The NV center: defect center in a diamond can be attached at the apex of an atomic force microscope (AFM) enabling nanoscale quantum sensing and imaging. We introduce NV probe fabrication using laser cutting and focused ion beam fabrication. The magnetic tape sample, where periodic magnetic domain structures were formed to demonstrate stray magnetic field sensing and imaging via optically detected magnetic resonance mapping synchronized with AFM topographic imaging.

Surface modification is an effective and economical surface treatment technique for many materials and of growing interests in biomedical engineering. This article concentrates upon the current status of these techniques, new applications, and achievements pertaining to biomedical materials research.

Field electron emission from nanocarbon materials such as carbon nanotubes and graphene and related studies are reviewed.

Thanking for the Sakaki Achievement Award, my activities of R&D of EDX systems and international standardizaion will be reported.

Surface micro- and nanobubbles were formed by electron irradiation under a low magnification observation condition in a conventional scanning electron microscope. The irradiation dose rate used in this study was 5—7 orders of magnitude smaller than those in previous TEM studies. The cross-sectional shape of the bubbles was hemispherical regardless of size, and no pancake-shaped bubbles reported in previous AFM studies were observed. The lifetime of the bubble was at least 3 days.

By introducing gas into a near-ambient pressure hard X-ray photoelectron spectroscopy (NAP-HAXPES) apparatus, the charging effect of insulator samples such as a glass plate could be almost completely eliminated. Furthermore, it was clarified that the gas pressure required for charge elimination strongly depends on the distance between the sample and the front cone of the HiPP-2 analyzer.

We have measured the E/n dependence of SIMS spectra of nitrobenzylpyridinium salts (NBPs) using a size-selected argon (Ar) cluster TOF-SIMS apparatus which can select the size (n) of the cluster ion. The E/n dependency of fragment ion intensity may be due to the reaction path of fragment formation. We also examined a method to classify the fragment ions based on the correlation coefficient of the E/n-dependent curves.

The higher resolution images of the hydrogen distribution on the surface of thin stainless steel measured by electron stimulated desorption (ESD), the scanning electron microscope image, and the electron backscatter diffraction images were fused by imregister of Matlab (Mathworks). The fused data set was analyzed by the principal component analysis (PCA) and autoencoder (AE). PCA results of higher resolution data analysis showed consistent findings with the previous studies regarding the relation of crystal structure and hydrogen distribution in steel, and AE indicated more detailed information on the structures.

Vibrational states and location of H atoms near two dimensional surfaces are not well known. In the present study, we successfully performed inelastic neutron scattering and obtained vibrational spectra of H in 8-nm-thick Pd films. While the vibrational spectra are similar to those in nanoparticles at low energy region, they are similar to those in bulks at high energy region. It is revealed that the vibrational states of H near flat surfaces are unique and have both characteristics of bulk and nanoparticle.

Plasmon, a gold nanoparticle, has been attracting attention in recent years. We have applied plasmons of gold nanoparticles to reduce damage to the plasma-irradiated surface due to ionic impact and to utilize it for the formation of high-quality ultrathin films. This time, we investigated the effect of silicon on radical oxidation at room temperature.

To improve the quality of films while taking advantage of low-temperature film deposition, we have proposed a unique sputtering device capable of convergent irradiation of high-density plasmas to the liquid metal target surface using a convergent magnetic field generated by an external coil and a permanent magnet. This convergent magnetic field suppresses the ion damage caused by high-energy ions in plasmas and the temperature rise of the substrate caused by secondary electrons from the target surface. In this presentation, we present the temperature dependence of the low-temperature epitaxial-like growth of GaN thin films obtained by using our sputtering device.

Al₂O₃ thin films, as an attractive candidate for insulated gate for GaN-based metal-insulator-semiconductor (MIS) structures, were synthesized by cost-effective mist chemical vapor deposition (CVD) technique. The properties of deposited Al₂O₃ thin films are comparable to those reported from high-quality amorphous Al₂O₃ thin films deposited by atomic layer deposition method. In addition, we fabricated AlGaN/GaN MIS diodes using Al₂O₃ gate insulator mist-CVD technique. Capacitance–voltage investigations indicated high quality of the resulting mist-Al₂O₃/AlGaN interfaces.

