the self-assembled monolayer and multilayers of the 1T-MoS₂ nanosheets at 300°C under vacuum triggered a yellow coloration and structural transformation, referred to as the 1T→2H transition, without a significant morphological change. In the topotactic conversion, an energy shift of the Mo 3d and S 2p core levels to a higher binding energy corresponds to the edge shift of the valence band, indicating the unique nature of this system as a MoS₂ molecule. The single layer state, which is often modulated by stacking the metallic-like 1T-MoS₂ nanosheets and the semiconductor 2H-MoS₂ nanosheets, was retained in the multilayers due to the robust interlayer galleries filled by the polymers. Cyclic voltammograms of a Li-ion battery using the 1T- or 2H-MoS₂ multilayer film electrodes provided useful information on the electrochemical reaction of the MoS₂ slabs, especially at the early stage of electrochemical Li insertion. These self-assembled ultra-thin films, offering well-defined MoS₂ nanosheet structures in terms of stacking order and crystal structure, will promote future applications of the single-layer 1T- and 2H-MoS₂ nanosheets. [DOI: 10.1380/ejssnt.2015.1]

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This paper proposes a method for fabricating gadolinium diethylenetriamine pentaacetic acid-immobilized silica particles (SiO₂/Gd-DTPA). Preparation of a colloid solution of spherical silica particles with an average size of 101.7±11.7 nm was performed by a sol-gel method at 35°C using 0.2 M tetraethylorthosilicate, 25 M H₂O and 0.01 M NaOH in ethanol. Amino groups were introduced on the silica particles with 6 × 10⁻³ M (3- aminopropyl)triethoxysilane (APES) at 35°C (SiO₂-NH₂), which resulted in their average particle of 80.5±9.7 nm. Gd-DTPA was immobilized on the SiO_2-NH₂ particle surface with 5 × 10⁻⁴ M Gd-DTPA in 50/50 (v/v) water/dimethylformamide solution at 35°C , which provided their average particle of 101.6±12.3 nm. The APES-introduction and the Gd-DTPA-immobilization did not change the spherical structure, and shifted an iso-electric point of particles to higher pH for the APES-introduction and then to lower pH for the Gd-DTPA-immobilization, which indicated that APES and Gd-DTPA were successfully attached on the particle surface with no chemical damage. A relaxivity value for T₁-weighted imaging of the SiO₂/Gd-DTPA particle colloid solution was 2.7 mM⁻¹ s⁻¹, that was 64% of that for Magnevist. [DOI: 10.1380/ejssnt.2015.42]

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Inorganic-organic composite materials are commercially utilized over a wide variety of industrial fields. The information on the distribution of inorganic and organic components on a nanometer scale is important for understanding the chemistry of the composite materials. In this study, the distribution of polycarbonate (PC) oligomer within a glass fiber reinforced PC was investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and principal component analysis (PCA). As a result, PCA indicated a component differentiating PC oligomer from PC polymer and revealed the homogeneous distribution of PC oligomer within the glass fiber reinforced PC. Therefore, a combination of ToF-SIMS and PCA is useful for identifying the detailed distribution of PC oligomer and evaluating the property of glass fiber reinforced PC. [DOI: 10.1380/ejssnt.2015.47]

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Electronic structures of donor-acceptor hetero-interfaces are crucial for performance of organic solar cell devices. In the present study, a well-defined organic molecular interface of pentacene single crystal and C₆₀ overlayer is elucidated by x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) and photoelectron yield spectroscopy (PYS). An energy level diagram at this hetero-molecular contact in the “head-on” orientation is derived, which reveals the vacuum level alignment and flat-band conditions. [DOI: 10.1380/ejssnt.2015.59]

