Ce doped germanium dioxide nanowires with cubic GeO₂ and tetragonal CeGeO₄ phases have been synthesized by the hydrothermal route using sodium dodecyl sulfate (SDS) as the surfactant. The nanowires have the length and diameter of about 20 μm and 50–200 nm, respectively. The SDS assisted growth process is proposed to explain the formation of the Ce doped germanium dioxide nanowires. Ce doped germanium dioxide nanowires is used as the photocatalyst for the photocatalytic degradation of gentian violet (GV) under solar light irradiation. The roles of the solar light irradiation time, content of the nanowires and GV concentration on the photocatalytic degradation of GV are investigated. GV can be totally degraded under solar light irradiation for 240 min using 15 mg nanowires in 10 mL GV solution with the concentration of 10 mg · L⁻¹. The Ce doped germanium dioixde nanowires show good application potential for the removal of organic pollutants under solar light irradiation. [DOI: 10.1380/ejssnt.2016.4]

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We have numerically investigated the effects of light scattering by silver nano-particles on the surface protection sheet of an amorphous silicon solar cell. The structure consists of two silver nano particles, a protection sheet, an indium tin oxide layer, and an amorphous silicon solar cell. Two silver nano-particles are put on the protection sheet of the solar cell. The larger diameter of silver nano-particles increases the transmission intensity of the structure at the peak wavelength of 417 nm. The appropriate gap between two silver nano-particles on the protection sheet of the amorphous silicon solar cell increases the transmission intensity of the structure compared with that of the solar cell with less gap at the incident light wavelength of 554 nm. [DOI: 10.1380/ejssnt.2015.83]

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SnO₂/ZnO nanorod composite photocatalysts have been successfully fabricated via combining the electrochemical deposition (ECD, for ZnO nanorod) with a simple solvothermal growth (for SnO₂ nanoparticle). As was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), SnO₂ nanoparticles in a tetragonal phase were attached on the side faces of ZnO nanorods to form the nanocomposites. SEM and TEM images indicated that the diameter and the length of the SnO₂/ZnO nanorod composites were 100–300 nm and 2–5 μm, respectively. The effect of ECD potential on the microstructure of ZnO nanorobs was also investigated. The observation of the morphologies showed that the optimum spacing of ZnO nanorods grown on Cu substrates were obtained when ECD potential was −0:8 V at 80°C. The photocatalytic behavior of the SnO₂/ZnO nanorod composite photocalysts has been examined by monitoring the photodegradation of rhodamine B (RhB) under UV-radiation exposure. SnO₂/ZnO nanorod composites showed higher photocatalytic activity toward photodegradation of RhB than bare ZnO nanorods, which was due to the efficient charge separation at the SnO₂/ZnO composite photocatalyst interface. [DOI: 10.1380/ejssnt.2016.136]

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The investigation of adsorption behavior of Basic Green 4, a basic dye was carried out using multi-walled carbon nanotubes (MWNTs) and nano porous activated carbon materials prepared from Turmeric Industrial Waste (TWAC) as the adsorbents in the batch mode contact time process with respect to initial dye concentration (20, 40 and 60 mg/L), temperature (303,318 and 333 K) and pH. The surface area and pore size volumes for the TWAC and MWNTs were estimated by nitrogen adsorption measurements at 77 K. The morphology of the carbon samples were studied by scanning electron microscopy. A comparison of kinetic models applied to adsorption of Basic Green 4 on both TWAC and MWNTs were evaluated for pseudo first-order, pseudo second-order and Elovich models respectively. Results prove that the pseudo second order kinetic model was found to correlate the experimental data well for both adsorbents. Langmuir and Freundlich adsorption isotherm studies were also measured. The film and pore diffusion kinetics were studied to propose plausible mechanism for the adsorption of Basic Green 4 dye using both multi-walled carbon nano tubes (MWNTs) and nano porous activated carbon materials prepared from Turmeric Industrial Waste (TWAC). [DOI: 10.1380/ejssnt.2016.165]

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ZnO nanoparticle (NP) layers were formed using a simple drop casting process. Applying thermal pressing clearly improved the surface morphology and electrical properties of the as-deposited ZnO NP layers as well as significantly enhanced the transistor characteristics of the NP layers. The effects of thermal pressing on the film surface properties were evaluated by X-ray photoelectron spectroscopy, Kelvin probe microscopy, and photoluminescence spectroscopy. Results suggest that thermal pressing improved the transistor characteristics by decreasing NP surface defects such as oxygen vacancies. [DOI: 10.1380/ejssnt.2016.175]

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Composite paper containing single-walled carbon nanotubes (SWNTs) has been employed for artifact-metrics authentication using Raman mapping images for authentication keys. To make the most of SWNT properties for authentication, it is desirable to use the diversity of chiralities for authentication keys. In this study, we explored the application of photoluminescence (PL) imaging of SWNT-composite paper to artifact-metrics authentication. SWNTs were wrapped with carboxymethyl cellulose to activate PL and embedded in paper. PL mapping images of different chiralities were examined for authentication. The authentication accuracy was greatly improved by using three-chirality keys. An estimated error rate as small as 10^－12 was achieved. [DOI:10.1380/ejssnt.2016.185]