VO₂, which is a strongly correlated metal dioxide, has the potential to be fabricated as a thermal trigger because of the characteristics of metal-insulator transition (MIT) around the room temperature. In this research, in order to clarify the MIT behavior affected by the planarly confinement effect, the MIT process of VO₂ micron structures was systematically studied, and the phenomenon of the phase transition temperature change depending on the confined VO₂ structures size was found. As the sample size increases from 2 to 10 μm, the phase transition temperature shows a totally upward trend from 268—277 to 276—285 K. This result implies that the transition temperature was converted by virtues of the spatial confinement.

Defects which have isolated energy levels in bandgap of wide bandgap semiconductors act as single photon source, quantum bit (qubit) and quantum sensor. Since such defects are expected to be applied to quantum technologies, the studies of such defects are intensively carried out all over the world. Here, I would focus on defects which act as single photon source in silicon carbide (SiC), such as negatively charged Si vacancy (V_Si), neutral divacancy (V_SiV_C), carbon antisite-silicon vacancy pair (C_SiV_C), negatively charged nitrogen-vacancy pair (N_CV_Si) and oxygen-related defects near surface (its structure has not yet been identified). In the presentation, the optical and spin characteristics of such defects will be introduced. Also, the creation methodologies for such defects using particle irradiation and subsequent treatments, and oxidation will be shown. Then finally, future applications of such defects toward quantum technologies will be discussed.

The chemical reactions induced by localized surface plasmon (LSP) has attracted great attention in recent years. Although the reactions have been extensively studied, the reaction mechanisms are still controversial. This is mainly because the investigation of the local chemical reactions induced by LSP is difficult by using conventional macroscopic methods. To obtain mechanistic insights, nanoscale observations and investigations are important. In our research, a scanning tunneling microscope (STM) combined with optical excitation have been used to investigate single-molecule reactions induced by LSP.

In recent years, the progress of miniaturization of electronic devices stimulates a growing interest in low dimensional materials. Among them, silicene, the allotrope of silicon equivalent of graphene, has attracted increasing attention owing to its superior electronic properties. Silicene has a honeycomb structure similar to graphene. The band structure of silicene, which forms ‘Dirac cone’ at the symmetric point K in the reciprocal space, indicates that the charge carriers in silicene sheets behave like massless Dirac fermions. In this presentation, the high-resolution AFM imaging of silicene on Ag(111) and investigation of Si nanoribbons on Ag(111) by STM and AFM will be talked about.

In this work, we developed a novel nano-spectroscopy technique, entitled terahertz-field-driven scanning tunneling luminescence (THz-STL) spectroscopy, based on a scanning tunneling microscope (STM). THz-STL spectroscopy combines two cutting-edge STM techniques, THz-STM and STL spectroscopy, and enables to investigate atomic-scale energy dissipations triggered by a THz single-cycle pulse. We introduced single-cycle THz pulses into an STM junction (Au tip and Ag(111)) and measured visible photons generated by THz-field-driven electrons. By utilizing this technique, we detected the radiative decay of a localized plasmon excited by THz-field-driven electrons and clarified mechanistic differences in plasmon excitation between field- and DC-driven electrons.

Photo-induced force microscopy (PiFM) is based on atomic force microscopy (AFM) and is capable of observing optical properties of sample surfaces with nanoscale resolution. In this study, we used Photo-induced force microscopy to observe the optical properties of pentacene thin films at the nanoscale. As a result, we found that the photo-induced force of the second layer of pentacene film on the silver substrate is larger than that of the first layer.

Nitrogen-doped graphene is one of the platinum alternative catalysts for oxygen reduction reaction for polymer electrolyte fuel cells. We have clarified that the pyridine-type nitrogen at the active site undergoes thermal oxygen adsorption and reduction reaction at the same time, and this reaction tends to proceed in a hydrophobic environment. In this study, we synthesized a nitrogen-doped graphene catalyst with enhanced macroscopic hydrophobicity, evaluated the microscopic hydrophobicity near the active point by XPS and acid-base titration, and compared it with the activity.

