The Division of Microbeam Analysis, the Japan Society of Vacuum and Surface Science, publishes the Database for Auger and Secondary Electron Spectra online (https://www.jvss.jp/division/mba/sedb/). These spectral data were measured with an SI traceable cylindrical mirror analyzer developed by Keisuke Goto (absolute measurement system). The database body stores measurement data and spectra of 56 materials and 47 materials as an appendix. This paper reports the concept and characteristics of the absolute measurement system and introduces the electron spectra database.
For realizing single molecular devices using metal-molecule-metal junction, it is necessary to fabricate a steady conductive bridge-structure. Recently, our group reported a molecular bridging method using migration of gold atoms on static nanogap electrodes. It was proposed that repeated cycles of single-molecular-bridging and breaking between benzene-di-thiolate (BDT) molecules and nanogap electrodes using this method. In this paper, to confirm the bridging condition during the cycles, current-voltage curves in each state were investigated. This result indicates that characteristic orbital energies of BDT were revealed while observed conductance was close with 11.0 mG0. On the other hand, when the observed conductance was below 11.0 mG0, the magnitude of estimated orbital energies was the similar as that using nanogap electrodes which were not covered by any molecules, which explained that direct tunneling conduction between Au electrodes was dominant. This clearly indicates that cycles between molecular-bridging and disconnection were realized using static nanogap structures.
Germanene, a graphene-like honeycomb crystal of germanium, has been attracting immense attention owing to its exotic properties such as a tunable bandgap and high carrier mobility. However, the fabrication of germanene-based electronic devices is difficult owing to its chemical instability. To overcome this problem, we proposed and developed a new method of germanene growth at graphene/Ag(111) and hexagonal boron nitride/Ag(111) interfaces. The grown germanene at the interfaces was stable in air and uniform over the entire area covered with a van der Waals (vdW) material. As an important finding, a vdW interface provides a nanoscale platform for growing germanene similarly to that in vacuum, while this cannot be achieved with a typical oxide interface (Al2O3). We believe that our work is of significantly importance not only for the growth of germanene but also for the fabrication of future germanene-based electronic devices.
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.
Photoelectron angular distribution from the valence state of π-conjugated molecules on the surface has been studied to clarify the molecular orientation quantitatively with multiple scattering theory of photoelectron emission intensity. After developing the photoelectron emission techniques together with molecular thin-film preparations, a novel concept of photoemission tomography enables to investigate the electronic states in depth to understand the molecular functional properties in a sense of orbital. The article reviews the recent progress and development of the photoelectron momentum microscope related techniques for molecular science.
X-ray microscopy and time-resolved observation using synchrotron radiation are reviewed based on recent reports on in situ observation of cracking and degradation of structural materials. X-ray microscopy can provide three-dimensional images of microstructures and chemical states with a high spatial resolution down to 50 nm. In situ observation using X-ray microscopy successfully revealed crack initiation and propagation in carbon fiber reinforced plastic (CFRP) while a stress was applied to the specimen. X-ray microscopy was applied to ceramic coating or CFRP to perform chemical-state mapping, which is essential for understanding the trigger sites of degradation. In situ observation of time-resolved X-ray diffraction and/or X-ray absorption spectroscopy was carried out with a time resolution down to a few nanosecond by synchronizing an X-ray pulse with a laser pulse. This technique was applied to investigate the mechanism of deformation and fracture or structural phase transitions of metal and alloys after the laser shock.
Further improvements and development of new polymer electrolyte materials are required to achieve the target values stated in NEDO (New Energy and Industrial Technology Development Organization) roadmap for the fuel cell and hydrogen technology developments. If the final goal is broken down into the performance of polymer electrolyte materials, minor changes to materials that have already been developed or are on the market will not be able to meet that demand. A major technical breakthrough will be required in the next 10 years, and a new concept will be required to achieve it. After showing the research background of polymer electrolyte membranes, this report overviews the current issues of polymer electrolyte membranes, especially the response to the NEDO roadmap for fuel cell and hydrogen technology developments.
Inelastic electron tunneling spectroscopy (IETS) combined with scanning tunneling microscopy (STM) allows us to acquire vibrational signals at surfaces. In STM-IETS, a tunneling electron from the STM tip excites vibrations whenever the energy of the tunneling electron exceeds the vibrational energies. This opens up an inelastic channel in parallel with the elastic one and gives rise to an increase/decrease of the conductivity. As a consequence, a pair of peak and dip shows up at the bias voltages with respect to the Fermi level corresponding to the energy of vibrational energy. Until recently, the application of STM-IETS was limited to the localized vibration of single atoms and molecules adsorbed on surfaces. In principle, STM-IETS should be capable of detecting collective lattice dynamics, i.e., phonons. In this paper, I will introduce the theory of STM-IETS measurement for a metal surface and the application of this theory for surface phonons on Cu(110).
The advancements of Si electronics from the past to the present are reviewed and the future technological trends are discussed based on the semiconductor roadmap. The development of the heterogeneous integration is also discussed.
As a post-OLED (organic light emitting diode) device, expectations are rising for an organic semiconductor laser diode (OSLD), which is the ultimate current injection device. In order to realize OSLD, the achievement of high current density of several kA cm－2 and the development of laser molecules exhibiting ultra-low threshold has been required. This paper introduces the recent progress in molecular design for laser molecules aimed for OSLDs.
