Ultrathin films of Bi₂Se₃ grown on Si(111) substrate were etched into submicron-width wires by using a focused ion beam (FIB), and their electrical resistance was measured using the four-probe method with a four-tip scanning tunneling microscope. All of the procedures were performed in situ in ultrahigh vacuum without exposing the sample to air. One-dimensional conduction of the films was confirmed from the dependence of the resistance on the length of wire under measurement, meaning that successful lossless current path control laterally as well as vertically can be obtained with FIB etching. Protecting the sample surface from unintentional gallium ion beam irradiation in the FIB process was also found to be important for maintaining the intrinsic electrical properties of the Bi₂Se₃ films. [DOI: 10.1380/ejssnt.2014.423]

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This review describes how the manipulation of single molecules on solid state surface is available in air or at the liquid/solid interface, observed with scanning tunneling microscope (STM). First, the influences of the STM tip on the observation and manipulation of molecules are discussed. Then how the STM tip induced the ordering and how the molecular structures on the surface can be manipulated are shown. Second, the manipulation of single molecules with STM tip is demonstrated. Last, the STM observations of the manipulation of molecules by changing the ambient conditions such as solvent, photon irradiation, and electrochemical potential, are shown. [DOI: 10.1380/ejssnt.2014.157]

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The surface alloying is the important topics in Ni₂P study which is expected for next generation hydrodesulfurization and hydrodenitrogenation catalyst. The atomic structure and catalytic properties of a single crystalline Ni₂P surface modified with W (W-Ni₂P) was investigated by photoelectron diffraction (PED) and spectroscopy. PED is an element and site selective surface structure analysis method that enables observation of three-dimensional atomic configurations of the surface local structure. The selective replacement of W to the Ni site in the Ni₂P crystal was clarified by PED. Chemical reactivities for NO molecules of the W-Ni₂P and the clean Ni₂P surfaces were compared. On the clean Ni₂P surface, the NO adsorption did not occur, whereas W-Ni₂P surface showed remarkable activity for NO adsorption. [DOI: 10.1380/ejssnt.2014.53]

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We demonstrate one-step deposition of submicrometer-sized particles suspended in the gas-phase onto a plate type substrate using an electrostatic-assisted spray system. The spray nozzle was set perpendicularly to the substrates (facing the front surface). The particles were deposited on plate-type metallic surfaces, on both front and rear sides of the substrate. This “both-side” deposition can be ascribed to deflection of charged particles in the front side, and then drifting of the particles around the rear side. A numerical simulation also showed that the deposition mechanism was found to be dependent on the center and the edge of the substrate. The electrostatic effect is more effective on both the center and the edge than the diffusion effect. [DOI: 10.1380/ejssnt.2014.238]

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Fly ash (FA) was hydrothermally treated in an alkaline solution to produce zeolite X (Z-FA). The properties of the FA and Z-FA were then investigated. The FA consisted of spherical particles of various diameters. The X-ray diffraction patterns of FA and Z-FA showed that the FA mainly consisted of mullite crystals (3Al₂O₃·2SiO₂), while the Z-FA consisted of zeolite crystals. The specific surface area (23.3 m²/g) and pore volume (57.6 μL/g) of the Z-FA were greater than those of the FA (2.7 m²/g and 12.7 μL/g, respectively). The pH_pzc of the FA and Z-FA were 7.94 and 9.81, respectively. [DOI: 10.1380/ejssnt.2014.23]

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In this study, first principles calculations based on density functional formalism were used to evaluate optimized structures, spontaneous polarizations, and effective charges for Sn(Zr_0.5,Ti_0.5)O₃ (SZT), Ge(Zr_0.5,Ti_0.5)O₃ (GZT), (Pb_0.875,Sn_0.125)(Zr_0.5,Ti_0.5)O₃ (PSZT), and (Pb_0.875,Ge_0.125)(Zr_0.5,Ti_0.5)O₃ (PGZT); the results were compared with corresponding values calculated for Pb(Zr,Ti)O₃ (PZT). The stability of the calculated crystal structures differed depending on whether all Pb atoms were replaced (100% substituted materials, SZT and GZT) or whether only 12.5% of Pb atoms were replaced (12.5% substituted materials, PSZT and PGZT): the structures of 100% substituted materials were compressed and unstable, while the 12.5% substituted materials maintained stable structures. Both the 100% and 12.5% substituted materials had values of spontaneous polarization nearly as large as that for PZT. For 100% substitutions, atomic displacements increased and effective charges decreased relative to values for PZT. For 12.5% substitutions, atomic displacements also increased, and the effective charge along the macroscopic polarization axis decreased due to changes in covalent bonding. We evaluated the piezoelectricity of the materials by calculating the barriers to change in polarization axes. For 100% substituted materials, the barriers were larger than that for PZT, while for 12.5% substituted materials, the barriers were smaller. Therefore, 100% substituted materials have weaker piezoelectric properties than PZT, but 12.5% substituted materials have stronger piezoelectric properties. We conclude that 12.5% substituted materials maintain the crystal structure of PZT and probably have better piezoelectric behavior than PZT. [DOI: 10.1380/ejssnt.2014.40]

