Photoelectron holography is a related method to XPS. It provides a three-dimensional atomic arrangement of the chemical state of each core level. The atomic arrangements such as dopants in crystal, interfaces under the surface, and so on can be measured. To measure photoelectrons at a wide steric angle, we have developed a retarding-field electron energy analyzer. It can measure a wide range of steric angles of ±50° with a high energy resolution. We also developed the theories of data analysis. These apparatus, theories, and applications will be introduced.

The photoelectron momentum microscope is a projection-type multifunctional photoelectron analyzer that combines an electron energy analyzer and a photoelectron microscope. Taking advantage of the feature that the field diameter in the momentum space can be expanded up to Ø6.4 Å^-1, it is possible to measure the band dispersion from a minute area of several μm size selected in the microscopic mode. At the UVSOR soft X-ray beamline, we launched the first experimental station for photoelectron momentum microscopes outside Europe. In this talk, we will introduce actual measurement examples.

Adhesion is an interfacial phenomenon that is a critical technology for assembling carbon structural composites for next-generation aircraft and automobiles. Despite this importance, we have a limited understanding of adhesion down to the molecular level because of the difficulty in revealing the individual multiple bonding factors. Using soft X-ray spectromicroscopy, we show the physical and chemical states of an adhesive interface. We observed multiscale phenomena in the adhesion mechanisms, which provide a benchmark for further research to examine how physical and chemical states correlate with adhesion.

In order to improve the efficiency of crystalline silicon solar cells, the factors that deteriorated the conversion efficiency were evaluated using hard X-ray photoelectron spectroscopy (HAXPES). In particular, evaluation of characteristic deterioration factors related to transparent conductive films used in SHJ solar cells. New carrier selective contact materials such as titanium oxide (TiO_x) and transition metal dicalgogenide (TMD), which is a two-dimensional layered material.

Real-time observation of absorption and desoption processes of hydrogen in palladium-gold alloys was performed by means of ambient-pressure X-ray photoelectron spectroscopy. We succeeded AP-XPS measurements in the presence of nitrogen gas at a pressure of 100 mbar using a newly developed apertrure nozzle. With the improved apparatus, we conducted AP-XPS experiments of the Pd-Au alloys in hydrogen, and detected changes in the chemical states of Pd and Au in the alloys related to a metal-hydride phase transition.

In order to realize a water splitting process using renewable energy, a water splitting catalyst with high oxygen production efficiency is desired. In this study, we developed the water splitting catalyst by crushing manganese carbonate minerals in a ball mill, and measured the XAFS spectra for it. XAFS analysis showed the occurrence of structural distortions on the surface of the minerals after crushing. Therefore, the developed mineral catalyst was guessed to function as reaction sites due to the structural distortion on the surface generated by crushing.

In recent years, material development has been promoted in a short period of time, and multifaceted reliability has been regarded as a problem. In the field of surface analysis as well, reliability in the entire flow of measuring equipment, specimen preparation, measurement, and data processing becomes an issue. The elements of reliability in measurement are organized as 3Rs (repeatability, reproducibility, reproducibility). Based on this, the Surface Analysis Research Division introduced the progress of measurement and data processing using the latest equipment, and planned an opportunity to discuss standardization in surface chemical analysis.

Hard X-ray Photoelectron Spectroscopy (HAXPES), which uses higher-energy X-rays than conventional photoelectron spectroscopy (X-ray Photoelectron Spectroscopy: XPS) using Al Kα (1486.6 eV) and Mg Kα (1253.6 eV), is drawing attention as one of the methods for evaluating the buried interface, which is a usually important factor that determines the device performance. Especially in recent years, laboratory-based HAXPES (Lab. HAXPES) has been developed and is being widely used in addition to synchrotron radiation facilities. Liquid Ga Kα (9251.74 eV) is used as the excitation light source to ensure stable and high intensity. In this presentation, we will introduce some measurement examples and discuss about the future prospects in various fields appropriate for Lab. HAXPES.

