Quasi-Nanbu scheme, a new inter-molecular collision scheme proposed in the previous work, has been extended to diatomic molecules and gas mixtures. Then, the extension has been implemented in a Direct Simulation Monte Carlo (DSMC) model created on a commercial FEM software COMSOL Multiphysics^®. N₂ gas heat conduction between parallel plates and two-dimensional supersonic nozzle flows of gas mixtures are demonstrated as application examples.

TiZrV non-evaporable getter (NEG) coating is being developed at KEK for future light source applications. In order to understand influence of adsorbed gases on TiZrV pumping performance, the TiZrV coated films were characterized by thermal desorption spectroscopy, glow discharge optical emission spectroscopy and pumping speed measurement. TiZrV films adsorb active gases, and among these O₂ is pumped 6–7 times as many as CO. After atmospheric exposure, O₂ and H₂O penetrate over 60 nm in TiZrV films at room temperature. In the activation process, H₂ is released and O atoms diffuse into the TiZrV films. The remaining O atoms hinder the activation, resulting in degradation of the pumping speed.

Large polycyclic aromatic hydrocarbons (PAHs), the so-called nanographenes, are attractive materials for the creation of two- and/or three-dimensional (2D and/or 3D) thin films. However, they exhibit no solubilities in organic solvents and water. To overcome this issue, in the present study, we employed water-soluble micellar capsules consisting of V-shaped amphiphilic molecules. Characteristic dicoronylene and C₉₆H₃₀ adlayers were successfully prepared on Au(111) using the water-soluble micellar capsules. The details on the adlayer structures were clearly revealed by scanning tunneling microscopy imaging with molecular resolutions. The result indicates that our molecular containers method based on the water-soluble micellar capsules can apply to form larger PAH adlayers.

We have investigated the relationship between the electrical properties and the interfacial atomic structures of SiO₂/4H-SiC interfaces, prepared by dry thermal oxidation procedures with 4H-SiC (0001) and 4H-SiC (000-1) substrates, using near-edge extended x-ray absorption fine structure (NEXAFS) spectroscopy and electrical methods. From capacitance-voltage measurements, SiO₂/4H-SiC (000-1) interface exhibited 10 times higher interface state density than SiO₂/4H-SiC (0001) interface. From NEXAFS measurements, we found that C and Si vacancies formed at the SiC side of SiO₂/4H-SiC (0001) and SiO₂/4H-SiC (000-1) interfaces, respectively. Compressive stress at the SiC sides of SiO₂/4H-SiC (0001) and SiO₂/4H-SiC (000-1) interfaces caused decreases in bond lengths. We concluded that a high density of interface states was related to a high interface stress and a high interface roughness.

Graphene is promising for beyond 5G applications with a low environmental load. However, one of the primary challenges in realizing these devices is the scalable growth of high-quality few-layer graphene (FLG) on device-type wafers ; it is difficult to do so while balancing both quality and affordability. We propose a new method for the growth of high-quality FLG on a new template named “hybrid SiC”. The hybrid SiC is produced by bonding a SiC bulk crystal with an affordable device-type wafer and subsequently peeling off the SiC bulk crystal to obtain a single-crystalline SiC thin film on the wafer. The quality of FLG on this hybrid SiC is comparable to that of FLG on SiC bulk crystals. FLG on the hybrid SiC exhibited high carrier mobilities, comparable to those on SiC bulk crystals. Transistors using FLG on the hybrid SiC showed the potential to operate in terahertz frequencies. The proposed method is suited for growing high-quality FLG on desired substrates with the aim of realizing society 5.0 for sustainable development goals.

Chemical identification of individual surface atoms has been achieved by measuring the chemical bonds between tip and surface atoms using atomic force microscopy. On the other hand, the discrimination of chemical species at the tip apex is still a challenging task. Here, we perform the chemical identification of a foremost tip atom using bond energies measured on pre-characterized atomic species on a Si surface. We find that chemically different tips show different trends in the scatter plot of bond energies, and that Pauling's equation for polar covalent bonds well describes those trends. On the basis of this knowledge, in-situ chemical identification becomes possible, which can be applied to a broad range of elements in the periodic table. Using the chemically identified (here, Si and Al) tips, we determine the electronegativity of locally formed silicon oxide solely by experiments previously such determination was difficult without the help of theoretical calculations.

The structures of polymer electrolyte membranes and binders and the distributions of water therein are important for designing new ion-conductive ionomers for polymer electrolyte fuel cells (PEFCs). To aid the understanding of the water distribution, neutron reflectometry was carried out at 80℃ and the relative humidity of 30–80%, simulating the conditions for the PEFC power generation on Nafion^® films formed on SiO₂/Si(100) and Pt/SiO₂/Si(100) substrates. For Nafion films on a native SiO₂ layer, the NR data were fit very well with a 4-layer model parallel to the substrate with different densities of Nafion and water. At the interface between the Nafion film and the SiO₂ substrate, a 1-nm water-rich layer was observed under all conditions. For Nafion films on a Pt layer, the NR data were fit with a 3-layered model. The thin film structures of Nafion were very different on different substrates of SiO₂ and Pt.