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To determine how the three-dimensional (3D) shapes of scaffolds influence cell migration, 3D micro-patterned scaffolds with various shapes were fabricated on a silicon substrate (725 μm thick, 10 mm×10 mm quadrate) by using photolithography. We imaged living cells on a silicon substrate over 72 h using a novel simple method. NIH-3T3 cells were adhered to the silicon substrate, which was then placed face-down or face-up into culture medium in a 35 mm (12φ) glass-bottomed dish. In this method, there is a sufficient gap (1.3 mm) between the downward-facing cells and the bottom of the plate for the culture medium to diffuse over the cells. Cell growth over 72 h was similar in both conditions. NIH-3T3 cells were adhered to three kinds of 3D micro-patterned scaffolds, placed face-down into culture medium in glass-bottomed dishes, and cell migration and the scaffolds were observed over 72 h. The three scaffolds differed only in terms of the unit shape of the repetitive pattern, namely a scale structure with equilateral triangular pores, a check structure with regular tetragonal pores, or a stripe structure with rectangular grooves. These scaffolds had a constant pore ratio (50%), pore depth (22 μm), and subcellular pattern size. The angle at which cells turned correlated with the unit shape of the scaffold: the interior turning angles were multiples of 60° on a scale structure with equilateral triangular pores, multiples of 45° on a check structure with regular tetragonal pores, and close to 0° or 180° on a stripe structure with rectangular grooves. Therefore, the angle that cells turn is influenced by the unit shape of the 3D patterned scaffold on which they are cultured. Furthermore, when the angles at which the migrating cells turned were investigated in detail, it was found that a cell turns in one of two directions that correlate with the unit shape of the scaffold; one corresponding to the edge of the pattern, and the other corresponding to the upper surface of the pattern. These differences in the angles that migrating cells turned correlated with differences in the angles they extended protrusions. The angles of cell protrusions markedly differed between the three different scaffolds, which partly underlies why migrating cells turned at different angles. In summary, the unit shape of the micro-patterned scaffold affects the angle at which cells extend, which in turn affects the angle at which migrating cells turn. [DOI: 10.1380/ejssnt.2014.289]

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We study the surface-roughness dependence of the Casimir force between fractal surfaces, which is represented by the Weierstrass-Mandelbrot function. When compared the Casimir force in the case of smooth surfaces, the Casimir force between fractal surfaces rapidly increases as the separation distance decreases. We express this deviation as a simple analytical function that is composed of three parameters including fractal dimension, and compare it with the deviation obtained from Monte Carlo simulations. [DOI: 10.1380/ejssnt.2014.313]

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We have developed a new Reverse Monte Carlo code, called the micro Reverse Monte Carlo (m-RMC), which is applicable to structure analysis of nanomaterials and surface species. In the m-RMC, Reverse Monte Carlo is applied to an ensemble of replica files, each of which contains one molecule or one small cluster, because the Extended X-ray Absorption Fine Structure (EXAFS) is sensitive to short-range structures and has negligible interaction between molecules or clusters. We apply the m-RMC to face-centered cubic metals (Cu, Pd, and Pt) and discuss the advantages, validation, and problems of the m-RMC. The bond distance and some cumulant coefficients can be determined from the EXAFS using m-RMC. Some 50-100 replica files are sufficient to reproduce the EXAFS oscillations and radial distributions. The bond distance can be determined, including the asymmetric distributions,by m-RMC. We also apply m-RMC to α-MoO₃ and Au clusters. The m-RMC analysis of MoO₃ shows that three radial distribution peaks appear corresponding to three types of Mo–O bonds. The m-RMC analysis of Au cluster indicates the presence of Au₅₅ cuboctahedral structure with Au-Au distance at 0.288 nm. We obtain a 3 D image of Au₅₅ nanocluster from the unified file. The m-RMC method can be applied to the analysis of the EXAFS for chemical systems with appropriate care. [DOI: 10.1380/ejssnt.2014.322]

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A silicon nanowire-based immunosensor has been developed to determine the presence of 8-hydroxy-2'-deoxyguanosine (8-OHdG). This research demonstrates a process for the detection of 8-OHdG, which is an oxidative stress biomarker, in which elevated concentrations in urine and saliva can act as an indicator of the presence of acute leukaemia, colorectal, breast, lung and prostate cancers. The detection of elevated levels of this biomarker is critical in determining the presence of various mutagenesis and can be used to diagnose early stage cancer before initial symptoms appear. The surface functionalization process has involved the attachment of diazonium salt to the silicon nanowire surface with further stage which involves the reduction of PhNO₂ to PhNH₂. The antibody targeted against 8-OHdG was subsequently bound to the amine NH₂ modified grafted layer of a 370 nm width nanowire. The immunosensor was evaluated through the use of current/voltage electrical probe monitoring in which a 2 μg/ml concentration of 8-OHdG was detected. A further comparison with phosphate buffered saline solution added to the sensor was observed to be negligible. The antibody-functionalised SiNW sensor has been used to detect binding of the 8-OHdG biomarker to the SiNW surface within sixty-seconds of exposure, making this a rapid cancer biomarker test. [DOI: 10.1380/ejssnt.2014.349]