We have developed a novel XPS system integrated with an environment cell, a bias application module and a non-air exposure sample transfer vessel for in situ/operando measurements of liquid samples, solid/liquid and solid/solid interfaces using a conventional laboratory-based apparatus. A few examples such as quantitative detection of solution species and reaction analysis of electrochemical lithiation/delithiation of a silicon negative electrode deposited on a solid electrolyte will be presented.

In recent years, Near Ambient Pressure XPS (NAP-XPS) has been attracting attention as a method to analyze samples such as fuel cells and catalysts under conditions close to those of actual operating environments. SPECS Surface Nano Analysis GmbH has developed EnviroESCA as an instrument that can be deployed at the laboratory level. In this talk, we will report the features of the system in detail with actual measurement results.

For the analysis of XPS spectra dataset with many spectra, such as the initial oxidation process of GaN, which is registered in the Research Data Express (RDE) dataset of NIMS-DPFC. We attempted to perform automatic peak analysis of XPS spectra in the dataset. We have tried to analyze the spectra in two different ways, including Bayesian information criterion (BIC) analysis, and principal component analysis (PCA), and target factor analysis (TFA). From the results of these analyses, we report the oxidation trends of GaN, each surface, and each gas species.

We introduce the spectrum adapted EM algorithm as a method for high-throughput analysis of spectral data. In this presentation, we explain the theoretical background of the spectrum adapted EM algorithm and introduce examples of its application to a synthetic spectral data and an experimental spectral data collected by XPS. Moreover, we introduce an advanced method of the spectrum adapted EM algorithm based on the ECM algorithm. Using this advanced method, we demonstrate recent works for the background subtraction and optimization of the number of decomposed peaks in the peak fitting of spectral data.

Standardization in the field of surface chemical analysis is discussed in International Organization for Standardization/Technical Committee 201 (ISO/TC 201). In this talk, trends of standardization of surface chemical analysis in ISO/TC 201, especially, activities in sub-committee 4 (SC4) (depth profiling) and SC7 (electron spectroscopy), in which the author is mostly involved, are introduced.

ISO/TC201/WG4 is a working group for the surface characterization of biological materials, whose international convener was Prof. Setou since 2018, followed by the presenter this year. We will report on the recent progress of surface chemical analysis for biological materials, focusing on the imaging mass spectrometry (TOF-SIMS and MALDI), together with the needs of standardization.

I would like to consider the direction of tribology research in the society such as SDGs and green innovation.

It is common knowledge that there are two types of solid friction: "static friction" and "kinetic friction". However, the authors have found that through mechanical analysis of a sliding system with a geometric asymmetry, the rotation of the kinetic friction vector produces apparent static friction. From the point of view of this "dynamic stiction mode", using only purely mechanical terms, "stick-to-slip transition" can be described as "overdamping-to-underdamping transition".

Frictional force on material surfaces in atmosphere varies with relative humidity. Although this humidity dependence is generally rationalized by the condensation of adsorbed water to the contact area, molecularscopic description of the condensation is unclear. Furthermore, it is still under debate whether the adsorbed water before applying the frictional force forms uniform film on the material surfaces or not. For describing the relationship between the water condensation and the frictional force under atmospheric conditions, it is important to clarify at first the condensation structure of the adsorbed water before applying frictional force at molecular scale. In the present study, we analyzed the structural changes of adsorbed water with varying the relative humidity on silica, which is one of the typical hydrophilic materials, by surface-selective vibrational spectroscopy.

Against the background of global environmental problems, there is a need to develop friction reduction technology for machine elements. This investigation focused on the frictional interface structure of ionic liquids is highly dependent on the state of the friction surface. As an experimental method and result, this investigation have succeeded in active control of the friction coefficient in an attempt to control the adsorption structure of ionic liquids by externally inputting an electric potential to the friction surface.