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Three-dimensional microanalysis of the microstructure of organic materials is important in the development and progress of novel materials on the micro-to-nanometer scales. We have developed the three-dimensional microanalysis method using focused ion beams (FIBs) for section processing (shave-off scanning) and mapping for time-of-flight secondary ion mass spectrometry (ToF-SIMS). Shave-offscanning can effectively create an arbitrary section on a sample set against composite materials with a wide variety of shapes; three-dimensional sample images are then obtained by alternately operating two FIBs. From the simulation results, we could set the optimum condition of beam irradiation. In this study, we confirmed the enhancement of secondary ion intensity by Au deposition under ToF-SIMS mapping with the optimized condition, and examine the usefulness of the simulation. The enhanced maps of characteristic polystyrene (PS) fragment ions were obtained. In addition, we observed the distribution of Au deposition by mapping results. These maps showed same tendency. The intensity of PS fragment ions was enhanced according to existence of deposited Au particles. These results indicated that a precise analysis of 3D MetA-SIMS can be realized. [DOI: 10.1380/ejssnt.2015.65]

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A method of outer surface modification of glass nanopipette with chlorobenzene- terminated organopolysiloxane has been developed. Scanning electron microscope images and microscopic Raman spectra revealed the efficacy of the coating. Energy dispersive X-ray spectra showed not only the materials adsorbed on the nanopipette but also the change in stoichiometry of the bulk glass resulting from the fabrication process of the nanopipette with a laser puller. The coating method is easy to treat and can be used for various applications such as the prevention of carbon contamination from the materials during the injection to biomaterials such as living cells. [DOI: 10.1380/ejssnt.2015.79]

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Fe clusters grown on SrTiO₃ {001} surfaces were studied with UHV-TEM/STM combined system. Fe clusters have two types of epitaxial orientation relationships: one with a simple cube-on-cube with 45° orientation and the other with a higher index interface plane. The second one grows in twins. It was deduced that the clusters with the first orientation relationship have truncated pyramid shapes and stronger bonding energy and that the second one have near-roundish shapes with weaker bondings. The clusters influence each other so that their orientations deviate. [DOI: 10.1380/ejssnt.2015.85]

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The electronic structure of Ni₂P(0001) has been investigated by photoelectron spectroscopy (PES) utilizing synchrotron radiation. A Ni 3d–P 3p hybrid band was observed at 1-5 eV, and the band had peaks at 1.5 eV and 3.4 eV together with a shoulder around 2.4 eV. The resonant PES study showed that the Ni 3d component was included in the whole binding energy region of the band. The change in the surface electronic structure of Ni₂P(0001) induced by the segregation of P atoms was investigated by annealing temperature-dependent measurements of PES, and it was found that the change proceeded via following two steps: the segregation of P atoms proceeded at about 200°C, and the bonding between surface Ni atoms and segregated P atoms was facilitated at > 300°C. The bonding between Ni and P atoms induced substantial stabilization of Ni 3d levels, which is contrary to the case of Fe₂P(0001) where the segregation of P atoms induced little change in DOS of Fe 3d levels. [DOI: 10.1380/ejssnt.2015.93]

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Dynamic-mode atomic force microscopy (DFM) combined with Kelvin probe force microscopy (KFM) has been a powerful tool not only for imaging surface topography but also for investigating surface potential on a nanometer-scale resolution. We have developed DFM/KFM using a microfabricated cantilever with a lead zirconate titanate (PZT) piezoelectric thin film used as a deflection sensor. The observed sample can be in a completely dark environment because no optics are required for cantilever deflection sensing in our experimental setup, which is also equipped with a mechanism to irradiate ultraviolet (UV) light onto the sample. We prepared a platinum-on-silicon substrate and deposited fullerene-derivative (PCBM; [6,6]-Phenyl-C₆₁-Butyric Acid Methyl Ester) film patterns by vacuum evaporation with two shadow masks in crossed directions. The energy band diagram with band-bending, it was created by simultaneously obtaining topographic and surface potential images of the same area using the developed DFM/KFM. [DOI: 10.1380/ejssnt.2015.102]