N-doped carbon is one of the oxygen reduction reaction (ORR) catalysts as a platinum alternative catalyst for polymer electrolyte fuel cells. And we have shown that pyridinic nitrogen forms active points. However, the decrease in activity in acid is a problem for practical use. And the reaction inhibition mechanism has not yet been clarified. In this study, the behavior of pyridinic nitrogen in an acid-base electrolyte solution was evaluated by electrochemical measurement and surface chemistry.

Graphene has been one of the most attractive materials since its discovery, due to the unique structural properties and usefulness in a broad class of applications. Doping graphene with foreign elements has also been investigated to tailor its electronic properties to provide new possibilities for more application. Nitrogen (N) is one of the most frequently studied dopings, in particular, for improving the electrocatalytic activity of oxygen reduction reaction (ORR) in the fuel cell application. It was reported that the intrinsic physico-chemical properties and catalytic reactivity Of N-doping graphene are governed by the N-concentration and its local structures (e.g., graphitic and pyridinic-N). However, the role of the N-doping of graphene in catalytic reaction has not been fully understood. As a first step to fully understand the origin of the electrochemical ORR, it is essential to understand its interaction with water, as it plays a central role.

Two-dimensional (2D) materials that can be obtained by exfoliation of layered crystals are very sensitive to surface phenomena owing to their ultimate thinness. Their ultrathin body enables us to control the entire body by means of a field-effect-transistor (FET) configuration because the gate electric field penetrates to the top-most surface. Thus, it is expected that surface phenomena are controllable by means of FETs with a channel of 2D materials. In this talk, among various gate-controlled surface phenomena, gate-controlled chemical reactions will be discussed based on chemical modification of an archetypal 2D material, graphene.

To understand surface processes, it is useful to observe in situ the surfaces directly where the surface processes proceed. Based on this viewpoint, we have been working on in situ observations of the surfaces by means of core-level spectroscopies, with developing new relating techniques. In particular, molecular self-assembling and catalytic reactions at surfaces have been studied with keen interest. New interesting aspects of these processes have been uncovered via in situ observations. Here a few examples for such aspects will be introduced.

Molybdenum carbide, which is expected to be as a low cost catalyst similar to platinum, is formed by high temperature reactions of molybdenum and carbon at higher than 2000 K. In this study, the structural dynamics of the high temperature formation using laser heating was in situ observed by transmission electron microscopy.

Reduced molybdenum oxide (H_xMoO_3-y) obtained through hydrogen reduction of MoO₃ has two distinctive properties. One is abundant oxygen vacancies and another is strong absorption of visible light. The application of these features to the catalytic reactions is being investigated. In this study, the structures of the catalyst under the reaction conditions were investigated by using in-situ XAFS and in-situ UV-vis measurements. The activity of the reverse water gas shift reaction was enhanced depending on the amount of oxygen vacancies, and in-situ XAFS measurement results suggest that the reaction proceeds via a reversible redox behavior of oxygen vacancies. In addition, the activity of the reaction under visible light irradiation increased more than two-fold, and the in-situ UV-vis measurement results suggest that the increase in the visible light region is due to the plasmon-originated light absorption.

Hydrogen spillover is a surface phenomenon that occurs on noble-metal-deposited reducible support. This process is initiated by the dissociation of hydrogen molecules, and then the hydrogen atom migrates from the metal particle to the surface of the support. A reduction assisted by the hydrogen spillover process can reduce metal cation and form an oxygen vacancy. In this work, reduced titanium dioxide with nanorod shape (TiO_2−x) was developed, via the reduction treatment assisted by hydrogen spillover under mild reduction conditions. In the ESR analysis, the signals attributed to Ti³⁺ and oxygen vacancy were observed after the reduction treatment, and their amount increased with an increase of the reduction temperature. The photocatalytic activity over the obtained titanium dioxide nanorod photocatalyst reduced at the lower temperature exhibited the highest activity under visible light irradiation. These results suggested that Ti³⁺ induced via the reduction assisted by hydrogen spillover improved photogenerated electron conductivity which led to the enhancement of the photocatalytic activity.

