Here we report the AFM observation for T phase of silicene on Ag(111).All the constituent Si atoms including the lower-buckled ones are successfully resolved by high-resolution AFM imaging.The observation results identified the detailed atomic structures of T phase.

Because organic heterointerfaces govern operational mechansims of organic devices such as photovoltaics, investigating formation mechanism of the interface at molecular scale is essential. In this study, employing scanning tunneling microscopy, we observed structural disordering upon formation of perfluorinated copper phthalocyanine/sexithiophene (6T) interface. Comparison experiments suggested that (i) flexible conformation of 6T, (ii) heteromolecular interaction, and (iii) matching of molecular sizes led to the complete disordering observed.

Observation of low-energy positron diffraction patterns with a linac-based slow-positron beam

Silicon (110) surface has a unique one-dimensional “16×2” reconstructed structure with up-and-down terrace. We have succeeded in in-situ observation of strain/stress evolution on the Si (110)- “16×2” surface during adsorption of hydrogen atoms. Anisotropic strain/stress properties in the Si(110)-“16×2” surface are determined by contrast with hydrogen-terminated Si(110) 1×1 surface.

Because of their interesting magnetic properties, iron nitrides have attracted great attention. We have investigated square iron nitride monatomic layers on Cu substrates. A square iron nitride monolayer was fabricated even on the threefold symmetric Cu(111) substrate. In the present study, we will report a new hexagonal iron nitride film on Cu(111). We will compare the structure and electronic property of the hexagonal iron nitride film investigated by using LEED-IV and STM.

The structural transformation and conductive properties in alloy nanocontacts during pulsed-voltage energization, which has not been investigated, was analyzed in situ by transmission electron microscopy. TiNi was selected as the target composition.

Si protrusions with the metal cap were epitaxially grown as liquid phase epitaxy on the rectangular Si(111) pieces by DC resistive heating at around 1300 °C under an applied tensile stress. The Fe or Cu were deposited on Si(111) surface before the epitaxial growth. The cap of the protrusion with Fe deposition was a Fe-Si alloy, but there was no Cu-Si alloy on the protrusion with Cu deposition. The intentionally deposited metal Fe diffused via electromigration and precipitated into the cap.

The study to calculate the characteristics of gas flow has not been completed yet. The points that makes the calculation difficult are; (i) The characteristics of gas flow change depending on the pressure and so on. (ii) The phenomina which is not sufficiently understanded such as gas scattering on the engineering surface are related. (iii) Calculating not only gas flow and pressure distribution but also other quantities (heat, friction, force, etc.) is required. (iv) The collaborations with the other calculation such as cemical/plasma reations are requred. Five speakers who are studying these problems are introduced.

In a micro/nanoscale gas flow, interesting phenomena like velocity slip, thermal creep and Knudsen force, which cannot be seen in usual flow, appear. I am engaged in researches to analyze such phenomena and clarify their characteristics with the aid of numerical simulations. In this lecture, I will introduce my researches.

Two decades have passed since numerical simulations were applied to analyze rarefied gas flows in semiconductor device manufacturing equipment, e.g., plasma etching and PECVD reactors. Today, various simulation technologies are practically utilized, sometimes coupled with plasma simulation, for research, development, and improvement of equipment. In the meeting, we present several simulation examples thus far and also the latest research, DSMC on COMSOL with quasi-Nanbu scheme.

We studied a pumpdown curve in the low and medium vacuum regimes for a conductance-limited pumping. Senda [H. Senda, SEI Technical Review 176 (2010) 1.] predicted that an exponential decrease of the chamber pressure, followed by a reciprocal behavior with time near the lower limit of the viscous flow. He proposed a pressure boundary between the exponential decrease and the reciprocal decrease as a “Bifurcation pressure”. We experimentally found bifurcation pressures and they quantitatively compered with the theoretical estimation. The result of our experiment agreed fairly well with values that had been obtained by the theoretical calculation. We will discuss expletive effects such as turbulent flow at the initial stage of pumpdown and intermediate flow effect at the middle to low vacuum regimes.

The surface effect to the gas flow in a vessel cannot be ignored. The scattering from the surface has been studied for a long time as a major subject. In this paper, I will introduce the understanding at present of atomic and molecular scattering from surfaces.

We have a problem that the surrounding oxygen and water vapor leak through defective pinhole(s) of a sealed package. If the gases on both sides of the package wall are equal in total pressure but there is a difference between the gas concentrations, diffusion causes gas movement. We analytically determine the amount of gas diffusion passing through each of the two models of a shallow hole and a deep hole, and compose these models to obtain a gas diffusion.We report the derivation of the equation for calculating the amount of gas diffusion in a cylindrical hole having a predetermined depth.