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Platinum nano clusters, which are attractive material for highly activated catalysis, are usually evaluated by scanning tunneling microscopy (STM). Here we challenge to evaluate the structure of Pt nano clusters by reflection high-energy electron diffraction (RHEED) for the first time. The nano cluster models are made of n = 7 and n = 15 Pt atoms, which are deposited on TiO₂(110) substrate. The former has two dimensional (planer) and the latter three dimensional (two layer's) shapes. They are rotated around their [111] axes of Pt crystal, whose axes are also inclined from the substrate surface normal because of the atomically rough substrate surface. The RHEED patterns have been calculated by kinematic diffraction theory. From the calculated patterns for the two types of the clusters (n = 7 and 15), it is found that there is characteristic difference in the radial intensity distributions. The difference is attributed to existence or absence of the higher order reflections which arise from two layers of Pt(111). [DOI: 10.1380/ejssnt.2015.125]

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CO oxidation over a rutile TiO₂(110) surface supporting a tetrahedral Au₁₀ cluster has been examined by plane-wave DFT calculations. O₂ adsorbs sideon to the pentacoordinate Ti site of the oxide support with a large energy gain (∼ 2 eV), activated to a peroxide state. O₂ adsorption on the cluster is much weaker. The stability and activation state of sideon O₂ depends weakly on distance to the cluster. On a Ti site next to the cluster, a sideon O₂ reacts with CO adsorbed on the cluster to yield CO₂ with a very small energy barrier of 0.13 eV. On a more remote Ti site, a sideon O₂ reacts with a gaseous CO to yield CO₂ with a barrier of 0.55 eV. Thus, O₂ + CO reaction is much faster at the perimeter even for a small cluster such as Au₁₀. Similar results are obtained for a truncated pyramidal Au₉, except that a carbonate is formed at the perimeter. The carbonate formation is inhibited if H₂O is adsorbed next to O₂. [DOI: 10.1380/ejssnt.2015.129]

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We measured the frictional behavior acting on C₆₀ films at a small normal load as a function of oscillation amplitude using a MHz-range quartz crystal resonator and an optical AFM cantilever. The frictional behavior for C₆₀ films varies by the amplitude: For the amplitudes smaller than the C-C bond length of the C₆₀ molecule, the dynamic frictional force is directly proportional to the amplitude, while it becomes almost constant for larger amplitudes. Although the observation is in qualitatively the same manner as HOPG, the dynamic frictional force for small amplitudes is significantly larger than that of HOPG. This difference suggests that C₆₀ molecules easily tilt and/or rotate when the tip slides in C₆₀ films, and the dynamic friction arises from the tilting and/or rotating motion. [DOI: 10.1380/ejssnt.2015.135]

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Electric field-induced change of magnetic properties in ferromagnetic Fe thin film grown on a ferroelectric BaTiO₃ (BTO) substrate is studied by means of x-ray absorption spectroscopy. We find that a few nm Fe oxide layer exists at the Fe/BTO interface when the Fe thickness is 8 nm, in which the film shows in-plane magnetization. The x-ray magnetic circular dichroism analysis reveals that the coercive field, H_c, of Fe shows a hysteresis behavior as a function of the electric field, and larger H_c is observed at ∼ ±3 kV/cm. On the other hand, it is found from the extended x-ray absorption fine structure analysis that the Fe-O bond distance shows a similar electric field dependence to that of H_c, and shorter distance is observed at ∼ ±3 kV/cm. Therefore, it is assumed that the H_c strongly depends on the ferroelectric domain structure of BTO, and larger H_c is observed for the multi-domain structure. We suppose that shrinking of the Fe–O distance caused by the domain formation leads to an enhancement of H_c due to the island-like localization of the interface Fe oxide. [DOI: 10.1380/ejssnt.2015.139]