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The present research demonstrates a procedure for surface modification of Highly Oriented Pyrolytic Graphite (HOPG) electrodes intended for use as immunosensors. The HOPG surface is linked to the molecule 8-hydroxydeoxyguanosine (8-OHdG), an oxidative stress biomarker for DNA damage, though the aniline mediator covalently bonded to electrode and biomarker. An electrochemical procedure to graft the mediator is described and the presence of biomarker at surface is demonstrated by using a fluorescence-labeled immune-reagent. An electrochemical functionalization process has been employed for attachment of functional aminie (NH₂) linking groups to graphitic surfaces, which consists of two stages: (i) a reaction with a diazonium salt to covalently bond nitrobenzene groups to the surface and (ii) electrochemical reduction of the nitro group (–NO₂) to an amine group (–NH₂). The shape of the CV curve indicates that the redox reactions are taking place at the HOPG electrode surface. The amine group can subsequently be used to covalently link to an antibody biorecptor. The presence of 8-OHdG, indicative of DNA damage, has been linked to increased cancer risk. Detection of this oxidative stress biomarker is an important tool for the early diagnosis of disease. [DOI: 10.1380/ejssnt.2016.193]

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We observed cement/sandstone interfaces after reaction with supercritical CO₂ using SEM-EDS, μ-XRD, and μ-Raman spectroscopy in order to evaluate chemical reactions of well-cement in CO₂ storage site. To model actual well in geological formation, we prepared a well composite sample consisting of steel casing, Portland cement, and Berea sandstone. The batch experiment was performed for 56 days under a condition of 10 MPa and 50°C. After the batch experiment, a carbonation zone appeared at the cement/sandstone interface, however, the carbonation depth was limited within a few millimeters and the inner part of the cement was not altered. The Ca concentration in the carbonation zone increased 13% in comparison to that in the unaltered cement zone while the Mg, Si, and S concentrations decreased significantly. The predominant crystalline phases in the carbonation zone were calcite, aragonite, and vaterite. In addition, sparse precipitation of CaCO₃ was observed in the pore spaces of the sandstone along the cement/sandstone interface. [DOI: 10.1380/ejssnt.2016.198]

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Anisotropy of atomic-scale peeling of the monolayer graphene sheet adsorbed onto the graphite substrate surface is numerically studied by molecular mechanics simulation. During the peeling process the surface contact area of the graphene sheet takes atomic-scale sliding behavior, which strongly depends on the initial contact orientation angle θ_in between the graphene sheet and the graphite surface within the lateral plane. When the initial contact is commensurate AB stacking orientation (θ_in = 0°), the mean lateral force during the peeling process takes a maximum peak value. However, as the initial orientation angle θ_in increases (0° < θ_in ≤ 30°), the effect of the incommensurate contact is further enhanced, and the mean lateral force decreases toward near zero value. At an intermediate incommensurate angle (θ_in = 9°), the peeled area of the graphene sheet twists around the perpendicular axis during the peeling process since the surface contact area discretely slips toward metastable AB stacking orientation. The above anisotropic sliding mechanics of the graphene sheet appeared during the peeling can be applied to the mechanical control of the material properties of the π-conjugated sheet as a novel device. [DOI: 10.1380/ejssnt.2016.204]

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In this study, pristine and calcined activated clay (AC) were characterized by scanning electron microscopy, X-ray diffraction analysis, thermogravimetric-differential thermal analysis, electron probe microanalysis, surface pH measurement, specific surface area measurement, and humidity adjustment. ACs were used as adsorbents for investigating the adsorption kinetics, isotherms, thermodynamic parameters, of Basic Red 46 (BR), Basic Blue 75 (BB), Acid Red 138 (AR), and Acid Blue 185 (AB) in aqueous solutions, as well as the effect of sodium hydroxide on these dyes. The results showed that adsorption of cationic and anionic dyes was related to the specific surface area (0.974–0.984) and humidity adjustment performance (0.939–1.000), respectively. The adsorption capacity of the cationic dyes (BB and BR) onto pristine AC increased on increasing the temperature. Equilibrium data using pristine AC fitted well to both the Langmuir and Freundlich isotherm models. Kinetic data were best described by the pseudo-second order model (correlation coefficient was 0.979–0.999 and 0.945–0.999 for BB and BR). Nearly 8 h of contact time was sufficient for the adsorption of cationic dyes to reach equilibrium. Thermodynamic parameters were also evaluated for the cationic dye-adsorbent system, which revealed that the adsorption process is endothermic in nature. These results demonstrated that pristine AC could be used as a natural adsorbent for the removal of cationic dyes (BB and BR) from aqueous solution. [DOI: 10.1380/ejssnt.2016.209]

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An atmospheric-pressure argon (Ar) plasma jet was generated with a frequency of 10 kHz, an applied voltage of 10 kV, and an Ar gas flow rate of 10 L/min. When an aluminum (Al) thin film deposited on a glass substrate was irradiated with the Ar plasma jet in air for 5 s, Al was removed. The removal rate was ∼700 nm/s. Because the streamers in the plasma reached the Al thin film, Al was removed and a mark was formed on the film, which was referred to as a removal mark. The shape of the removal mark depended on the irradiation distance: it was ring-shaped with an inner diameter of ∼5 mm and an outer diameter of ∼6 mm for irradiation distances of 2–7 mm, and disc-shaped with a diameter of ∼5 mm for irradiation distances of 10–20 mm. The dependence of the shape of the removal mark on the irradiation distance suggests that the distribution of the streamers in the plasma depended on the irradiation distance. The streamers inside the quartz tube were concentrated along the inner wall. In contrast, the streamers outside the tube were distributed in a ring shape with an inner diameter of ∼5 mm and an outer diameter of ∼6 mm for irradiation distances of 2–7 mm, but they converged then diverged to form a smaller disc shape with a diameter of ∼5 mm for irradiation distances of 10–20 mm. [DOI: 10.1380/ejssnt.2016.231]