In the carrier conduction of an N-type organic semiconductor, the molecular state is switched between the neutral state and the negative ion state. In order to correctly understand the carrier conduction, both electron affinity (A) and electron detachment energy (D) are essential. Although (A) has been studied in detail using Inverse Photoelectron Spectroscopy, there has been no effective way to observe D in the solid phase. In this study, we succeeded in the observation of D by performing Operand-Photoelectron Yield Spectroscopy (PYS) for an organic transistor in which electrons can be injected by gate potential.

Recently, great progress has been made experimentally in angular distribution measurement of photoelectrons, and the momentum map (MMP) of photoelectrons emitted from molecules adsorbed on a substrate has come to be accurately measured. Pushnick et al., reported that these data shown isolated molecular orbitals. The presenter reports the result based on the multiple scattering method and the DFT with respect to multi-body information contained in MMP.

Despite the exceptional photocatalytic effect of TiO₂ nanotubes, the photocatalytic reaction process on TiO₂ nanotube surface has seldom been studied. In this work, by directly fabricating ordered TiO₂ nanotube arrays on Si prism, we have investigated photocatalytic reaction on TiO₂ nanotube surface using infrared absorption spectroscopy in the multiple-reflection geometry (MIR-IRAS). The in-situ observation results revealed that the O₂ is more effective than H₂O in promoting the photocatalytic decomposition of organic materials using TiO₂ nanotubes. By comparing the reaction photodecomposition of organic materials on TiO₂ nanotubes with that on TiO₂ nanoparticles, we demonstrated that TiO₂ nanotubes are superior in photocatalytic reactivity to nanoparticles.

Infrared absorption of molecules adsorbed on nanostructured surfaces is enhanced, which is known as surface-enhanced infrared absorption (SEIRA). To date, SEIRA has been thought to occur on metal surfaces, but infrared abosorption enhanced has also been observed on nanostructured silicon surfaces. We will talk about this result.

Plasmon-enhanced Raman spectroscopy has attracted considerable attention as a highly sensitive label-free biosensing technique. Here in this study, the gap size between two metallic nanorods is optimized to maximize plasmonic field enhancement at the gap in the visible region, enabling us to achieve single biomolecular detection.

We found that methyl-thiophenol (MeTP) and mercaptobenzyl alcohol (MBAl) molecules at a nano gap between silver nanoparticles and silver films are oxidized to mercaptobenzoic acid (MBA) under a weak laser irradiation. This oxidation is not induced by plasmonic heating but by hot carrier such as electrons and hole. We confirmed these using heating experiments up to 373 K, and the intensity ratio of Stokes and anti-Stokes shift of MeTP indicating only modest heating of the samples less than 10 K during the oxidation. We also found that this reaction is not site selective for MBAl but selective for MeTP, relating to the reaction mechanism. Also we observed intermediate species between MeTP and p-MBA under nitrogen flow, while faster oxidation under oxygen flow.

Solid electrode/solid electrolyte interfaces in all-solid-state batteries are recognized as one of the most critical parts for power density and durability. In order to understand the ion/electron transport properties across the interfaces, the change of elemental composition and electronic structure at the interfaces should be observed in the operational condition. In this research, we developed an operando X-ray photoelectron spectroscopy system for analyzing the elemental composition and electronic structure under application of voltage, and then applied to the thin-film batteries for investigating charge/discharge reactions.

Tip-enhanced Raman scattering (TERS) spectroscopy, which utilizes the nanoscale localized light generated in the vicinity of a metallic tip apex, has attracted much attention as one of the powerful surface analytical tools. In this work, we succeeded in inducing the trans-cis isomerization reaction of an azobenzene derivative directly under the tip apex by locally applying external stimuli such as pressure and voltage to the molecule, which was in-situ observed through the TERS spectral changes.

Ionic liquids have been expected as new electrolytes that have both high functionality and safety because of its unique characteristics such as wide electrochemical window, extremely low vapor pressor, and high thermal stability. Recently, electronic excitation spectra of various ionic liquids in 150-450 nm range were measured using our original attenuated total reflectance far-ultraviolet spectroscopy. Additionally, a new electrochemical system was introduced into the spectrometer, and potential dependences of ATR spectra for interfacial ionic liquids on electrodes were investigated.