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TiO₂ photocatalysts can remove harmful substances such as volatile organic compounds (VOCs) under light irradiation. However, they are only activated by ultraviolet light at wavelengths shorter than about 380 nm, so they cannot be used under visible light irradiation. Thus, visible-light-responsive photocatalysts have been studied extensively to enable their indoor use. TiO₂ powder supported with Cu(II) ions (Cu(II)/TiO₂) has recently been reported to possess visible-light photocatalytic activity. In the present study, we used cupric acetate as a Cu(II) source. We prepared various Cu(II)/TiO₂ photocatalysts by changing the amount of cupric acetate and assessed their photocatalytic performance. The performance of Cu(II)/TiO₂ photocatalysts was estimated from the rate of decrease in the formaldehyde (HCHO) concentration in the flowing stimulant air under irradiation by a fluorescent lamp or a white LED. The surface properties of Cu(II)/TiO₂ photocatalysts were analyzed by X-ray photoelectron spectroscopy (XPS) measurements. The optical reflectance of Cu(II)/TiO₂ photocatalysts was measured by using a UV-Vis spectrophotometer. The maximum visible-light photocatalytic activity was observed at a Cu/TiO₂ weight ratio of 5.69 [wt%]. The maximum rate of decrease in the HCHO concentration of the Cu(II)/TiO₂ photocatalyst was higher than twice that of a typical commercial TiO₂-based visible-light-responsive photocatalyst (Ishihara-Sangyo MPT-623) under the same test conditions. [DOI: 10.1380/ejssnt.2015.143]

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The effects of Zn atoms as a dopant on the surface structure and initial growth processes on InP(111)B substrate are theoretically investigated on the basis of surface phase diagrams which are obtained by comparing the adsorption energy given by ab initio calculations with the gas-phase chemical potentials. The calculated surface phase diagrams demonstrate that the Zn-incorporated surface is stabilized under the growth conditions with high Zn supply ratio. Furthermore, In atoms tend to easily adsorb on the Zn-incorporated surface as an In–P dimer due to the formation of Zn–P and P–P bonds, implying that the adsorption of In atoms and resultant growth processes are promoted on the Zn-incorporated InP(111)B surface which is stabilized under Zn-rich conditions. These results suggest that effects of Zn doping on the surface structure and initial growth processes are crucial for understanding the bidirectional growth mechanisms of InP nanowires on InP(111)B substrate. [DOI: 10.1380/ejssnt.2015.147]

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We performed low-temperature scanning tunneling microscopy and spectroscopy on Si(111)-(√7 × √3)-In in magnetic fields. Superconducting vortices were observed by mapping zero-bias conductance in an area consisting of flat terraces separated by atomic steps. While vortices in the terrace regions have an isotropic shape with a normal-state core, those at the atomic steps have anisotropic shapes and the superconductivity is only weakly suppressed in the cores. These properties are understood as a crossover from a normal vortex to a Josephson vortex. We conclude that the atomic steps work as Josephson junctions limiting the density of supercurrents. [DOI: 10.1380/ejssnt.2015.151]

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Langmuir-Blodgett (LB) monolayers of octaoctyloxy metallophthalocyanines (MOOPc, M = Cu, Zn) and copper tetra(tert-butyl) phthalocyanine were deposited on glass substrates. MOOPcs showed gradual increase in their surface pressure-area isotherms reflecting their flexible substituents. In spite of the similar molecular structure, Cu and ZnOOPc indicated different isotherms at lower pressure, manifested by the surface morphology. At high surface pressure, ZnOOPc monolayer became denser than CuOOPc monolayer, as was estimated by the optical absorption. These results represents that the central metals have a crucial effect on structures of LB monolayers. [DOI: 10.1380/ejssnt.2015.155]

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Mechanisms of triboluminescence of silica glass are discussed from a theoretical viewpoint on the basis of several experimental reports on triboluminescent spectra of a variety of silica glasses. Until now, two different mechanisms have been proposed for triboluminescence of silica glass. Triboluminescent spectra with a single peak were regarded as the emission from a black-body radiator, but spectra with two peaks were interpreted as the emission from defect centers. We here propose a model for explaining the two types of triboluminescent spectra reported in silica glass. In our model, triboluminescence of silica glass is due to the emission from defect centers near fracture surfaces. Radiative relaxation of electronic states on these defects would explain the two types of triboluminescent spectra reported in silica glass. Triboluminescent spectra of silica glass depend on fracture methods which influence disorder in atomic configuration near fracture surfaces. [DOI: 10.1380/ejssnt.2015.159]