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The binding energies of the heavy-hole and light-hole exciton in a GaAs spherical quantum dot have been calculated using variational technique within effective mass approximation. The effect of pressure and temperature are also analyzed. Our result shows that exciton binding energy (i) decreases as the dot radius increases, (ii) further increases with increase in pressure and decreases with increase in temperature, and (iii) approaches zero as dot size approaches infinity. All the calculations have been carried out with finite models and results are compared with exciting literatures. [DOI: 10.1380/ejssnt.2014.358]

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Field emission microscopy is commonly used to observe patterns and intensities of electron emissions and to estimate the average work function from the emission current with respect to the applied voltage (F-N plots). However, it is difficult to observe the nanostructure at the apex of the tip using only field emission microscopy. In this research, we investigated the possibility of characterizing the surface of an electron emitter using scanning probe microscopy (SPM). Adding an optical microscope and a light source to the front side of the SPM system, we succeeded in precisely confirming the relative positions of an SPM cantilever and an electron emitter and in observing the surface structure at the top of an electron emitter in a 5 × 5 μm² region. SPM and scanning electron microscopy images were compared, and both showed grains and their boundaries. Higher magnification SPM images showed flat and concentric circular ring-shaped planes. [DOI: 10.1380/ejssnt.2014.377]

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To clarify the mechanism underlying the inactivation of Escherichia coli (E. coli) cells subjected to atmosphericpressure argon (Ar) plasma jet irradiation, we focused on phospholipids, the main components of the cell wall and membrane of E. coli. Commercially available standard samples of phospholipids, phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were irradiated with an atmospheric-pressure Ar plasma jet in air for 5 s. The phospholipids irradiated with the plasma jet were separated by thin-layer chromatography (TLC), and the results showed that PE was unchanged even after plasma jet irradiation, whereas PG was degraded into several substances. One of them was identified as lysophosphatidylglycerol (LPG), a lysophospholipid of PG, by liquid chromatography-mass spectrometry (LC-MS). From these results, we inferred that PG in the cell wall and membrane was degraded into LPG and a fatty acid by plasma jet irradiation, and that the cell wall and membrane were disrupted, inactivating E. coli. [DOI: 10.1380/ejssnt.2014.400]

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Nickel hydroxide (Ni100) and nickel hydroxide, including cobalt (NiCo91), were calcined at different temperatures. These materials were investigated by analyzing data obtained from X-ray diffraction (XRD), scanning electron microscopy, specific surface area, thermogravimetric-differential thermal (TG-DTA) technique, and electron-probe microanalysis. The XRD and TG-DTA data obtained indicated that calcination at 250–270°C can promote the conversion of Ni(OH)₂ into NiO, and that cobalt hardly affected the structural changes of nickel hydroxide. The specific surface areas of Ni100 and NiCo91 were determined to be in the range 17.9–148.3 and 21.0–145.1 m²/g, respectively. The specific surface area increased suddenly at 260°C. The amount of phosphate adsorbed onto Ni100 and NiCo91 was measured to be in the range 29.2–44.7 and 29.7–54.0 mg/g, respectively. The amount adsorbed onto Ni100 or NiCo91 was greater than that onto another adsorbent previously reported. The correlation coefficient relationships between the specific surface areas of Ni100 and NiCo91 and the saturated amount of the adsorbed phosphate ions were found to be 0.935 and 0.960, respectively. These results suggested that adsorption of phosphate ions with Ni100 or NiCo91 is related to the specific surface area. Our study demonstrated that Ni100 and NiCo91 can be considered as promising materials for the adsorption of phosphate ions from aqueous solutions.[DOI: 10.1380/ejssnt.2014.404]

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An atmospheric-pressure argon (Ar) plasma jet was directly irradiated onto distilled water. Semiquantitative determination using test strips and flow injection analysis (FIA) revealed that nitric acid (HNO₃) and nitrous acid (HNO₂) were generated in distilled water by plasma jet irradiation for 1 min. The nitrate ion (NO₃^- ) and nitrite ion (NO₂^- ) concentrations in distilled water irradiated with a plasma jet, determined from the test strips,were in good agreement with those determined by FIA. The NO₃^- concentration in distilled water proportionally increased with the plasma irradiation time, whereas the NO₂^- concentration was almost unchanged. It is considered that high-energy electrons in the plasma jet collided with nitrogen molecules (N₂) and oxygen molecules (O₂) to generate nitrogen (N) and oxygen (O) radicals. Nitrogen oxide (N_xO_y) generated upon the reaction of the radicals is considered to react with water molecules (H₂O) in air and at the surface of distilled water to generate HNO₃ and HNO₂. [DOI: 10.1380/ejssnt.2014.410]