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Photoelectron diffraction is an effective method to analyze element-specific atomic structures of surfaces. Recently, the Two-dimensional photoelectron spectroscopy (2D-PES) end station at the soft x-ray beamline BL25SU, SPring-8 was upgraded. Few-10-μm diameter focused beam is now available for measuring poly-crystalline and small crystalline samples. We show a series of photoelectron diffraction patterns from gold poly-crystalline surfaces mapped in two dimensions at an interval of 20μm. The sample surface position was two-dimensionally scanned and the best crystalline quality position was searched for the measurements of full-hemisphere photoelectron diffraction patterns and spectra. [DOI: 10.1380/ejssnt.2016.59]

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Scanning tunneling potentiometry (STP) is one of the advanced variations of scanning tunneling microscopy (STM). By combining STM and STP, the local structures and potential distribution on conducting samples with a lateral current flowing along the sample surface can be measured simultaneously with a high spatial resolution. However, additional electrodes are necessary to make the current flow along the sample surface, which can sometimes be difficult to handle. We developed a new type of STM tip holder that makes it easier to perform in situ STM/STP measurements in ultrahigh vacuum (UHV), prepare a sample and transfer the sample/tip. Using this tip holder, a Si(111)-√3×√3-Ag surface and Bi(111) films grown on Si(111) were measured using STP. For the Si(111)-√3×√3-Ag surface, abrupt potential drops at the atomic steps in the topographic images are observed. On the other hand, for the Bi film, a nearly homogeneous potential gradient is observed along the direction of the electric current without potential drops at the steps on the surface. By combining numerical simulation and atomic-scale resolved STM images, it is shown that the current distribution is not homogeneous at all, even at nanometer scales. This is due to a wide range of scatter in the resistances across steps, irrespective of the step height. This originates from difference in the ratio of the conductivity at the steps to that on the terraces between the two material systems. [DOI: 10.1380/ejssnt.2016.216]

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Measuring tiny interatomic forces between tip and sample has been an important challenge in the development of atomic force microscopy (AFM). Present force sensitivity achieved by a frequency modulation (FM) technique allows us to obtain atomic resolution routinely using FM-AFM. We applied the capability to measure the chemical bond between two atoms to identify the chemical species on surfaces. The chemical bonding force can also be used for single atom manipulation at room temperature. Recently, these AFM capabilities have led to the creation of various artificial nanostructures atom-by-atom, such as atomic clusters. By AFM characterization combined with scanning tunneling microscopy (STM), we found that some clusters work as atomic switches, which can be controlled by atomic force as well as carrier injection. [DOI: 10.1380/ejssnt.2016.28]

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In the field of nuclear fusion technology, Er₂O₃ thin film is a candidate for the coating material of the blanket of thermonuclear fusion reactor. It is known that the luminescence of Er₂O₃ provides information on its crystallinity. We observed luminescence of various samples including Er₂O₃ during the irradiation with highly charged ions produced by an electron beam ion source (EBIS) as a function of charge state and kinetic energy of incident Ar ions. We found that the luminescence intensity non-linearly rises as the charge state increases and is independent of kinetic energy. This demonstrates that the luminescence arises from the potential energy of highly charged ions rather than the kinetic energy. Emission spectra from various samples indicate that emission from sputtered atoms, mostly atomic hydrogen, is remarkable, while emission lines from the surface layers due to transitions among Stark splitting were observed for Er₂O₃ samples. [DOI: 10.1380/ejssnt.2016.1]

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n-GaN crystals were plasma-etched with N₂ gas, and their surfaces were analyzed mainly by X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS). In the samples etched with a high self-bias voltage of −400 V, the surface morphology changed, roughening under the treatment conditions of higher gas pressures (∼100 mTorr) and longer treatment times (∼200 min). In these samples with a roughened surface, the N/Ga composition ratios measured by XPS deviated greatly in the Ga-rich direction from the normal N-preferentially etched sample. Moreover, N-K near-edge X-ray absorption fine structure (NEXAFS) spectra changed greatly from that normally observed in GaN crystals. New peak features were also observed in the O 1s XPS and the O-K NEXAFS spectra. The surface roughening, the composition deviation, and the anomalous spectra in XPS and the NEXAFS correlated well with each other, which indicated the formation of another compound in the surface-roughened sample. [DOI: 10.1380/ejssnt.2016.9]