Water lubrication has received considerable attention not only due to the importance as the fundamental mechanism of low friction in biological lubrication but also due to the benefits for energy efficiency and low environmental burden in machinery (from the SDGs standpoint). The excellent fluidity of water is maintained even in molecular scale gap between contacting surfaces, which is, of course, the major origin of low friction in boundary lubrication. However, this high fluidity may result in the easily squeezed out of water from the gap, which leads to surface damage. Selecting suitable chemicals as lubricant additives is one of the solutions for this problem; the impact of using water-soluble polymers as additives for water lubrication was investigated. We found that some silicone-type amphiphilic polymer formed an adsorbed layer on surface and exhibited excellent tribological performance mainly due to the easy slippage of hydrated water on polymer layer surface.

Our group has successfully fabricated pyramidal structures with Si{111} clean faceted surfaces (edge width W 16 μm) on Si(001) substrate by combining Si substrate processing technology and ultra-high vacuum surface technology, and performed Fe deposition (film thickness ΘFe 30 nm). The magnetization field (M-H) curve of the pyramid-shaped Fe nanofilm controlled with atomic precision was measured by vibrating sample magnetometer, and the characteristic of the M-H curve (bending point due to stable magnetic vortex formation) predicted by LLG was observed [3]. In the present study, in order to further understand the magnetic behavior of three-dimensional magnetic nanofilms, we have investigated 1) the thickness dependence of Fe film and 2) the aspect ratio dependence of the pyramidal structure with different length (L) and fixed-width (W), that is, the facet line structure. In this talk, we will report the details.

Topological insulators (TI) are insulating in the bulk but have metallic spin-polarized edge (surface) states. This surface state has a linear type dispersion called the Dirac cone. By inducing magnetism in TI, a Dirac cone gap opens and the Quantum anomalous Hall effect (QAHE), in which the Hall resistance is quantized at zero field, can occur. In the magnetic topological insulator heterostructure, a gap opens at the surface Dirac cone, but a gapless state remains at the interface with the substrate, which hinders the appearance of the QAHE. Therefore, it is necessary to develop the heterostructure into a sandwich structure and to create a ferromagnetic layer on the bottom surface as well. However, the interaction between the two magnetic layers is still unknown. In this study, we investigated the electronic state and magnetization properties of the sandwich structure by Angle-resolved Photoemission Spectroscopy (ARPES) and X-ray Magnetic Circular Dichroism (XMCD) measurements.

We grew 1 unit layer (u.l.) of a Ce-Pt intermetallic compound on Pt(111) and observed the structure and the electronic states using scanning tunneling microscopy/spectroscopy. Atomically resolved observation revealed the formation of an ordered (2×2)-CePt₆/Pt(111) with a pure Pt atomic layer at the surface. By measuring quasiparticle interference at 5 K, we found that the surface state on Pt(111) above Fermi energy shifts downward on the topmost Pt layer of the 1 u.l. CePt₆, indicating charge transfer from the underneath CePt₂ layer. The observed zero-bias anomaly in the tunneling spectra suggests a coherent Kondo state.

The charge density wave (CDW) state of 2H-NbSe₂ has been studied using a low-temperature scanning tunneling microscope (STM). The CDW domain structure is determined from atomic resolution STM images by means of Fourier-transform or convolution based displacement analysis.

Nodal line semimetals, whose valence and conduction bands cross on a line in the Brillouin zone, have attracted a lot of attention as a new class of topological materials. Recently it has been reported that NaAlSi is belong to nodal line semimetals and it shows superconducting transition at 7K, which is relatively high temperature. We will present the electronic properties of NaAlSi measured by low temperature scanning tunneling microscopy.

We characterized the magnetic-field-driven superconductor-insulator transition (SIT) of Pb mono-atomic-layer thin films formed on Si(111) substrates with various step density by electrical conductance measurements and scanning tunneling microscopy / spectroscopy (STM/S). From the conductance measurements, we found that the critical temperature is lowered but the orbital critical magnetic field is enhanced with the step density. In addition, the behavior of the anomalous metallic state, which is often observed on highly crystalline 2D superconductors, depends on the step density. Interestingly, in the case of the sample with large step density, the superconducting gap still remains under magnetic fields above the orbital critical field. We expect that the remaining gap implies the presence of Bose insulating phase, in which the Cooper pairs are still remaining but localized.