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We have performed sum frequency generation (SFG) spectroscopy of water molecules on a polycarbonate (PC) film with and without 1 minute O₂ plasma exposure. The intensity of SFG signal corresponding to the O-H stretch vibrations of water at a water/PC film interface was ∼1000 times as low as that of signal from a water/quartz interface. In the SFG spectrum of water facing a pristine PC film, peaks at 3270 and 3440 cm^-1, and a shoulder at 3620 cm^-1 were observed. In the SFG spectrum of water on the film exposed to O₂ plasma, peaks were observed at 3200 and 3450 cm^-1. The peak at 3270 cm^-1 red-shifted to 3200 cm^-1 by the O₂ plasma exposure. The intensity of the peak at 3200 cm^-1 was higher than that at 3450 cm^-1. The shoulder at 3620 cm^-1 disappeared after the O₂ plasma exposure. The modulations of these peaks represent that the packing structure of water molecules was more ordered on the film after the O₂ plasma exposure. [DOI: 10.1380/ejssnt.2014.414]

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The twin structure of monoclinic ZrO₂ nanofiber was characterized using transmission electron microscopy. The m-ZrO₂ nanofiber with diameter ∼300 nm was grown by the thermal oxidation of ZrSi₂ with gallium. The (011) twinning was observed periodically along the growth direction of m-ZrO₂ nanofiber. [DOI: 10.1380/ejssnt.2014.418]

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PS/CdS, PVC/CdS & PMMA/CdS polymeric nanocomposite samples were prepared through dispersion solution casting technique. The CdS nanoparticles were prepared by simple chemical method using CdCl₂ and H₂S gas produced from thiourea. The nanoscale morphology of the polymer nanocomposite samples was characterized using small angle x ray scattering (SAXS). SAXS reveals that CdS interact well with the polymer matrix and exhibit their nano nature. [DOI: 10.1380/ejssnt.2014.420]

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A theory is derived for light emission by localized plasmon excitation by developing our existing theory of localized bulk and surface plasmons for metal nanostructures to consider the retardation of the scalar potentials. Using the retarded scalar and vector potentials, the electromagnetic fields that are emitted by the electric dipole moments induced by localized plasmons are derived, which in turn give the frequency and angular dependences of the intensity of the light that is emitted from the metal nanostructures. The emitted light intensities are analytically calculated for metal nanospheres with step function-like electron densities at their surfaces when electric fields and electrons are incident on those surfaces. The model calculations show that localized surface plasmon excitation only contributes to the light emission because of the coupling between localized bulk and surface plasmons. [DOI: 10.1380/ejssnt.2014.431]

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Break junctions of some HCP metals are known to yield single-atom contacts (SACs) frequently at 4 K but rarely at room temperature (RT). In this work, we show that SACs of Cd and Ti can be produced at RT not by opening their junctions but by closing them. For both Cd and Ti, the conductance histogram measured at junction closing reveals a clear SAC peak whereas the SAC peak appears marginal in the histogram obtained at junction opening. Because SACs are formed through necking deformations in the junction opening, while not in the junction closing, our observations suggest that the rare SAC formation reported for some HCP break junctions at RT would be due to necking deformations. The observed histograms also determine the hitherto unknown SAC conductance of Cd and Ti as 0.7G₀ and 0.8G₀, respectively. [DOI: 10.1380/ejssnt.2014.1]

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Nitrogen-pair formation processes on the GaAs(001)-(2×4) surfaces found experimentally are systematically investigated using ab initio-based approach incorporating beam equivalent pressure p (p_As = 3.0 × 10^-6 Torr, p_N = 7.0 × 10^-6 Torr) and temperature T = 830 K. The calculated surface phase diagrams elucidates that the (2×4)α1 and (2×4)α2 surfaces are stable at the growth conditions under As₂ and As₄, respectively. The Monte Carlo simulations reveal that the N incorporation on the (2×4)α1 and (2×4)α2 surfaces proceeds with increase of energetically favorable Ga-N bonds in the third layer via series of events such as adsorption of N-As dimer, substitution of N for As located in the third layer, and As dimer desorption to form the N-pair in the third layer. It is also found that the probability of the N-pair formation on the (2×4)α1 surface is much larger than that on the (2×4)α2 surface. This is because the strain around the N-pair on the (2×4)α1 surface is smaller than that on the (2×4)α2 surface where N-As surface dimer is formed to relax the larger strain. Furthermore, the N-pair formation probabilities P under As₂ and As₄ are estimated as a function of temperature including (2×4)β1. N atoms incorporated on the GaAs(001) surface can form N-pair along [110] with P ∼ 0.8 on the surface with two phase mixture of (2×4)α1 and (2×4)α2 at T = 830 K under As₂ and As₄. [DOI: 10.1380/ejssnt.2014.6]

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Electronic excitation energy transfer is studied theoretically within a prototype system of quantum dots using the excitonic representation of the electronic states of two quasi-zero dimensional subsystems, between which the excitation energy is transferred in a process treated as an irreversible kinetic phenomenon. The electron-phonon interaction, included in an approximation going beyond the limits of finite order perturbation calculation, is used when considering the so called uphill and downhill excitation transfer processes. The theory is deveped upon utilizing a simplified model of two interacting quantum dots, both coupled to their environment. The theoretical approach is documented by numerical calculations. The results should be relevant to various cases of the electronic excitation energy transfer between quasi-zero-dimensional nanostructures. [DOI: 10.1380/ejssnt.2014.11]