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We carried out the surface mapping of the dynamic friction and the effective elastic stiffness of contact by using a quartz crystal resonator and an AFM cantilever, associated with the topographic image. The tip was scanned across the Au substrate on the resonator in the constant-height mode. A typical grain structure of the Au substrate in the dynamic friction and the effective stiffness images was observed, simultaneously with the topographical image. This technique enables us to observe the surface properties related to contact in the nanometer scale. [DOI: 10.1380/ejssnt.2015.164]

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We propose an experimental methodology for producing silicon carbide (SiC) films on Si substrates using an ion beam induced chemical vapor deposition (IBICVD) technique with methylsilane (SiH₃CH₃) as a gas source. Both methylsilane gas (1.2 sccm) and Ar ion beam (100 eV, 5μA) were simultaneously introduced onto Si(100) substrates. Temperatures of Si substrates were set at 600, 700, or 800°C. A SiC thin film was formed by the simultaneous introduction of methylsilane and Ar ions onto the Si substrate when the substrate temperature was 600°C. On the other hand, in the cases of 700 and 800°C, SiC films were formed by methylsilane gas alone and SiC film deposition rates by methylsilane gas with the Ar ion beam were approximately identical with those obtained without the Ar ion beam. We therefore conclude that the IBICVD technique with methylsilane is useful for SiC film formation on Si at relatively low substrate temperatures. [DOI: 10.1380/ejssnt.2015.174]

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The influence of ZnO-MgO mixed metal-organic decomposition (MOD) coating materials have been investigated based on crystal growth and film properties of ZnO-MgO mixed thin films. These mixed thin films were grown on quartz substrates by dip coating and then sintered at 550°C. The film properties were evaluated using an atomic force microscope and a UV-VIS-NIR spectrophotometer, and by performing X-ray diffraction measurements. The growth mechanism is changed by MgO in ZnO-MgO mixed MOD coating materials. Mg segregated to the surface side in the ZnO-MgO mixed thin film, and some of the segregated Mg formed ZnMgO. In addition, the grain size of ZnO-MgO mixed thin films increased with an increase in the amount of MgO additive. Therefore, it can be concluded that grain boundary segregation of Mg enhances crystal growth. This enhancement of crystal growth by the intentional addition of an impurity can be applied to improving the characteristics of other semiconductor materials. [DOI: 10.1380/ejssnt.2015.185]

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The structural change in InAs(001)-(2×3) wetting layer surfaces grown on GaAs is investigated using ab initio-based approach incorporating temperature T and beam equivalent pressure p. Our calculated results reveal that the (2×3) surface fully covered by As dimers is unstable while the (n×3) surfaces (n =4, 6, and 8) with (n −1) dimers including In-As and one missing dimer is more stable at the conventional molecular beam epitaxial (MBE) growth conditions such as T = 703 K under p_In = 1:0×10^-7 Torr and p_As4 = 7:5×10^-7 Torr. On the (n×3) surfaces, In atoms are incorporated through In-As dimer formation with As desorption. The resultant (4×3) surface consists of three In-As dimers and one missing dimer. The (6×3) surface has three In-As dimers, two As dimers, and one missing dimer. Only one In-As dimer emerges with six As dimers and one missing dimer on the (8×3) surface. The missing dimer region becomes favorable site for further In adsorption. Moreover, the (8×3) can easily change to the (4×3) with In adsorption and subsequent As dimer desorption on the initial (8×3). The existence ratio R for the (4×3) and (6×3) units is respectively estimated to be R = 0:70 and 0.30 satisfying 0.375 ML desorption of As on the (2×3) to form the (2×4)α2. This is consistent with experimental results. Consequently, the (n×3) surfaces including In-As dimers appear during MBE growth instead of the (2×3) surface with As-dimers. [DOI: 10.1380/ejssnt.2015.190]