We have been investigated superconductivity in the monolayer FeSe on the SrTiO₃ substrate by means of in situ four-point probe electrical transport measurements. In this study, we changed the substrate from undoped to Nb-doped SrTiO₃, which is expected to induce a superconducting transition to the FeSe at a higher temperature. Due to the parallel conductivity through the Nb-doped SrTiO₃, the superconducting transition is likely to appear as a small resistance change on the order of mΩ. Accordingly, we improved the accuracy of temperature control and resistance measurements. We demonstrate the improvement by showing the superconductivity in Nb thin films, followed by the results on the temperature-dependent sheet resistance and the I-V characteristics of the monolayer FeSe on the Nb-doped SrTiO₃.

Surface metal superstructures on semiconductors have different electronic states from those in the bulk, and superconducting transitions have been confirmed. Such a low-dimensional electronic state can be very sensitive to surfaces and interfaces, and it is possible to change their physical properties by depositing other materials on the surface and taking advantage of proximity effects such as charge transfer and exchange interactions. In this study, we deposited PTCDA and ZnPc molecules on the atomic layer superconductor Si(111)-(√7×√3)-In, and investigated the variation in the superconducting transition temperature (T_c) as a function of molecule coverage. T_c was obtained through electron transport measurements under ultrahigh vacuum. T_c were found to decrease for PTCDA and increased for ZnPc. Scanning Tunneling microscopy results show that the adsorption structure affects the change in T_c.

The diradical state is one of the important electronic states for theoretically invesitgations on open-shell molecules (e.g. enzyme, single-molecule magnets, and etc.). On the other hand, there is no simple scheme to estimate the features of the diradical state from the results of the DFT/plane-wave, which is a general ab-initio calculation method for solid surfaces; hence, data-driven surface science and surface interaction analysis for the systems are suppressed. In this presentation, we propose a simple method to analyze diradical characters based on charge density, and invesitgate the effects of surface interactions on the diradical states.

Recent studies have revealed that Amontons' law of friction systematically breaks down for viscoelastic objects due to precursor slips occurring before the onset of bulk sliding in 2D system. However, it is not clear whether this result is applicable to more realistic 3D systems. In this study, we numerically investigate the slip motion of a 3D viscoelastic object on a solid substrate using a finite element method to resolve the problem mentioned above. The result indicates that the behavior of precursor slips and the macroscopic static friction coefficient depends on the pressure and the size of the object. Our theoretical analysis of a 1D effective model clarifies that the bulk sliding results from the instability associated with the competition between a velocity-weakening local friction and the bulk viscosity. The instability explains the dependence of the macroscopic static friction coefficient on the pressure and the size of the object.

The surface of ice is known as the place where various phenomena occur. However, the detailed surface structure is still unknown. In this study, we used atomic force microscopy to observe the growth and surface structure of ice on a KCl(001) substrate. As a result, when the amount of water exposure was small, a novel periodic structure, which seems to be the interface structure, were observed. On the other hand, when the amount of water was increased, the substrate was covered with uniform crystalline ice, and the surface showed the same structure as that grown on the metal substrates.

Understanding and predicting the property of water on several metal surfaces can be a guide for improving the performance of electrochemical devices. A lot of previous studies has been extensively conducted for water molecules on metal surfaces. We aim to understand the behavior of the water orientation structure on metal surfaces by employing first-principles calculations. In the presentation, the structures of monolayer ice on the surface of Pt (111) are investigated, and the most stable structure is compared and discussed for consistency with the experimental results.

In the formation of molecules which have halogen atoms, hydrogen and halogen bonds are important to determine the molecular crystal and films. In this study, we carried out STM measurement of adsorbed 1,3,5-tris(4-bromophenyl)benzene molecules on Si(111) (√3×√3)-Ag and multilayer Ag films. From the measurement, molecular films with various structures are obtained. We discuss the formation mechanisms of the films.

Organic molecules with large dipole moment were deposited on noble metal surfaces and examined to form low-dimensinal structures by means of scanning tunneling microscopy in ultrahigh vacuum.