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An enhancement of current of field-ionized He from a W⟨111⟩ gas field ion emitter in mixtures with Ne or Ar and its origin were investigated by a field ion microscope equipped with a time of flight (ToF) spectrometer. He ion current was increased up to three times by He-Ne mixture and two times by He-Ar mixture, respectively. Mass to charge ratio spectra show that only He atoms were field-ionized at a field of operating condition of a He gas field ion source. In both gas mixture conditions, a peak of singly charged He in ToF spectra shifted after the mixture of He and Ne or Ar, which corresponds to that He was field-ionized at lower potential energy. These observations indicate that He atoms field-adsorbed on a tungsten surface are exchanged for Ne or Ar atoms and the exchange of species of field-adsorbed atom is also related to the enhancement of He ion current. [DOI: 10.1380/ejssnt.2016.23]

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We developed a fluorescence XAFS system toward operando conditions using soft x-ray radiation at KEK-PF BL-27A. X-ray adsorption fine structure (XAFS) analysis in the soft x-ray region is useful for elucidating molecular structures in both atmosphere and solutions. Particularly, light elements play an important role in many cases in this energy region. The attenuation of soft x-rays in a solution is large compared to that of hard x-rays. Thus, appropriate spectral statistics cannot be obtained in the soft x-ray region. Recently, using fluorescence XAFS measurement at the S K-edge (2.4 keV), we found that biological molecules containing sulfur atoms adopt specific molecular structures under different pH conditions in a solution. However, the diameter of the beam of this beam line at BL-27A was large, leading to difficulties in uniformly irradiating only the sample surface. Therefore, it was necessary to uniformly irradiate samples using a small-area x-ray beam. To collimate the beam and improve its intensity, we installed an x-ray focusing device. Herein, we introduce a light-collecting device that uses a polycapillary x-ray lens to focus soft x-rays. After installing this lens, we confirmed that focused x-rays and a higher-intensity beam were achieved. We conclude that focusing x-rays using a polycapillary lens in the soft x-ray region is an effective method for obtaining better spectral statistics in fluorescence XAFS measurements. [DOI: 10.1380/ejssnt.2016.35]

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We have demonstrated in situ and real-time-resolved X-ray absorption ne structure (XAFS) observation for oscillatory creation and removal reactions of surface oxide layer of Pd and Cu metal nanoparticles during cyclic flow of oxidative and reductive gases every 10 s. Pd and Cu K-edges XAFS spectra were collected at about 1-2 Hz. Precise observation of edge position was utilized for monitoring surface oxidation and reduction reactions. Reaction rate of surface oxide layer creation by NO for Pd metal nanoparticle is faster in the case of H₂/NO cyclic flow than in CO/NO. Fast and two-step surface oxidation and reduction reactions were revealed in Cu metal nanoparticles. [DOI: 10.1380/ejssnt.2016.48]

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Boron-doped diamond (BDD) films have good electrochemical performance with a wide potential window and chemical stability in aqueous solutions, compared with other electrode materials made of Pt, glassy carbon, and so forth. BDD electrodes have been investigated for various industrial applications, such as ozone-dissolved water and effluent water treatment. In this study, to achieve a high synthesis rate of BDD films, trimethyl borate was additionally introduced to a hot-filament chemical vapor deposition (HF-CVD) system as a reactant gas. It was found that the growth rate and quality of diamond prepared using the HF-CVD system depended on the effect of CH₄ concentration on hydrogen, distance from filament to substrate, and supply B/C ratios. BDD films with a high growth rate in the range from 2 to 4 μm/h have been obtained at a filament-to-substrate distance of 5 mm, a CH₄ concentration of 4%, and B/C ratios of 0.3-2.0%. Cyclic voltammograms of a Pt and BDD electrodes in 0.2 M KNO₃ have been investigated in terms of the effect of supply B/C ratios of 0.3, 0.5, and 2.0%. It was found that BDD electrodes had a wide potential window and a low background current compared with conventional Pt electrodes. The BDD films prepared and characterized in this study are efficient as electrodes for environmental applications. [DOI: 10.1380/ejssnt.2016.53]

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Physically adsorbed gas molecules have dramatic effects on the inherent properties of 2D nanomaterials due to their atomic/molecular-level thinness. In this work, we applied laser THz emission spectroscopy to study the gas adsorption-desorption dynamics of tungsten disulfide (WS₂) nanosheets prepared by liquid phase exfoliation technique. We find that in low vacuum conditions, NIR irradiation promotes desorption of O₂ molecules from WS₂ nanosheets. Upon exposure to atmospheric air, results suggest slight photo-oxidation caused by NIR irradiation. Strong photo-oxidation by UV illumination is also confirmed, and we also observed subsequent O₂ desorption from WS₂ nanosheets by NIR irradiation when the UV illumination is turned off. These results are discussed using the Langmuir adsorption isotherm, which explains the variation of gas adsorption with the gas pressure. [DOI: 10.1380/ejssnt.2015.78]

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We investigated the thickness distribution of gold particles sputtered by a focused ion beam (FIB) and deposited on a section perpendicular to the irradiated surface. The calculation results were analyzed from the viewpoint of three-dimensional metal-assisted secondary ion mass spectrometry (3D MetA-SIMS), a novel method that uses sputtered metal particles to enhance the signal yield of organic samples. The calculated distributions showed characteristic shapes of deposited gold, which had both a steep area and a flat area. The former area can be used for determination of sputtering feature, and the latter area can be used as the target area in which the sample section is located. The amount of particles on the target area was calculated to be within a reasonable range, implying that 3D MetA-SIMS can be realized with this simple and reasonable process. In summary, we established the foundation for enhancing the scope and effectiveness of 3D MetA-SIMS. [DOI: 10.1380/ejssnt.2015.87]