Polymerization of amino acids through a dry-wet cycle on mineral surfaces is one of the processes in the chemical evolution theory from amino acids to complex protein structures. The dry-wet cycle can allow intermittent and repetitive supply of water-soluble organic molecules and their dehydration condensation. Focusing on amino acids that are essential to living organisms, the abiotic polymerization process of amino acids by dehydration reaction is essential for complex peptide formation on the prebiotic Earth. In particular, the production of hetero-dipeptides from heterologous amino acids is the key to the birth of a wide variety of peptides composed of amino acids. Titanium oxide, which is abundant on the earth, is known as a promising mineral for polymerization of amino acids. Here, in this study, we synthesized hetero-dipeptides on titanium dioxide by the dry-wet cycle.

MoS₂ is a layered material that has attracted attention as a new device material that can replace existing materials such as semiconductors and electrodes for ion batteries. In recent studies, lattice relaxation, which is a phenomenon unique to layered materials, has been reported to change the layer structure by intercalation. We have measured Na-intercalated single crystal MoS₂ and attempted to analyze the 3D atomic arrangement of Na. In this presentation, we will report the layer structure change and the existence site of Na by comparing with the calculation.

In X-ray photoelectron spectroscopy (XPS), even if the same single-phase compound sample is measured, the shape of the observed spectrum differs depending on the measurement device and experimental conditions. Therefore, in identifying unknown samples by XPS, the method of referring to the observed spectra of single-phase compounds in the XPS database obtained by different instruments depends on the operator. In this study, we developed a method for estimating the common peak structure from a large number of observation spectra that are fluctuated by measurement, eliminating the fluctuation.

RHEED (reflection high-energy electron diffraction) is a widely used method for in-situ surface structural analysis of thin films. Since it is difficult to interpret the entire patterns quantitatively, researchers often use limited information such as the intensity oscillation at a given diffraction spot in film thickness estimation. Here, we adopted machine learning techniques for feature extraction from the entire RHEED patterns. We performed peak fitting analysis of the luminance histogram obtained from the time-series image datasets of RHEED patterns of Si surface superstructures during Indium deposition using EM algorithm. One peak component corresponds to the background, and the other corresponds to the diffraction spots. By tracking the change in the dispersion value of the peak, the optimal time for preparing each surface superstructure could be estimated automatically. Our method is expected for the application in data-driven material synthesis.

To improve the performance of three-dimensional MEMS devices, it is important to control the sidewall surface and facet surface of the three-dimensional structure, which are the boundary region with the external world and carrier transport region, with atomic precision. We have developed a multi-axis RHEED system to generate three-dimensional inverse spatial maps from multiple RHEED patterns with different electron beam incident azimuth angles (φ). Now, we have successfully measured the faceted surface of 3D-Si sample by improving the measurement equipment and software. In this talk, we will report the details.

The original methodology that enable to produce and observe atomic orderings and arrangements of “surfaces with arbitrary directions” on three-dimensionally (3D) figured structures. The atomically-ordered 3D nanofabrication technique, where the material stacking direction is switched from the general out-of-plane to in-plane direction, and realized the formation ultra-thin epitaxial films in 3D space. The realization of 3D surfaces is committed to fostering a new study field in surface science, that is diverse and inclusive.

Titanium dioxide (TiO₂) photocatalyst is one of the semiconductors that shows the effect of water/air purification, deodrant, or antibacterial/sterilization by UV light irradiation. For visible light sensitivity, we synthesized Cu-doped TiO₂ nanoparticles via liquid phase deposition method, which is known as an approach with low energy and low impact to environment. The products were carefully characterized and applied for photocatalysis. The obtained nanoparticles are found to be TiO₂ with anatase phase, while those with Cu-doping showed visible light absorption. The light absorption edge is confirmed to shift to 550 nm after optimizing the concentration of Cu.

In recent years, the resistive switch effect, which controls the polymerization and dissociation of fullerenes, has been reported in voltage-applied experiments using a scanning tunneling microscope, and its application to memory devices has been suggested. In this study, we fabricated a planar two-terminal structure using C₆₀ pyrrolidine-trisacid (CPTA) thin film and electron beam lithography to design the device structure, and investigated its dependence on the electron irradiation region. In the CPTA thin film device, the change of the current in the electron beam irradiation region was confirmed.