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Adsorption interactions between adsorbate of volatile organic compound (VOC) and adsorbent film were investigated using Kelvin probe force microscopy and differential force microscopy. An adsorbent film with carbonaceous columnar structures was prepared using radio-frequency sputtering of pectin. The VOCs were identified by their dielectric constants, polarizabilities, and refractive indices. Polar VOCs enhanced the interaction forces and negative surface potentials of the adsorbent films. The negatively charged potential showed thermal drift, which is stronger for polar VOCs. Thermal release of electrons trapped in the surface states by band bending was enhanced by the adsorption of polar species. Activation energy is closely correlated with the negative shift of the surface potential. Quantitative structure property relationship analyses suggest that the local charges of adsorbate VOCs are crucial for these surface properties: surface potential, surface interaction force, and adsorption amount. [DOI: 10.1380/ejssnt.2015.195]

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The growth of gold on top of a n-alkane monolayer, which consists of lamellar assemblies with close-packed flat-lying chains, is observed by using scanning tunneling microscopy. The n-alkane monolayer sustains gold atoms,and penetration of the atoms into the monolayer is inhibited. The molecular conformation is unaffected and the arrangement is only slightly changed upon deposition of the gold atoms. Two-dimensional clusters are grown and a smooth monolayer is finally obtained. [DOI: 10.1380/ejssnt.2015.209]

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Titanium dioxide (TiO₂) photocatalysis can be applied to pattern proteins and cells under aqueous solution. In this work, we extended the application of this technique to patterning primary neurons, a type of cell with relatively weak adhesibility. For this purpose, we employed ribosomal protein L2 (RPL2) that has high affinity toward silica and metal oxides, including TiO₂, to stably bind a neuronal adhesion protein laminin to the TiO₂ surface. We utilized two types of molecular recognition to achieve this—binding of anti-laminin antibody to its antigen (laminin) and binding of protein A to the antibody. We show that a protein complex consisting of laminin/anti-laminin antibody/protein A-RPL2 is spontaneously formed by simply mixing the precursor proteins in solution phase. We then show that the surface coated with the protein complex supports stable growth of rat hippocampal neurons. Finally, we show that the cells can be selectively grown on the protein complex patterned with the TiO₂-assisted method. The protocol established in this work is a unique combination of a top-down micropatterning of the surface using TiO₂ photocatalysis and a bottom-up self-assembly of biomolecules, which can be further applied to pattern a wide range of proteins and cells. [DOI: 10.1380/ejssnt.2015.213]

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We have succeeded in forming flocculates of gold nanoparticles (AuNPs) using DNA and RNA bases to obtain their surface enhanced Raman spectra. Adenine, guanine and cytosine molecules which possess a primary amino group (-NH₂) formed flocculates at much lower concentration than uracil and thymine without an -NH₂ group, suggesting a crucial role of an -NH₂ group for adsorption of these base molecules on neighboring AuNPs. Detailed adsorption structure of base molecules was investigated using their SERS spectra at various pH in solutions and those for deuterated bases, comparing with those for bulk state and also by DFT calculations. [DOI: 10.1380/ejssnt.2015.223]

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We investigate the origin of repulsive interactions between atomic steps on vicinal solid surfaces using a first principles approach. Peculiar electronic states localized near step edges are found in (11-2n) nanofacets formed on the 4H-SiC(0001) vicinal surface. The localized states are gradually overlapped between the steps with shrinking the distance between atomic steps. From a viewpoint of energetics for (11-2n) nanofacets, the presence of the repulsive interaction between atomic steps is expected. We then suggest that the overlap between electrons distributed around step edges is a possible origin of the step-step repulsive interaction. [DOI: 10.1380/ejssnt.2015.231]

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