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Sample degradation of LaNiO₃ ultrathin films on SrTiO₃ (001) substrate caused by air exposure is examined by means of crystal truncation rod (CTR) scattering method. Although the film is conductive right after the sample deposition, long term storage makes it insulating. CTR measurements were performed on three- and four-unit cell-thick samples just after the sample deposition and after six months of storage in air. The results show that the storage induced a signicant increase in the lattice spacing along the surface normal direction with keeping in-plane periodicity. Such a structural change can be caused by escaping oxygen atoms by the thermal uctuation. [DOI: 10.1380/ejssnt.2016.14]

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Molecular spintronics aims at exploiting and controlling spin-dependent transport processes at the molecular level. Achieving this aim requires not only appropriate molecules, molecular structures and preparation procedures. Equally important is the understanding and engineering of the electronic and spin-dependent interactions between different molecular species, molecule and substrate, as well as molecule and electrodes. These interactions may not only determine the spin-dependent functionality of the molecular structures, but also their integrity on the substrate. Likewise, there may be also a modification of the surface properties below and in the vicinity of a molecule. We have investigated several molecules on different metallic surfaces, among them magnetic Nd double-decker phthalocyanines, a cubane-type {Ni₄} complex with single-molecule magnet properties, and a nonmagnetic triazine-based molecule. For NdPc₂ molecules adsorbed on a Cu(100) surface, our scanning tunneling microscopy and spectroscopy studies show specific electronic states of the molecule-substrate complex. We find that the electric field between STM tip and sample must be taken into account to properly describe the electronic states associated with the upper Pc ligand. [DOI: 10.1380/ejssnt.2016.17]

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Chemical vapor deposition (CVD) of graphene was investigated by using an in-situ reflection high-energy electron diffraction (RHEED). A Si wafer covered with a 150 nm thick of SiO₂ was used as a substrate, on which a 100 to 600 nm thick of metal (Cu, Co, Ni) was deposited as a catalyst (Cu is known as a metal with low carbon solid solubility, Co and Ni are known as metals with high carbon solid solubility). The substrate was heated up to 900°C and 0.1 Pa of ethanol was introduced as a source gas, and the RHEED pattern was monitored during the CVD process. As the result, a streak pattern, which was originated from 2-dimensional graphene, appeared immediately after the start of the growth for all kinds of catalysts. It was also revealed that the streak appearance time depends only on catalyst material, but not depends on their thickness. Therefore, even on the high carbon solid solubility catalysts, it was considered that graphene nucleation occurred directly on the catalyst surface without solution-segregation process of carbon atoms. [DOI: 10.1380/ejssnt.2016.39]

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Scanning tunneling microscopy investigation is performed on a nitrogen(N)-adsorbed Cu(001) surface. Grid-like nanopattern of 4-fold symmetry is well-known on N/Cu(001), where square N-islands of the size, ca. 5 nm × 5 nm, are aligned along both [100] and [010] directions. We find for the first time a ribbon-like nanopattern in a region vicinal toward [100] with a long-annealed specimen. In the vicinal region, parallel steps run along [010], and each (001) terrace is so narrow as to accommodate only a single N-island in width. These N-islands are aligned perpendicular to the steps, resulting in a ribbon pattern. Closely-spaced parallel steps lower surface symmetry locally from 4-fold to mirror. We ascribe the ribbon pattern to the lowered symmetry. N-islands in the ribbon are changed to rectangles, in marked contrast with squares in the grid. We discuss the square-to-rectangle deformation by considering the shearing strain between the topmost N-adsorbed layer and the second Cu layer. [DOI: 10.1380/ejssnt.2016.43]

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The surfaces of steel specimens after dipping in a solution with or without tungstate addition, followed by a corrosion test, were investigated by various techniques, e.g., cross-sectional Cs-(S)TEM, SEM and XPS, to gain an improved understanding of the role of tungstate in corrosion resistance. The corrosion reaction during the test was drastically suppressed when tungstate was added. A crystalline film approximately 4 nm thick consisting of Fe and O was formed on the surface after dipping in the solution without tungstate. After dipping in the solution with tungstate, a film consisting of Fe, O and W was formed with the thickness of about 4 nm. The latter film consisted of two layers; the outer layer showed lower crystallinity and a higher W concentration. This film improved corrosion resistance. It is supposed that (1) barrier properties are improved by the low crystalline layer or (2) W⁶⁺ in the film inhibits the corrosion reaction. The WO₄^2- in the solution also protected the surface during the test. When the ultrathin film is destroyed, WO₄^2- reacts with iron ions eluted from corrosion pits to form thicker protective films and pit propagation is also suppressed by segregation of W⁶⁺ in the corrosion products above pits. [DOI: 10.1380/ejssnt.2016.63]