Plasma catalysis is gathering attentions for its unique characters in chemical reactivity and product selectivity. Various applications have been suggested and demonstrated. When catalysts are located inside the plasma zone, bilateral interactions occur which are generally complicated to get full understanding of the detailed steps. Nevertheless, a lot of experimental results have been filed up for various chemical reactions (decomposition, synthesis, partial redox). Notwithstanding the progress during the last decades, however, the understanding of the working mechanism is still in early stage. As a representative model reaction, room temperature oxidation of CO was compared for the conventional thermal catalysis, plasma-driven catalysis, and ozone-assisted catalysis. The effect of different catalyst, reaction mechanism, and catalyst regeneration was discussed. In this review, the current progress to understand the bilateral interactions of plasma and catalyst, literature survey, and some of future perspective will be presented.
Progress of novel fabrications for functional surfaces using various shapes and materials are introduced such as subwavelength optics, biomimetic, electric devices, related to capability of advanced nanoimprint technology
We demonstrate the cold emission of ytterbium atomic vapors from ytterbium oxide irradiated with a simple ultraviolet diode laser. Slow atoms are trapped by a magneto-optical trap using a dipole-allowed strong transition at 399 nm. Accompanying phenomenon of the emission of white light from the irradiated ytterbium oxide sample is preliminary investigated. This method will open the way towards a compact and transportable optical lattice clock.
In this review, we summarize recent progress achieved in on-surface bottom-up growth of graphene nanoribbons (GNRs) with well-defined edges. First, we show the simulation results suggesting that a GNR backward diode with GNR heterojunction can outperform the state-of-the-art diodes owing to their negligible junction capacitance. The major challenge required for achieving high-performance GNR diodes is low contact resistance and well-defined GNR heterojunction. The second part of this review is dedicated to our recent works on GNR heterojunctions by modifying electronic states by edge-functionalization. It was revealed that the important design policies for precursors are as follows : molecular design avoiding intramolecular steric hinderance upon polymerization, precursor design considering dehydrogenation path, and precursor design considering intramolecular side reaction. We also demonstrate our preliminary results of GNR-FET, which suggest that wider GNRs with narrower band gap is required for the electronic devices.
We have developed scanning tunneling potentiometry (STP) operating in ultrahigh vacuum conditions, which provides us a surface topography and the corresponding electrochemical potential distribution simultaneously in nanometer scale special resolution and µV-level potential sensitivity under a lateral electrical current flowing parallel to the sample surface. Using this setup, we have successfully performed an STP measurement on the Si(111)-7×7 reconstructed surface, which holds metallic surface states. Our observation indicates that not only steps but also phase boundaries of the Si(111)-7×7 surface work as an electrical resistance impeding the conductance through the surface states. From the evaluation of the ratio of conductivity across the one-dimensional line defects to that of the terrace on the Si(111)-7×7 surface, the conductivity of the phase boundary is found five times that of the monolayer-height step.
Three types of semi-empirical equation for calculating the gas flow rate in a cylindrical tube of arbitrary length-to-diameter ratio are proposed. The solutions of these equations cover all flow regimes from molecular flow to critical flow or subcritical flow via intermediate flow, viscous laminar flow, and turbulent flow. In addition, the calculation procedure is straightforward because it does not require selecting a suitable equation based on the Knudsen number, Reynolds number, and Mach number. Comparing the solutions of the proposed equations with reported results from experiments and computer simulations shows good agreement within 30%.
横田 泰之, 早澤 紀彦, 楊 波, 数間 恵弥子, Francesca C. I. Catalan, 金 有洙
Microscopic studies on electrolyte solution / electrode interfaces provide the most fundamental information not only for understanding the electric double layer formed at the interfaces but also for designing sophisticated electrochemical (EC) devices. In this study, we developed tip-enhanced Raman spectroscopy (TERS), which is based on an electrochemical scanning tunneling microscope (EC-STM), and demonstrated electrochemical TERS (EC-TERS) measurements of benzenethiol monolayers on Au(111). A specially-designed cell enables us to carry out reproducible EC, EC-STM, and EC-TERS measurements, which indicates consistent results among these techniques for the oxidative desorption of the benzenethiol monolayers.
Electret or permanent electrical charge is used as a part of mechano-electric energy conversion system for vibrational energy harvesting device. Microscopic capacitors are produced by silicon micromachining or MEMS (microelectromechanical systems) fabrication process, and the surfaces are turned into impurity-rich silicon oxide, which is later processed to make an electret by displacing the impurity ions by the same mechanism as the anodic bonding. The built-in potential of the electret is used to produce electrical current through the electrostatic induction when the movable electrode is periodically shaken by the external vibrations. In this article, the fabrication processes for the electret as well as the MEMS vibrational energy harvester are discussed. The fundamental characteristics of the energy harvesters are reported, along with a demonstration result as an autonomous powerpack for an IoT (internet-of-things) type wireless sensor node.
Soil is defined as a mixture of weathering products of rocks (sand, silt, and clay) and humus (or soil organic matter) derived from plant or animal. World soils are divided into 12 groups and their distribution is not uniform. Soil degradation includes soil acidification in humid region, salinization in arid regions, and loss of soil organic matter in both regions. Minimum tillage or optimized fallow systems can minimize loss of soil organic matter and improve soil fertility. Understanding of complex soil system is required for food supply and human survival.
Digital Annealer developed by Fujitsu is a new architecture to solve “combinatorial optimization problems” at high speed with digital circuit inspired by quantum phenomena. The features are stable operation with digital circuit at room temperature, easy miniaturization, and easy mapping more complex problems with a fully-connected architecture. The Digital Annealer is easy to apply actual problems and contributes to customers in a wide range of businesses, including drug discovery, chemistry, manufacturing, transportation, finance, and logistics. In this article, we explain the fundamental of the Digital Annealer including the speedup technique. We also introduce an application to the material development using the Digital Annealer. The Digital Annealer is used to evaluate the structural similarity of the flavor molecules. We found that the molecules with high structural similarity show a similar flavor. We also extracted the common substructure of molecules having the similar flavor, which is considered to be the key structure of the flavor.