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The effects of dopants on the crystal structure of InP and GaAs NWs are theoretically investigated by means of density functional calculations. The calculated energy differences among various crystal structures with substitutional Zn (C) atoms in InP (GaAs) are found to be similar to those of bulk phase. This indicates that the contribution of dopants to the energy difference among different crystal structures in NWs is negligible. Furthermore, we reveal that the difference in the step-edge formation energy between zinc blende and wurtzite structures with dopants is similar to that without dopant within 0.01 eV/Å. These results thus imply that the role of dopants for the supersaturaion of nanowire formation is crucial to determine the crystal structure of NWs. [DOI: 10.1380/ejssnt.2014.18]

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We report on changes of surface structures induced by hydrogen adsorption on a Jahn-Teller distorted magnetite (Fe₃O₄)(001) surface and priorities of hydrogen-adsorbed sites by means of in-situ scanning tunneling microscopy. The experiments have revealed that surface Fe cations relax toward the bulk-terminated positions by OH species formed between adsorbed-hydrogen and surface O_N anion (The labeled “N”in O_N denotes that the O-O distance in the surface is compressed compared with bulk). Moreover, two types of surface O_N sites were found to be almost equivalent for hydrogen adsorption. [DOI: 10.1380/ejssnt.2014.26]

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In order to exploit graphene (Gr) as a transparent electrode in organic optoelectronics, a profound understanding of molecular wetting and diffusion processes on this material is essential. Properties of Gr like band structure, work function, or elasticity depend significantly on the layer number. Here, we report on Gr layer dependent differences in the growth morphologies of hot wall epitaxy deposited sub-monolayer thin films of the one-dimensional conjugated parahexaphenyl (6P) molecule on exfoliated Gr/SiO₂. At deposition temperatures around 363 K, 6P forms straight needles arranged in regular networks on single layer graphene. Within the first four Gr layers, the average needle height increases and the average needle length decreases thereby reducing the specific 6P-Gr interface area. The variations in morphology and wetting behavior with the Gr layer number arise from changes in the growth kinetics induced by differences in adhesion and diffusion properties with Gr thickness. [DOI: 10.1380/ejssnt.2014.31]

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The atomic arrangements of zinc blende structured GaN_xAs_1-x nanowires (NWs) surrounded by semiconductor templates are theoretically investigated using empirical interatomic potentials and Monte Carlo simulations. Our calculations demonstrate that the atomic arrangements of GaN_xAs_1-x NWs strongly depend on nitrogen composition x and substrate lattice constant a_sub. For a certain nitrogen composition and substrate lattice constant, layered segregation is found in GaN_xAs_1-x NWs surrounded by templates. On the other hand, surface segregation appears on the side facets of freestanding NWs over the wide range of x and a_sub. The surface segregation in freestanding NWs originates from the energy difference between Ga-N and Ga-As bonds, which leads to the preference of As atoms at the topmost layer of side facets. These calculated results thus suggest that various novel atomic arrangements in GaN_xAs_1-x NWs can be realized depending on x and a_sub which control degree of lattice constraint. [DOI: 10.1380/ejssnt.2014.45]

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Ordered chromium islands of nanometer sizes formed by sub-monolayer Cr deposition on Au(111) have been studied in this work by scanning tunneling microscopy under ultra high vacuum. Bimodal size distribution of the islands are observed in 0.25-0.45 monolayer (ML) coverage: the bigger islands are formed at the elbows of the herringbone reconstruction, while relatively smaller sized Cr islands appear due to the distortion of the herringbone pattern by the islands formed at the bulged elbows. Further deposition results in increase of the island size with characteristic shapes. Eventually, the islands coalesce resulting in pseudomorphic growth of Cr layers showing (1×1) hexagonal low energy electron diffraction pattern similar to the substrate indicating that Cr grows pseudomorphically on Au(111). [DOI: 10.1380/ejssnt.2014.49]

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Transparent electrodes are widely used in touch panels, solar cells, displays and lighting devices. Developing materials to replace indium tin oxide (ITO) is accelerated from the viewpoint of cost and resources. We developed organic conductive films based on poly (3,4-ethylenedioxythiophene)-poly(styrene sulfonate). The ITO-free organic transparent electrodes were applied to polymer organic light emitting diodes (OLEDs). Solutions of the conductive electrodes and light emitting materials were spin-coated successively on transparent substrates, followed by vacuum deposition of cathode, LiF and Al. We found that the organic conductive films made a good electrical contact to metals, but poor contact (high resistance) with some organic conductors, e.g., conductive glues of conductive metal tapes. Making use of this property, we could construct OLEDs without patterning transparent electrodes (anode), unlike the widely used ITO electrodes which require patterning for device applications to avoid short-circuit. Because electric insulation is automatically made with our films, the device fabrication process will be drastically simplified. [DOI: 10.1380/ejssnt.2014.57]