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Voltage pulse which has been used from the establishment of atom probe (AP) in the 1960's is going to be replaced by short pulsed laser with high repetition rate in the nanometer scale characterization of materials by 3D-AP. Scanning Atom Probe (SAP) has a miniature electrode for acceptance of non-needle shaped specimens which allows us to analyze non-solid materials which are common in chemistry. The selectivity and the adaptability of voltage pulse and laser pulse are not clear in the non-bulk materials which are common in chemistry but not familiar in AP field. Two types of trigger, voltage pulse and laser pulse, were applied alternately to the identical sample to perform direct comparison. Tungsten tip, conventional material in AP, and amino acid (L-Tryptophan) supported on carbon nanotube were chosen as candidates for this analysis. The dual trigger system successfully worked on metallic sample and the selectivity of the ion species and adaptability were demonstrated on molecular system. [DOI: 10.1380/ejssnt.2016.69]

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We have theoretically studied the azimuthal angular dependance of surface and bulk plasmon losses in Al 2s photoemission spectra. Here, full multiple scatterings of photoelectrons are taken into account before and after plasmon losses within the quantum Landau formula, which can describe overall features of the photoemission bands. By considering elastic scattering, the azimuthal angular dependence can be evaluated. Two types of peaks are observed; strong peaks attributed to forward focusing and weak peaks appeared as diffraction pattern. Forward focusing peaks are observed when atoms exists in the forward direction. The peak intensities from deeper layers are reduced by the defocusing effect. The origin of the weak peaks are discussed with the local geometric analysis. The differences of main, 1st bulk and surface plasmon loss are discussed.The peaks of diffraction pattern largely changed by increasing the photoelectron kinetic energy. [DOI: 10.1380/ejssnt.2016.73]

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Anomalous behaviors of Auger intensities have been observed for ZnO(0001) surface depending on the glancing angle of incident electron beam of RHEED. In the beam rocking Auger electron spectroscopy, BRAES, the profiles of Zn(LMM) and O(KLL) were compared with each other. It was found that their profiles differed in some aspects. This suggests that their Auger intensities are influenced by the wave field of incident electron beam of RHEED. In this study, RHEED rocking curves were also measured and analyzed by dynamical calculations. It has been found that the determination of surface polarity is possible by RHEED rocking curves. [DOI: 10.1380/ejssnt.2016.92]

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Considerable attention is currently being given to nanotip electron sources. These have a number of desirable emission characteristics, including high current density at low voltage, a small source size leading to high coherency, and narrow confinement of the electron beam. To date, we have developed a high-precision energy analyzer capable of obtaining the emission spectrum of the electrons emitted from a nanotip electron source. To improve the resolution of the analyzer, we design an optimum energy analyzer electrode and a more stable power supply. Moreover, the beam current measurement circuit is needed to facilitate the adjustment of the optical axis. Therefore, we have also developed a computer-controlled power supply with low noise, low ripple, and stable output voltage, together with a current measurement circuit and its associated software. [DOI: 10.1380/ejssnt.2016.97]

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A Si-covered 6H-SiC(0001) surface was transformed from a Si-rich to C-rich one with increasing annealing temperature. An alkali metal is well known for promoting oxidation. We studied the oxidation to Cs pre-adsorption on a 6H-SiC(0001)-(3 × 3) reconstructed surface using metastable-induced electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), and low-energy electron diffraction (LEED). The (3 × 3) reconstructed surfaces was adsorbed Cs and exposed oxygen at room temperature. The MIES results show that the intensity of electron emission induced Cs6s increased with Cs evaporation. For the oxygen-exposed Cs/SiC surface, the emission intensity of the Cs6s-induced peak rapidly decreased and a dissociated adsorption oxygen-induced peak appeared. When the oxygen-adsorbed Cs/SiC(0001) surface was annealed until 800°C, Cs atoms were desorbed from the surface and O bonded with Si, forming SiO₂. [DOI: 10.1380/ejssnt.2016.103]

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We performed first-principles energy-band calculations based on the generalized gradient approximation (GGA) in the Perdew-Burke-Ernzerhof (PBE) functional to determine the electronic structure of the graphene/SiC (0001) interface with a √3 × √3 SiC periodicity. In the calculations, a structural model of graphene on a 4H-SiC substrate was constructed using a slab that contained four bilayers with dangling bonds terminated by hydrogen on the another surface of the slab. It is well known that the GGA method tends to overestimate the graphene layer spacing (GLS) when compared with experimental values reported previously. We included van der Waals interactions in the present calculations with the PBE-GGA exchange-correlation functional using the Grimme and Tkatchenko-Scheffler methods. The former scheme was observed to well reproduce the experimental value of the GLS compared with the latter one. Finally, the influence of Si and C vacancies on the electronic structure of the graphene/4H-SiC (0001) interface was investigated using these methods. [DOI: 10.1380/ejssnt.2016.107]

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Atomic structures and electronic states of epitaxial graphene on the SiC(11-20) a-face are studied based on the first-principles calculation. It is found that the surface can have two types of the surface, the stable quasi-free-standing structure and the quasi-stable buffer layer structure. The neutral nature, the low interface state density, and the absence of large interface dipoles suggest that the epitaxial graphene on the SiC(11-20) a-face is appropriate for studying the physical properties of carrier transport. It is also proposed that the existence of the buffer layer is directly related with the epitaxial relation of the formed graphene with the SiC substrate. [DOI: 10.1380/ejssnt.2016.113]