Considering the edge-edge and van der Waals (vdW) interactions, we studied the structural stability and electronic properties of zigzag AA-stacked bilayer SiC nanoribbon (ZSiCNR). The hetero-AA stacked SiCNR is much more stable than the homo-stacked one, which is mainly attributed to the formation of sp³ bonds at both Si-C edges. The electronic properties are strongly dependent on the stacking patterns: the homo-AA stacked ZSiCNR is a metal, whereas the hetro-AA sacked one becomes semiconducting.

We have found nonlinearity in the current-voltage characteristics by resonant tunneling of a gold electrode modified with a self-assembled monolayer (SAM) and N719 and cross-linked with gold particles. However, the details of the resonance tunneling mechanism have not been elucidated. In this study, the charge transfer between N719 and Au via SAM was observed by frequency modulation mode atomic force microscopy (FM-AFM) in order to elucidate the mechanism in detail.

In the field of organic electronics, many studies have been reported on self-assembled membranes (SAMs) composed of a single type of molecule. Recently, however, much attention has been focused on how charges are transferred in molecular films composed of multiple components. In this study, we focused on the switch mechanism in a multi-component molecular membrane. In this study, we focused on molecules with electron-withdrawing groups in their alkyl chains.

The nitric oxide (NO) molecule was placed on copper nitride and the bent NO and upright NO were found on the monoatomic line. we successfully used a metal probe and switched the bent NO to the upright NO using the attractive force.

We have succeeded for the first time in observing the high-density phase of a monolayer of oxygen molecules on Ag(111) in real space by atomic force microscopy. It was difficult to observe nondestructively by scanning tunneling microscopy.The local observation revealed that the phase has a domain structure and lattice distortion, which had not been reported previously. Magnetic phase transitions with lattice deformation have been reported on graphite substrates, so the lattice distortion is expected to be related to the spin of oxygen molecules.

In this lecture, the presenter describes his research on transport phenomena in nanostructures by theoretical calculations with high prediction accuracy. Topics in the lecture include development and application of methods to analyze the field electron emission from surface nanostructures and transport properties between two electrodes or among multiple electrodes, study on memory devices where switching occurs by ion migration in the insulating layer between electrodes, and development and applications of machine-learning potentials to analyze ion migration behaviors and thermal transport.

In this study, we fabricated a cross-linked single-molecule junction between two Au electrodes and four molecules with different bonding types, and measured the electrical conductivity. By combining the results with the calculation of the potential energy of the junction, the relationship between the binding strength between the metal and the single molecule and the electrical conductivity of the single molecule was clarified. In order to obtain higher structural and electrical stability at the metal-molecule interface, we found that it is necessary to design the molecule including not only the anchor group but also its adsorption site.

As a hydrophobic material, graphene had long been thought to be impervious to the aggregation of water molecules. However, recent studies have shown that water molecules aggregate in layers on the surface of graphene due to van der Waals forces under atmospheric pressure. In this study, we analyzed the rotational motion of the water layers on the graphene interface using molecular dynamics simulations. The results indicate that the rotational motion is more random as it approaches from the graphene surface to the bulk region.

As a method for reducing the outgassing from the inside of the vacuum material, high-temperature heat treatment under a high vacuum called vacuum firing has been known. The conditions for vacuum firing are 900°C for 2 hours for stainless steel at CERN and 850°C for 10 hours for titanium at the J-PARC, and so on. The reduction of hydrogen concentration in the material by vacuum firing has been reported by comparison with the non-vacuum firing material. On the other hand, there is no clear data, that shows the lower outgassing rate of the vacuum-fired material than that of non-vacuum-fired one. In this conference, we report the clear difference between them, which has been observed in the build-up test.

0.2% Be-Cu has characteristics such as 13 times higher heat conduction than SUS, low heat radiation of 1/7 or less, and low degassing, and is applied to ultra-high vacuum pressure gauges. The minimal fab system, which is a high-mix low-volume production scheme for semiconductors, uses a small vacuum vessel, but the impact on the process of vacuum vessel surface quality is inevitably large. This time, a container equivalent to the vacuum container of the minimal device made of SUS was made with 0.2% Be-Cu, and its superiority as a vacuum process container was confirmed.