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Quantifying the coadsorption of dye molecules on nanoporous TiO₂ is difficult because of the complex adsorption structure between the dye and TiO₂ surface. D131 dye absorbs strongly in the ultraviolet region and is a common co-sensitizer for dye-sensitized solar cells. In this study, we showed that Cl-terminated D131 dye coadsorbed with a Ru complex on nanoporous TiO₂ can be used as a labeling compound to quantify coadsorption systems by X-ray photoelectron spectroscopy (XPS). Cl-terminated D131 alone and Cl-terminated D131 and N719 coadsorbed on nanoporous TiO₂ were measured with XPS. The Cl atoms were quantified by the peak intensity ratio of the Cl 1s and Ti 2p peaks. In the Cl-terminated D131 + N719 coadsorption system, the amount of Cl-terminated D131 dye adsorbed decreased by about 44% for the 1:1 mixture. Our technique could also be used to quantify other dyes in co-sensitizer systems, such as black dye and N3 dye. [DOI: 10.1380/ejssnt.2014.63]

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Models of adatom surface diffusion and incorporation at the sidewalls of nanowires and 3D islands are proposed. The models account for the presence of an atomic step on the sidewall facet and for the adatom transport from the substrate to the sidewall. Peculiarities of the potential relief for migrating adatoms as well as the effect of step permeability are taken into account. It is shown that kinetics of the step propagation at the nanowire sidewall is affected by the presence of a strong sink for adatoms at the nanowire top facet and by adatom desorption from the sidewall. As a consequence, survival of the step at the nanowire sidewall depends strongly on the nanowire length. For 3D islands it is shown that the adatom concentration at the island apex can be considerable even in the absence of the deposition flux provided that the step is permeable for adatoms and there exists substantial material transfer from the wetting layer to the island facet. This favors formation of new steps at the island apex and may trigger the morphological transition of the 3D island. [DOI: 10.1380/ejssnt.2014.68]

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The crystal-structure deformation depending on lattice parameters in A^NB^8-N compounds is investigated on the basis of density-functional theory (DFT) calculations. Our DFT calculations for C, BN and BeO demonstrate that the energy difference in cohesive energy along crystal structure deformation path strongly depends on the ionicity 𝑓_i of materials. In particular, the energy barriers for structural deformation from threefold coordinated (hexagonal graphite) to fourfold coordinated (wurtzite) structures in BN and C are marked, whereas that in BeO is negligible. The difference in the energy barrier originates from both repulsive interaction among bond charges and attractive interaction among ionic charges. The repulsive interaction among bond charges in C (𝑓_i = 0) results in the highest energy barrier of 0.39 eV, while the attractive interaction among ionic charges in BeO with large ionicity (𝑓_i = 0.602) does in quite small energy barrier. These results imply that the ionicity is crucial for determining the energy change along crystal deformation path as well as the structural stability. [DOI: 10.1380/ejssnt.2014.79]

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The effects of high-temperature annealing on the properties of an Al₂O₃/InAlN interface formed by atomic layer deposition (ALD) is investigated by X-ray photoelectron spectroscopy (XPS). The interface between 2-nm-thick ALD Al₂O₃ and InAlN were annealed in N₂ at 800, 850, or 950°C. The shapes of the In 3d, In 4d, N 1s, and Al 2p core-level spectra were not changed by annealing, which indicated that significant intermixing was not induced at the Al₂O₃/InAlN interface by annealing at high temperatures of up to 950°C. The O 1s spectra consisted of two components for all samples. The higher-energy component in the O 1s spectra, which was reduced in intensity but not removed by annealing, was revealed to be localized at the Al₂O₃ surface. The Fermi level position at the InAlN surface was also investigated but no change was observed upon annealing at all temperatures. By also considering results of the electrical measurement, the absence of Fermi level pinning at the Al₂O₃/InAlN interface is discussed. [DOI: 10.1380/ejssnt.2014.83]

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Local structure of ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF₄), at IL + water mixtures / highly-oriented pyrolytic graphite (HOPG) interfaces has been investigated using frequency-modulation atomic force microscopy (FM-AFM). The imaging study of surface topography and energy dissipation of IL + water / HOPG interfaces suggested that even the hydrophilic IL molecules favored the HOPG substrate forming stable layers of ILs whose layer thickness corresponded to the averaged ion-pair size. A threshold molar ratio (χ_IL) for the first IL layer formation was between 0.01 and 0.05 and the HOPG surface was completely covered by IL layer at as low as χ_IL = 0.1. Force curve measurements in various concentrations of IL + water mixtures also suggested that the liquid side nature such as the apparent viscosity near the interfaces changed around the critical concentration. Dissolution of the IL layer was found to be a slow process, suggesting that the interface structure was history-dependent. Furthermore, electrochemical potential of the HOPG substrate affected the IL layer formation. Particularly application of positive potential resulted in growth of IL layer at the interface. [DOI: 10.1380/ejssnt.2014.89]

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We studied the metallization behavior of molecularly thin Ru_0.95O₂^0.2− nanosheets obtained from complete delamination of a layered ruthenate, K_0.2RuO_2.1. Heating at 200°C under a mixture of N₂ and H₂ transformed multilayers of the nanosheets into hcp-Ru metals. These metals have unique morphology reflecting the multilayer structure of the precursors. Interestingly, a monolayer state of the Ru_0.95O₂^0.2− nanosheets triggered a dot-like formation of Ru metal nanocrystals about 0.6 nm thick and several tens of nanometers wide, which represent a new family of 2D anisotropic metal nanomaterials. [DOI: 10.1380/ejssnt.2014.97]