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We used scanning tunneling microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy to investigate the influence of ion-beam irradiation on the growth of graphene on 3C-SiC(111) surfaces via the SiC surface decomposition method. When the SiC(111) surface was irradiated with Ar⁺ ions, the surface bonds of the SiC(111) surfaces were broken. After annealing the SiC surface with an Ar⁺-ion beam at an accelerating voltage of 1 keV and an incident angle of 70°, we obtained graphene with few defects. However, in the case of Ar⁺-ion-beam irradiation at 60°, the resulting graphene layers exhibited high defect concentrations. We observed that the Si defect and breakage of bonds in the surface region promotes the formation of graphene layers and that the destruction of the deep layers of SiC substrate prevents the growth of graphene. [DOI: 10.1380/ejssnt.2016.121]

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The certified reference material (NMIJ CRM 5206-a) is composed of a Si substrate with homogenously doped arsenic, and multiple alternately deposited boron nitride (BN) layers and Si layers. The designed thicknesses of the Si and BN layers were 8 nm and 0.05 nm, respectively. The thickness of each layer was measured using X-ray reflectometry (XRR), and the periodicity of the distance between the delta BN layers was determined to be 8.3 nm. The expanded uncertainty was 0.2 nm and was calculated using a coverage factor (k) of two that gives a level of confidence of approximately 95%. The concentration of the As atoms in the Si substrate, measured by instrumental neutron activation analysis (INAA) and inductively coupled plasma-mass spectrometry (ICP-MS), was determined to be 0.80 g/kg with an uncertainty of 0.04 g/kg (k = 2). For the calibration of the developed reference material, three institutes with two types of secondary ion mass spectrometry (SIMS) instruments derived the SIMS depth profiles of the implanted arsenic atoms. The results were compared, and it was observed that the relative standard deviation (RSD) of the profile parameters was approximately 10%. [DOI: 10.1380/ejssnt.2016.125]

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In recent years, the needs of mass spectrometry for biological samples have rapidly increased. In this study, in order to analyze water-containing biological samples using time-of-ｆｌight secondary ion mass spectrometry (TOF-SIMS), a rapid-cooling method, sectioning system, and a sample introduction method that could avoid frost formation in plant biological samples were developed. It was confirmed that both frost formation and evaporation of volatile compounds were prevented by a rapid-cooling and new introduction method. Essential elements and H₂O could be detected by this new rapid-cooling TOF-SIMS methodology. Therefore, SIMS analysis in the natural state became possible. [DOI: 10.1380/ejssnt.2016.131]

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Metal phthalocyanines (MePc) have unique features applicable to the field of electronics and optics. In this study, we observe the surface electronic structure of MePc (Me = Cu, Zn) adsorbed Si(100) using metastable-atom induced electron spectroscopy (MIES). MePc molecules are deposited for less than 2000 s in vacuum at room temperature. At the initial adsorption of the MePc, each molecule lays flat on the substrate and the center metal atom is on top. This orientation of the adsorbed molecules gradually changed with an increase in the deposition time of the MePc. When the MePc covered surface was annealed by direct current heating at 800°C or below, the molecules started to decompose and desorbed from the Si(100) surface. However, Cu atoms remained on the surface. We discuss the adsorption structure based on the deposition time and behavior of the MePc molecule with annealing. [DOI: 10.1380/ejssnt.2016.141]

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We obtained HEED patterns for water cluster beams, which showed the cubic structure that is characteristic of ice. The intensity of the (111), (220), and (311) diffraction peaks increased with an increase in the vapor pressure. As an extension of the water cluster studies, a methane hydrate cluster was generated by a gas bubbling method. In addition, the fundamental phenomenon of water cluster ion irradiation was studied using photoluminescence measurements. The cluster ion beam-induced luminescence was observed, and the luminescence intensity increased with an increase in the acceleration voltage. This indicated that the kinetic energy was converted to thermal energy and the cluster temperatures as well as impact area could be very high. Furthermore, polymer substrates such as poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), and polycarbonate (PC) were also subjected to irradiation by the water cluster ion beams, and the sputtered depth increased with an increase in the acceleration voltage. In particular, the sputtering yield of the PMMA surface was 206 molecules per ion at an acceleration voltage of 9 kV. Compared to the PET and PC surfaces, extremely high sputtering yield was obtained owing to the chemical modification of the PMMA surface by water cluster ion irradiation. [DOI: 10.1380/ejssnt.2016.144]

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Mg nanoparticles covered with the Pd nanoparticles (Pd/Mg NPs) have been fabricated by the gas evaporation method using He gas. The coaxial formation of the Mg and Pd NPs enables to fabricate the Pd/Mg NPs. The surfaces of the Pd and Mg NPs are quite clean because only pure He gas has been used during the fabrication of the NPs. The surface and interface chemical states of the Pd/Mg NPs have been investigated by X-ray photoelectron spectroscopy (XPS) without the exposure to the air. The XPS investigation has revealed that the formation of the interfacial alloy state between the Mg and Pd NPs. The Pd/Mg NPs can absorb the hydrogen at the room temperature by the hydrogenation of the most of the Mg atoms inside the Pd/Mg NPs. [DOI: 10.1380/ejssnt.2016.150]