Organic light-emitting materials have been studied for many years both in terms of basics and applications centering on photochemistry. In particular, much attention has recently been focused on the utilization of the excited triplet state of organic compounds, and studies on molecular design and thin film structure to overcome small spin-orbit interaction of light elements are in progress. In this presentation, we will introduce recent research on next-generation organic light-emitting materials such as thermally activated delayed fluorescent materials, together with our efforts and research results using laser spectroscopy technology.

Nanoscale stress presented in biological materials plays an important role in human health. For example, stress produced by extracellular matrix in a mammalian cell transfer mechanical cues to nucleus to control cell behavior. It is therefore highly desirable to measure quantitatively small stress with high spatial resolution, especially under operando conditions. AFM uses a nanoscale tip to sense the local forces directly from specimen. However, to quantitatively measure local stress from a force spectrum, we must know the exact physics model for the specimen-tip interaction for a material system and the exact geometry of the AFM tip during operation. We developed a data-driven objective way of accurately determining the physical model and AFM tip geometry in operation, so that an informatics-AFM system could be realized to quantitatively measure nanoscale local stresses in various material systems. Application example will be studying the stress state in a living cancer cell in liquid. Such capability could lead to a mechanobiological way of automatic identification of cancer cells so that easy diagnosis of cancer at early stage becomes possible.

We developed time-resolved electrostatic force microscopy with tip-synchronized pump-probe method. Using this method, carier generation and transport in organic solar cells, polimer conductors. We obtained the infromation of photogenerated ion-pair generation and recombination, and polaron conduction.

Our group has proposed a machine-learning method to analyze force mapping measured using a noncontact atomic force microscopy. In force map of Si (111)-(7x7), we extract a short-range force part contributing to atomic resolution, and then analyzed long-range components after the subtraction. It has been found that long-range components include not only van der Waals forces that do not contribute to atomic resolution but also information that seems to be the effect of AFM tip asymmetry.

Molecular imprinted polymer (MIP) on a micro-cantilever can be used for protein sensing. OV Albumin sensing was performed from the strain evolution of MIP caused by capturing the target molecule in solution. We report the combined results of stress measurement, weight (resonance frequency) measurement, and hardness measurement were combined to evaluate the cause of strain generation and the reliability.

We have developed an X-ray aided non-contact atomic force microscope (XANAM) that combines NC-AFM and synchrotron radiation X-rays to study chemical analysis of sample surfaces at the nanoscale. We previously reported that a change in force signals could be induced around the Ge-K X-ray absorption edge energy on a Ge sample surface under X-ray irradiation. In this report, force volume measurements as an expansion to imaging were performed based on the previous result. We will report the results on a surface of Ge single crystal and Ge quantum dots as samples.

We investigated a relation between the surface potential on aluminum alloys by KFM and its corrosion resistance .Surface potential difference between matrix and intermetallic compound of the aluminum alloy which has less corrosion resistance was bigger than that of higher corrosion resistance aluminum alloy. This was the same tendency as corrosion potential measured electrochemically. Measurement of surface potential by KFM is useful to reveal corrosion phenomenon because this method has higher resolution than the electrochemical method.

In site-specific force spectroscopy, force sensitivity is enhanced by reducing the oscillation amplitude of the sensor. A quartz length-extension resonator (LER) offers the advantage of small-amplitude operation by virtue of its ultra-high stiffness. The high spring constant of LER enables us to perform AFM at oscillation amplitudes as low as 100 pm. Here, we demonstrated that an LER can accurately measure short-range interatomic forces. Since the effective stiffness of an LER has not been estimated, we derived a formula for calculating the effective stiffness of an oscillating LER by using the theory of elasticity. We found that the obtained dynamic stiffness was 1.23 times greater than the static stiffness.

Computational model for friction force microscopy (FFM) is proposed and it reproduces the sawtooth-like modulation of the cantilever as observed in the FFM experiment. The motions of atoms on the surface are calculated using molecular dynamics method and macroscopic motion of the cantilever is described by oscillation of a spring. These two models are concurrently coupled in the FFM model, which enables us to obtain the details of atomic behavior on the surface as well as the modulation of the cantilever and the energy dissipation of the friction.

Recently, 3D atomic force microscopy (3D-AFM) has been developed, which has enabled to image the solid/liquid interfacial structures directly with sub-nanometer scale resolution. In this study, we have developed low-latency wideband components for 3D-AFM and improved the scanning speed by 10 times without deteriorating its atomic-scale resolution. In addition, we succeeded in the direct imaging of the dynamic changes in the hydration structures at dissolving step edges of calcite (CaCO₃) in water at 5 sec/3D images.