We examined to form a two-dimensional molecular lattice film on noble metal surfaces in ultrahigh vacuum using precursol molcecules via Ullmann coupling. We used Cu(111) and Au(001) substrates. Sample surface morphology was measured by means of scanning tunneling microscope and low energy electron diffraction. Sample electronic structures were investigated by scanning tunneling spectroscopy and ultraviolet photoelectron spectroscopy. We will report in detail.

Host-guest system has been used as a molecualr machine, which shape can be changed by external stimuli in solution and bulk crystals. Here we studied on-surface construction of host-guest molecular system grown on an atomically flat and clean noble metal surface using low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) as well as ultraviolet photoemission spectroscopy (UPS) in ultrahigh vacuum.

Alloy cluster is expected to have unique properties compared to bulk crystal and nanoparticles, but experimental method for alloy cluster is now limited. In this study, direct observation of alloy cluster was conducted by using scanning transmission electron microscopy (STEM) which has atomic resolution. Finally, we succeeded to establish an analytical method for auto-identification of different period metal elements. The present results suggest that direct observation method by STEM is useful for new experimental method for alloy cluster.

Muon, which has a spin 1/2, finite life time to eject positron in the spin direction and about 1/9 weight of the proton, can be used as a probe to specify the behavior and local structure of hydrogen inside materials. The methodology is called as muon spin rotation/relaxation (μSR) spectroscopy. Recently accelerator based strong pulse muon facilities have been developed and has opened the new feasibility for μSR measurements. TiO₂ is the most widely used material as high efficiency photocatalysis. One of the crucial and unrevealed issues are properties of defects, e.g. oxygen vacancies, hydrogen. Recently hydrogen dissolved in TiO₂ during preparation process forms impurity states in the band gap to change electron excitation process and electron conductivity. We applied μSR measurement on the TiO₂ single crystal in order to understand the behavior and electronic properties of both defects and impurities. In this contribution we will show the muon interaction with oxygen vacancy of TiO₂ by zero-field, longitudinal and transverse external field μSR spectra. Those results show stable sites of muon (hydrogen) and electron distribution in the reduced TiO₂.

Analyses of interface structures between electrodes and solid electrolytes as well as Li-ion distribution at the interfaces are significant to understand the operation mechanism of novel memory devices using the Au/Li₃PO₄/Li stacked structures. In this study, we constructed an interatomic potential of Au/Li₃PO₄ interface systems using a neural network, based on density functional theory calculations. We will report the results of Li-defect behavior near the interface obtained by the constructed potential.

Electronic structures derived from a local defect in graphene play important roles in various engineering fields. We used scanning tunneling microscopy to observe a monolayer nanographene sheet, which was cleaved from a graphite surface. We focused on a unique rectangular-like lattice and investigated its characteristics in detail. Moreover, the electronic structures of graphene nanoribbons were calculated based on first principles, which unveiled the origin of the rectangular-like lattice.

Monolayer iron selenide (ML FeSe) on strontium titanate (STO) is a superconductor with T_c over 60 K, in which the STO substrate plays an important role in the high T_c. To figure out the local effect of the STO surface reconstruction on ML FeSe, we use low temperature (5 K) scanning tunneling microscopy/spectroscopy (STM/STS) to measure the correlation between the surface structure and the electronic state as well as the superconductivity of ML FeSe/STO -√13×√13. In the atomically-resolved STM images, we observed 1×1-only area, periodically arranged 'z'-like patterns, and dumbbell-like defects. The STS spectra have been simultaneously measured in the corresponding regions on the surface and the details will be shown in the presentation.

Boron contained two-dimensional materials are known to exhibit various stable structures (polymorphisms). For this reason, it can be viewed as difficult to handle for application, but it can also be viewed as an attractive material with the potential for many different physical characteristics. Of these, we have created a hydrogen boride sheet, which is a type of two-dimensional sheet of hydrogenated boron, and a boron sulfide sheet, and have investigated their properties. In this talk, we will report on our achievements and recent developments.

In TOF-SIMS measurements, it is difficult to detect the intact ions of macromolecules because the detection limit of that tends to be lower than that of small molecules. Matrix enhanced SIMS is one of the sensitivity enhancement techniques of organic molecules. In this study, we investigated the sensitivity enhancement of phospholipids using aliphatic carbonic acid matrix in TOF-SIMS.