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Structural and magnetic stability of Fe bilayer films on Cu(111) substrate was investigated from first-principles calculations, in which two atomic-stackings are considered for the fct-like and bct-like phases of the Fe bilayers. When a ferromagnetic (FM) alignment of the Fe bilayer is assumed, the surface Fe atoms energetically favor the bridge sites (bct-like phase) better than the hollow sites (fct-like phase). On the contrary, for an antiferromagnetic (AFM) alignment, the fct-like phase becomes favorable. The results suggest that the bi-stability of the FM and AFM structures may lead to the coexistence of the fct-like and bct-like phases observed in experiments. [DOI: 10.1380/ejssnt.2014.102]

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The present study performs production of copper oxide particles, and examines the particles as a filler in metal-metal bonding. Leaf-like aggregates with a longitudinal size of ca. 600-950 nm and a lateral size of ca. 280-380 nm, which were composed of particles with a size of ca. 10 nm, were produced with a salt-base reaction using a Cu(NO₃)₂ aqueous solution and an NaOH aqueous solution. Copper discs were bonded by pressurizing them, between which the particles were sandwiched, at 1.2 MPa for 5 min in H₂ gas under annealing at 400°C. Bonding properties of particles were evaluated by measuring shear strength, which was required to separate the discs. The shear strengths were as large as ca. 23 MPa at NaOH/Cu(NO₃)₂ ratios of 1.9 and 2.0, since CuO particles that contained nether Cu₂(OH)₃NO₃ nor impurity based on the addition of NaOH were produced at the ratios. [DOI: 10.1380/ejssnt.2014.105]

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To investigate electric-field-induced superconductivity in covalent semiconductors, band structures and induced-hole carrier density of hydrogenated Si(110) surface in an external electric field were calculated by using first principles full-potential linearized augmented plane-wave method. Results predict that the induced-hole carriers, which form a Fermi surface with a hole pocket centered at Γ point, are less than the critical density of superconductivity for boron-doped Si. Thus, electric-field-induced superconductivity at Si(110) surface may be difficult to achieve, which is in contrast to the case of diamond(110) surface. [DOI: 10.1380/ejssnt.2014.109]

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We investigate the electronic states of a simple model of a lipid bilayer membrane with a siloxane-bond-reinforced surface using first-principles calculations based on density functional theory. Our model is a simple representation of a cerasome, a material that has proved promising as a drug delivery medium. Analyzing the electronic density of states reveals that there is a mid-gap state originating from the Si-C antibonding state. The existence of an antibonding state at mid-gap indicates that we can selectively excite an electron to this state and thus break up the siloxane network. [DOI: 10.1380/ejssnt.2014.112]

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We present the electrical and thermal transport calculations through interface of metallic aluminum and semiconductor silicon materials. The obtained transport results are utilized to find the thermoelectric properties of Seebeck coefficient and figure of merits. We find that the increase of Seebeck coefficients and also the decrease of thermal transport due to the scatterings of electrons and phonons at the nanometer-size interface enhances the efficiency of thermoelectric energy conversion around the Fermi energy. [DOI: 10.1380/ejssnt.2014.115]

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Beam characteristics generated by vacuum electrospray of ionic liquids were investigated at gas pressures of 10^-5 Pa. An imidazolium ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl) amide (EMI-TFSA), and an ammonium ionic liquid, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl) amide (DEME-TFSA), were tested. Transient response measurements showed that m/z values of EMI-TFSA charged droplets were smaller than those of DEME-TFSA charged droplets under the same experimental conditions. The m/z values of EMI-TFSA charged droplets decreased with decreasing flow rate. A target current exceeding 30 nA was produced at a capillary voltage of 1.6 kV even with a low flow rate of 3 nL/min, at which the peak value of m/z distribution was 7.9×10⁴. The average mass, charge number and diameter of the charged droplets at m/z = 7.9×10⁴ were estimated to be about 6.1×10⁶ u, 77 and 23 nm, respectively. [DOI: 10.1380/ejssnt.2014.119]

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A novel single-molecule magnet (SMM) of trans-substituted Tb(III) porphyrin, {[Tb(BIPPP)₂](DBU-H)} (BIPPP: 5,15-bis(3,5-isopentoxyphenyl)porphyrin, DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene), is reported here. The alternating current magnetic susceptibility measurements showed the frequency dependence on the in-phase and out-of-phase magnetic susceptibility under both zero and 2000 Oe direct current magnetic fields. The barrier height for the reversal of the magnetic moment at the high-temperature region was estimated to be 299 cm^-1, which is the same order as that of the previously reported tetraphenylporphyrin-based Tb(III) double-decker complex. Atomic force microscopy revealed that {[Tb(BIPPP)₂](DBU-H)} formed self-assembled monolayers on highly oriented pyrolytic graphite using the simple drop-cast technique. The result proves the high design freedom of porphyrin-based double-decker SMMs. [DOI: 10.1380/ejssnt.2014.124]