The brightness of image spot in Field Ion Micrograph (FIM) is directly affected by field ionization yields on each surface atom site. By using the field evaporation technique to extract a surface atom from the predetermined site, we have measured the changes of image brightness at each atom site in the vicinity of the field evaporated atom, and have examined the variation of ionization yields as well as the peak position with maximum magnitude of brightness within a single image spot. The results show that the peak position with maximum magnitude of brightness moves toward the direction of field evaporated atom core.

We have observed a spatial variation of a field ionization yield in a step edge on a W surface using a micro-probe hall field ion microscope, and derived a spatial distribution of a tunneling barrier field from the spatial variation of the field ionization yield. The tunneling barrier field distribution presents a local high field, especially above a single W atom. A direction and strength of a spread of the field distribution quantitatively provides a magnitude and a range of field enhancement formed by a field adsorption on surface atoms.

A topological insulator (TI) having ferromagnetism (FM) induces an energy gap at the Dirac point of the surface band by breaking time reversal symmetry. In addition, when the Fermi level (E_F) is tuned within the gap, the quantum anomalous Hall effect (QAHE), which possesses the dissipation-less current circulating along the edge of the sample in the absence of external magnetic fields, is realized . In previous works, the QAHE was observed only at extremely low temperature due to the inhomogeneous FM order, low crystallinity, and the low Curie temperature (T_C). In the present work, we have successfully fabricated the high quality FM/TI heterojunction MnTe/(Bi,Sb)₂Te₃, whose E_F is tuned within the gap and T_C is above room temperature, for the higher temperature of observing the QAHE. The detailed data containing magnetic and electrical transport measurements will be presented.

We have studied the atomic structure and phase transition of a dense metallic monolayer of In on Si(111). Although the phase was previously considered to have a (√7×√3) periodicity, it was found to have a uniaxially incommensurate structure along <1-10>, by means of LEED, STM and first-principles calculations. We also observed a phase transition to a (√7×√7) phase at around 250 K upon cooling. ARPES and four-point-probe conductivity measurements demonstrated that the transition induces disappearance of metallic surface states and a sharp drop in sheet conductivity, respectively. These results indicate an electronic metal-insulator transition.

Si(111)-(√7×√3)-In is an atomic-layer superconductor with a critical temperature of 3 K. Our low-temperature electron transport measurements strongly suggests that the parallel upper critical field exceeds the paramagnetic limit expected for a conventional superconductor. We investigate the mechanism based on the pair-breaking theory for a superconductor in the presence of both the Rashba effect and elastic scattering, utilizing the information of the band structure obtained from density functional theory calculations.

The Rashba effect, which cause spin-slitting in a system without inversion symmetry, has been investigated in various materials for future spintronic applications. In this contribution, we will report our observation of quantum number dependent spin-splitting in quantum well states in Ag/Au(111) by spin-resolved photoemission. In addition, we found by DFT calculations that this behavior can be well explained by the quantum number dependence of the charge density distributions in the quantum well states.

We have performed time-resolved and angle-resolved photoemission spectroscopy for monolayer Cu₂Si on Si(111) substrate to confirm whether there is a nodal-line-like band dispersion. As a result, we found that Cu₂Si/Si(111) has a nodal-line located at ~0.3 eV above E_F by synchrotron-radiation ARPES and by time-resolved ARPES. At the presentation, we will show the details of experimental results and discuss the origin of the band dispersion as compared with Cu₂Si on Cu(111) substrate.

A theory of localized bulk and surface plasmons for metal nanostructures in dielectrics is derived in the random phase approximation at the high frequency condition. The induced charge density in dielectrics is added to the induced charge density by the plasmons in the integral equation for the scalar potential. The equation is composed of the local electron density in metal nanostructures, the local electric susceptibility of dielectrics. Using a model where the local dielectric functions have step function shapes at the interfaces between the metals and dielectrics, it can be analytically solved in the quasi-static approximation. The localized surface plasmon frequencies and the light emission intensities are then derived for metal nanostructures such as ultrathin layer, nanowire and nanosphere.

Recently, Bi(110) ultra-thin films have attracted much interests as a candidate for two-dimensional topological insulator. In our study in terms of the atomic and electronic structures of Bi ultra-thin films on Si(111)√3×√3-B substrates revealed that the Bi(110) islands preferencially grow as even-layer height islands with black-phosphorus-like structure whereas minor odd-layer height islands have a structure different from bulk-like structure.