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It is important to study the distribution of host and guest molecules in organic electroluminescence materials because their distribution dramatically affects the functionalities of these materials. In order to understand this distribution, a new analysis method should be developed to obtain sub-nanometer scale information. In this regard, we used Atom Probe Tomography (APT). APT is a three-dimensional analysis technique with sub-nanometer scale resolution and is frequently used in material science and engineering. There are many reports on the analysis of inorganic materials using APT analysis, however only a few studies report the analysis of organic materials because of difficulties in the sample preparation, measurements, and the three-dimensional reconstruction of organic materials. In this study, we focused on developing a new sample preparation method and suggested the new sample preparation method for the analysis of organic materials. This new preparation method needs only a small amount of organic materials for analysis. Moreover, it is very simple and combines electrolytic polishing with the dipping method. [DOI: 10.1380/ejssnt.2016.154]

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Inverse x-ray fluorescence holography provides new knowledge about the local atomic structure around dopants in crystals. The three-dimensional atomic image is reconstructed from the inverse x-ray fluorescence hologram using a calculation. The performance of the algorithm used for this calculation is important. The Barton method, which is based on the Fourier transform, is typically used. However, images reconstructed by this method sometimes contain artifacts. I developed an algorithm (SPEA-L1) using an iterative method with L₁ regularization and report its performance. [DOI: 10.1380/ejssnt.2016.158]

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We developed a mass spectrometer with a novel mass-separation mechanism using two rotating electric fields (REFs). This mass spectrometer realizes a wide mass range with the continuous separation of ion beams. In principle, it has no limitation on the mass range. It can be operated stably for the detection of high-mass ions. To estimate the mass-separation ability, we directly introduced the mass spectrometer, which consists of two REFs, to a Ga focused ion beam column. The mass spectra of Ga isotopes were obtained by sweeping the frequencies of the REFs. The peaks of the Ga isotopes were clearly separated on the mass spectra. [DOI: 10.1380/ejssnt.2016.161]

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In the shave-off method, which combines an X-axis sweep with a much slower Y-axis sweep, the sample is completely etched using a Ga focused ion beam (FIB). One advantage of this method is the higher axial resolution obtained because of sputtering by the edge of the FIB. Recently, our group developed a two-dimensional (2D) shave-off method and 2D data acquisition was achieved. This method enables the analysis of curved interfaces, such as transistors, by determining the analytical axes after the measurement. In the shave-off method, the axial resolution along the Y-axis has been studied, but the X-axial resolution has not been studied. In this study, we analyzed the X- and Y-axial resolutions using experimental measurements and simulations. The axial resolution was revealed to be anisotropic by measurement of an alumina particle, and further analyses were performed by simulating the etching process. The X-axial resolution of the shave-off scan was suggested to be similar to that of a raster scan. A simulation of the shape of the shave-off cross-section showed that the anisotropic axial resolution was caused by etching with the whole width of the FIB along the X-axis, except during the last sweep before complete etching of the sample. Calculation of FIB profiles using the Lorentzian function suggested an approach for improved high-resolution 2D shave-off measurements. [DOI: 10.1380/ejssnt.2016.179]

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Atom probe tomography (APT) is a three-dimensional (3D) analysis technique with atomic resolution in materials science and engineering. The ionized atoms are sequentially released from the surface of the sample with needle shape by applying high voltage and are detected by the position-sensitive detector. The original arrangement is reconstructed using reconstruction parameters such as the image compression factor and the field factor from recorded data during measurement. It is crucial to the integrity of the reconstruction to estimate the reconstruction parameters as accurately as possible. However, it is difficult to determine the reconstruction parameters accurately due to sequential change of the shape of the sample during measurement. In this study, by using FEM we propose a new reconstruction method that the reconstruction parameters can be determined even during the measurement. [DOI: 10.1380/ejssnt.2016.189]

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Groove patterns on the surface of implants act as an effective barrier to the apical migration of epithelial attachment, after which the grooves facilitate gingival fibroblast attachment. Cell alignment on grooves is largely influenced by the adsorbed protein type. However, cell attachment and cell alignment properties of micro/nano-grooved dental composite resins using osteoblasts and fibroblasts have not been investigated. Further, the effect of saliva-related protein adsorption has not investigated. In this study, we prepared composite resins with grooves that were 2 μm, 1 μm, and 500 nm wide and estimated the effect of pre-coating of some proteins, mainly mucin, on attachment and alignment of human gingival fibroblasts(HGF). In the cell attachment assay on mucin-coated grooves, the number of attached cells on mucin-coated planar or grooved composite resins was lower compared to that on both composite resins without pre-coating of mucin. Interestingly, the number of attached cells on grooves pre-coated with mucin was 5.7-fold higher than those on planar pre-coated with mucin. Grooves at the micro/nano level may act as a hook for floating cells during the cell attachment assay. Furthermore, the degree of cell alignment was strongly dependent on the pre-coating protein types. The cells were radially spread or round-shaped, but not have sufficient alignment on non-, mucin-, and albumin-coated grooves. Although the cells were attached on the grooves, they were not aligned along the direction of grooves. The cells on fetal bovine serum- or fibronectin-coated grooves exhibited good alignment in the groove direction, particularly on fibronectin-coated grooves. Thus, our patterning method creates an effective seal between soft tissue and dental materials to protect against microorganism invasion. [DOI: 10.1380/ejssnt.2016.225]

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