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We investigated the surface structure and the local magnetic moment of Co clusters grown on a reconstructed surface of Au(111). We performed an in-situ experiment with scanning tunneling microscopy (STM) and soft X-ray magnetic circular dichroism (XMCD) spectroscopy, to reveal the spin and orbital magnetic moments on the Co atomic site in the well-characterized cluster structure without overlayers. While the spin magnetic moment is comparable to bulk Co, the orbital magnetic moment is considerably enhanced in the clusters whose lateral size is 8.4 nm. [DOI: 10.1380/ejssnt.2014.129]

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Besides my memories on Dr. Heini Rohrer, I discuss his contribution in the development of STM and nanotechnology. Toward the end of this talk, the view point of reductionist is also discussed. [DOI: 10.1380/ejssnt.2014.133]

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The formation processes of InN/GaN heterostructures on GaN(0001) substrate are investigated by means of our ab initio-based approach and Monte Carlo (MC) simulations. Our ab initio calculations reveal that even under Ga-rich conditions the pseudo-(1×1) surface consisting of In in the first layer and Ga in the second layer is more stable than that of Ga in the first layer and In in the second layer. Furthermore, the calculated surface phase diagrams demonstrate that the pseudo-(1×1) surface with In-Ga metal layers can incorporate 2.3 monolayers (MLs) of N atoms under growth conditions. The MC simulations using ab initio calculation data imply that both InGaN alloy and InN/GaN heterostructure can be formed depending on the growth conditions, consistent with the experimental results. On the basis of these findings, the stability of these structures is discussed in terms of the strain accumulation in the resultant structures. [DOI: 10.1380/ejssnt.2014.136]

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Five charged iridium(III) complexes with a different number and position of methyl group; [Ir(phen)(ppy)₂]PF₆ (1), [Ir(4-phen)(ppy)₂]PF₆ (2), [Ir(2,9-phen)(ppy)₂]PF₆ (3), [Ir(4,7-phen)(ppy)₂]PF₆ (4) and [Ir(4,5,6,7- phen)(ppy)₂]PF₆ (5) were synthesized and characterized by NMR, IR, UV-Vis absorption, fluorescence spectroscopy and cyclic voltammetry. The host-guest light-emitting electrochemical cells (LECs) based on ITO/PEDOT:PSS/1- 5:PVK (1:4)/Al were investigated, which resulted in a maximum current efficiency at 1.35 cdA^-1 and a brightness at 717 cdm^-2 from 5. The host-guest LECs can be improved by the insertion of the TPBi and LiF layers. We found that the highly efficient electroluminescence device gave the peak current efficiency to 4.49 cdA^-1, the maximum brightness at 1,200 cdm^-2 with Commission Internationale de L’Eclairage (CIE) coordinates of (0.30, 0.54) from 3. [DOI: 10.1380/ejssnt.2014.141]

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I describe my encounter with Rohrer sensei, with many thanks to him, through one touch, one drawing, and one word. [DOI: 10.1380/ejssnt.2014.149]

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My memories on Dr. Heini Rorher, especially those in 1980s and the early 1990s, are described. Then the future directions of the application of STM are discussed.
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We have performed atomistic calculations of phonon transport properties. The dynamical matrix is obtained from ab initio calculations, and phonon transport properties are analyzed by the nonequilibrium Green's function method. As an example of the applications of the method, we present the temperature dependence of heat transport properties and the phonon lifetime due to phonon-phonon scatterings by the anharmonic terms of interatomic forces for a silicon crystal. [DOI: 10.1380/ejssnt.2014.154]

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The atomic arrangements of zinc blende structured GaN_xAs_1-x-yBi_y thin films coherently grown on GaAs(001) substrates are theoretically investigated using empirical interatomic potentials and Monte Carlo simulations. The resultant atomic arrangements of GaN_xAs_1-x-yBi_y strongly depend on N composition x and substrate lattice parameter a_sub. It is found that the incorporation of N atoms in GaAsBi results in the formation of layered structures consisting of GaN, GaAs, and GaBi regions. This is because Ga-N interatomic bonds tend to be located around Ga-As interatomic bonds to approach its equilibrium bond length. Furthermore, either GaBi or GaN surface segregation appears to reduce the strain caused by lattice constraint. These results suggest that the miscibility of GaN_xAs_1-x-yBi_y thin films can be controlled by choosing suitable lattice constraint varied by x and a_sub that approach the bond length of the equilibrium values for semiconductor material. [DOI: 10.1380/ejssnt.2014.171]

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The electronic structure of Ni₂P(10-10) has been investigated by angle-resolved photoemission spectroscopy (ARPES) utilizing synchrotron radiation. The surface prepared by Ar⁺ ion sputtering (3 kV, 15 min) and annealing (400°C) gave a c(2×4) low-energy electron diffraction pattern. The ARPES measurements on this surface showed that there were at least three surface states. One was observed at about 0.4 eV around the Γ point, and the state was found to be formed in a (1×1) region which is coexistent with a c(2×4) region on the surface. The other two states were observed in the vicinity of the Fermi level around the Γ point and at about 0.6 eV at k_∥ ≥ 2 nm⁻¹ along the [-12-10] direction. These states grew with the progress of segregation of P atoms, and were assigned as the states formed in the c(2×4) region. [DOI: 10.1380/ejssnt.2014.175]

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