Bimetallic phosphide NiFeP is a promising catalyst for hydrodesulfurization. The origin of the high catalytic performance of NiFeP is expected to arize from metal-metal interaction between Ni and Fe atoms. We tried to construct Ni_xP thin films by depositing Ni atoms on Fe₂P(10-10) to investigate the interaction of Ni and Fe atoms at the interface. The film covered surface showed a clear c(2×2) low energy electron diffraction pattern. From the analyses of Fe 3p and Ni 3p x-ray photoelectron spectra and resonant photoelectron spectra of valence band the electronic structures of Ni 3d and Fe 3d states are deduced to be hybridized.

We study the origin of high catalytic activity of transition metal phosphides compering Fe₂P which shows the lowest catalytic performance with Ni₂P which shows highest catalytic performance. We found 7 components of P atoms at the surface by the Photoelectron spectroscopy measurement. The surface composition of these components changed by annealing temperature. Furthermore, previously, we reported that stabilization of valence band maximum peak of Ni₂P occurred with increasing the annealing temperature, however, such stabilization did not find in the valence band spectra of Fe₂P.

High voltage operation for achieving high energy density is a next research direction of all-solid-state batteries with sulfide solid-electrolytes. In this study, we fabricated film-batteries consisted of layered rocksalt type cathode and sulfide solid electrolyte to elucidate interfacial phenomena at high voltage regions. Depth-resolved X-ray photoemission spectroscopy and in situ X-ray diffraction clarified the structural changes at the model interfaces. We will discuss a crucial factor that determines the rate-determining step and reversible charge-discharge reaction during high voltage battery operation.

In fluoride shuttle battery using the shuttle of fluoride ions, the transfer reactions of fluoride ions between electrode and electrolyte is proceeded during the charge and discharge reactions. The electrolyte should contain fluoride ions. However, when it is assumed that the using of organic electrolyte, inorganic fluoride salts are generally insoluble to organic solvents. The solubility of fluoride salts is improved by the addition of anion acceptor in the electrolyte. In this presentation, we report the effect of the anion acceptor on the electrode reactions.

We experimentally observed that the electric-double layer capacitance of a MXene electrode depends on the cation species intercalated into the electrode. This phenomenon was not observed with activated carbon electrodes. To understand this phenomenon, we simulated on the electric-double layer formed at the interlayer of the electrode by computer simulation combining the classical liquid theory and first-principles calculation. As a result, we revealed that the density of intercalated water depends on the cation species, and the water hydrating around cations exhibits negative dielectric characteristics accordingly, which enhances the electric-double layer capacitance.

The cationic species, such as Li⁺, strongly interact with adsorbed hydroxide and water, and the formation of stable layer within adsorbed species inhibits the electrode reactant on the surface. Therefore, it is important to investigate the hydration structure in order to understand the effect of cation on the electrode reactions. In this study, we reproduced the electrode surface including OH, H₂O and Li, on Pt(111) under ultra-high vacuum condition, and investigated the hydration structure by using infrared spectroscopy.

Direct methanol fuel cells are considered to be the next generation of small power supplies. However, it is difficult to obtain stable power output because the generated bubbles of carbon dioxide in the flow channel obstructs power generation of the fuel cell as it becomes smaller. To solve this problem, we propose carbon dioxide bubble emission method by hydrophobization of the channel surface. A micro structure was formed on the optical film using a thermal transfer method, and hydrophobic with a contact angle of about 136 ° was imparted. When the hydrophobic film was contained in the fuel channel, the number of air bubbles of 250 μm or more in diameter in the channel was reduced by about 57%.

It is known that the addition of fluoroethylene carbonate (FEC) to the solvent of the lithium ion battery of Si negative electrode, improves the performance of the battery. However, the detailed reason is not known. In this presentation, we will determine the structure and composition of Li-Si alloy which electrochemically formed by Li insertion in FEC solvent and discuss the effect of HF in the solvent.

We investigated hydrogen transport properties in nanocrystalline titanium nitride (TiN) using first-principles calculations based on density functional theory. We focused on the hydrogen transport in the grain boundary regions of nanocrystalline TiN, because TiN has dense rock salt structure. We unraveled that the TiN(100)/TiN(100) grain boundary realize low activation barriers for hydrogen diffusion. Corresponding activation barriers are lower than that of Pd which is widely used as hydrogen separation membranes. On the other hand, the TiN(111)/TiN(111) grain boundary shows much higher activation barriers for hydrogen diffusion. These results indicate that grain boundary engineering with nanocrystalline TiN can realize the alternative precious metal hydrogen separation membranes.