Optimized mechanical grinding (OMG) was developed as a low outgassing surface finishing for aluminum alloys (A5052). Surface morphology and depth profile for aluminum alloys with four types of surface finishes, i.e. conventional mechanical grinding (MG), mechanical grinding with optimized process (OMG), and combination of each grinding and chemical polishing (MG+CP and OMG+CP), were investigated using atomic force microscopy and X-ray photoelectron spectroscopy. The depth profile of the MG showed a gradual increase in aluminum (Al) concentration and a gradual decrease in oxygen (O) concentration. But in the depth profiles of MG+CP, OMG, and OMG+CP, the precipitous increasing of the Al concentration and the precipitous decreasing of the O concentration appeared. Also, approximately 5% of carbon (C) remained to a depth of 100 nm in the MG. On the other hand, C concentration of MG+CP, OMG, and OMG+CP was 0% at depth more than 10 nm. Therefore, the surface layer of the OMG and chemical polishing aluminum alloy surface finished samples were found to have a thin oxide layer of approximately 10 nm without processing alteration, and low outgassing rate.

Non-evaporable getter (NEG) denotes a group of materials that can be activated by heating under ultrahigh vacuum (UHV) and can pump residual gases at room temperature. Recently, single metallic Zr or Ti thin films were reported to work as NEG with activation temperature of about 200°C. In this study, a zirconium thin film deposited onto a sawtooth shaped substrate by sputtering method was baked at 150—200°C for 12—24 hours under UHV. Although pumping speed for H₂ was below the detection limit, the pressure in the chamber after baking reached the range of 10⁻⁸ Pa at room temperature, suggesting that the Zr thin film pumps H₂O and CO. We will also report the pumping properties of a titanium film deposited by sputtering method in the vacuum environment of 10⁻⁷ Pa.

We have studied the electronic structure and electrical conduction of ultrathin Bi₂Te₃ films grown on CaF₂(111)/Si(111) by molecular beam epitaxy. Angle-resolved photoelectron spectroscopy (ARPES) showed that the electronic structure of the films near the Fermi level consists of a surface band and a conduction band. Sheet electrical conductivity of the films was measured by a home-built UHV-compatible four-point probe. Residual conductivity σ₀ measured at 10 K showed a rapid increase above three quintuple layer (QL). ARPES and low-energy electron diffraction (LEED) results indicate that the thickness dependence in σ₀ is mainly attributed to the improvement of crystal quality of the films.

Unconventional superconductivity can be introduced in graphene by fine-tuning the van Hove singularity (VHS) position near the Fermi level. In this study, we examined the binding energy of VHS upon lithium intercalation into graphene with different thicknesses. From bilayer to multilayer, VHS shifted from the vicinity of the Fermi level to the occupied state by 60 meV. We performed first-principle calculations without and with the substrate. The former showed that interlayer interaction moves VHS more than experiments. The latter indicated that hybridization with the surface state of the substrate alters the dispersion of the Dirac bands, which can pin the VHS near the Fermi level.

Dynamical behavior of carriers in graphene has attracted academic interests to investigate temporal evolutions of the massless Dirac Fermions and also technical needs to develop the next-generation optoelectronic devices. The comprehensive understanding has been conducted by direct observations of the electronic states by time- and angle-resolved photoemission spectroscopy (TARPES). TARPES measurements on the epitaxial quasi-crystalline bilayer graphene observed the transient voltage between the two layers that were not expected theoretically. The experimental reasoning has required contributions from the substrate or the interface but the detailed scenario has remained unknown. In the present research, we performed TARPES measurements on various systems of single and bilayer graphene on the Si-face SiC substrates to extensively study the carrier dynamics. The quantitative discussion was made with the structural parameters, interlayer distance, determined by positron diffraction (PD) experiments. The concerting usages of TARPES and PD quantitatively revealed the transport mechanism that was induced by the optical pumping.

We have studied the evolution of atomic and electronic structure of the double-layer indium on Si(111) induced by Mg deposition using LEED, STM and ARPES. We found that two new phases, (2√3 × 2√3) (Mg coverage 0.2 ML) and (√3 × √3) (1 ML), are formed. Both phases have 2D nearly-free-electron band structures. The band structure of the (√3 × √3) phase is reproduced by three-atomic-layer models.