In order to control the function of solution products such as daily necessities, it is important to clarify the relationship between composition and structure. Therefore, we have considered a Cryo-TOF-SIMS/SEM method combined Cryo-TOF-SIMS and Cryo-SEM to analyze the composition and structure of solutions. As a result of analysis of a model fabric softener, spherical structures were observed and active ingredients were distributed at specific positions in the structures. The storage stability of two model softeners was discussed from the results of Cryo-TOF-SIMS/SEM. A new point of view for the formulation study of softeners was obtained through this research.

Three-dimensional atomic force microscopy is a technique that has a capable of visualizing three-dimensional fluctuating molecular structures at the solid-liquid interface of a sample. In the biological and medical fields, this 3D-AFM is expected to be used to measure the 3D internal structure of three-dimensional biological samples such as cells and chromosomes. In this study, we fabricated sharp probes made of carbon nanotubes (CNTs) using an electron microscope and performed internal measurements of chromosomes. As a result, the CNT tip penetrated into the chromosome, and it is highly likely that the force distribution reflecting the internal information was obtained. Furthermore, this method will be expected to apply to a wide variety of biological samples, not only chromosomes.

We applied c-AFM to all-solid-state batteries to observe local electrochemical reaction. Battery samples were prepared using Li(Ni_1/3Mn_1/3Co_1/3)O₂ as the cathode active material and Li₂S-P₂S₅ (LPS) as the solid electrolyte, and the cross-section of the cathode was observed by c-AFM. The result showed that charging current was observed at NMC/LPS interfaces and also grain boundaries inside MNC particles.

To improve the performance of catalysts and batteries, it is very important to visualize the surface reactivity with the structure on a micro/nanoscale to understand the crystal orientation and grain boundary-dependent reactivity. Therefore, we have developed scanning electrochemical cell microscopy that uses a nanopipette as a probe to locally form an electrochemical cell and scan the nanopipette on the sample surface to visualize the reactivity of the sample surface. Using SECCM, we characterized the hydrogen evolution reaction of nanosheet material and the charge/discharge property of the lithium-ion secondary battery.

Recent progress in biological applications of cold atmospheric pressure plasma shows that the biological effects are mainly due to oxidative reactions induced by reactive species produced by exposure to the plasma. It is generally accepted that oxidative stress eventually causes damage to nucleic acids; therefore, nucleic acids are an essential biomolecular target for investigating the effects of plasma exposure. We have developed novel methodologies to assess the damage to nucleic acids and combined them with synthetic cell models. We also reported that plasma irradiation induces chemical modification of DNA bases as well as strand breaks. Furthermore, up-regulation of the DNA repair process in the plasma-irradiated cells was also observed.

In order to evaluate the performance of the decomposition rate of gas-liquid interface plasma for the decomposition of polymers, we decomposed proteins known as persistent polymers. We have compared our data with those by the reported method of microbubble-assisted plasma in water. In the case of microbubble-assisted plasma in water, it took 60 minutes for reducing 0.1 mg/mL down to 0.01 mg/L or less, whereas in the case of our method, it took only 3 minutes.

In order to solve these problems, we focused on the magnetic field lens using a permanent magnet that generates a small and strong magnetic field. In this study, we focused on a magnetic field lens using a permanent magnet that emits a strong magnetic field in a small size to solve these problems, and fabricated a magnetic field lens by analyzing the magnetic field using the finite element method and designing the shape of steel.

Most of the semiconducting properties of EuO, a ferromagnetic semiconductor, are still unknown, and there are no reports of electrochemical measurements. In this study, Nb-doped SrTiO₃ (STO) single crystal substrate with electrical conductivity is employed. However, the thermal diffusion of oxygen from the STO substrate interface into the film during substrate heating prevents the high quality of EuO thin film. In this talk, we will discuss the effects of introducing SrO buffer layer and vacuum post-annealing on the fabrication of EuO thin films on STO substrates.