The high sensitivity of secondary ion mass spectrometry (SIMS) allows isotope imaging and the high spatial precision has a potential for the localization of isotopes corresponding to the ultrastructure of cell components. This paper reviews a study in which transfers of carbon and nitrogen from the fungus in a symbiotic orchid protocorm were analyzed, combining an isotope tracer experiment, sample preparation for transmission electron microscopy, and SIMS cellular imaging. The results showed that, 13C and15N transferred from young and senescent hyphae, and in the plant cells, they were localized differently in individual cells and organelles, depending on the colonization status (the presence or absence of fungal structures and the early or late developmental stage of the fungal structure). Stable isotope imaging at the cellular level provides new insights into cellular functions of the endosymbiosis.
The development of dendrimer reactors opened the new research field by the production of metal subnanoparticles with definite atomicities. These precise platinum subnanoparticles exhibited the true catalytic properties, which have been hidden by the conventional synthetic method due to the substantial size distribution. One significant finding was that the several subnanoparticles exhibited much higher oxygen reduction reaction catalytic activity than the conventional platinum nanoparticle (∼3 nm). The result was completely opposite to the common notice that the most catalytically active particle size is ca. 3 nm. Despite of this inconsistence, it was finally concluded that some subnanoparticles have specific surfaces which have higher activities originated from the unique geometric structures.
A method for debonding polyimide film and ultra-thin glass from glass substrate is proposed. The method is based on the surface activated bonding approach extended to a modified bonding process using Si nano-adhesion layer. The surfaces of both polyimide film and the glass substrate are activated by Si nano-adhesion layer deposited in vacuum and bonded in situ at room temperature whereas only the ultra-thin glass surface is treated with Si nano-adhesion layer, and bonded in vacuum to glass substrate after exposure to N2 gas. Even after a thermal treatment such as TFT process over 400 to 500°C, they can be debonded by mechanical peeling at room temperature.
The real time observation of nanoscale deformation is a significant step toward understanding the mechanisms of friction, wear and lubrication. Our experimental system of a micromachine combined with a TEM enabled us to measure the deformation, force and actual contact area of a single Ag and Fe asperity. The experimental results provided insight into one of the parameters that determines the frictional coefficient. Furthermore, we demonstrated that the energy loss associated with a separation event is correlated with the increase in total surface energy of the two surfaces formed here after the separation of the nano-contact.
Low energy ion scattering spectroscopy is a powerful tool for the analysis of the topmost surface composition and structure. Low energy atom scattering spectroscopy is a quite useful tool for the analysis of the topmost insulator surfaces, as well. Because the primary beams of low energy atom scattering are electrically neutral. This report provides some of the basic principles relating to the interaction between low energy particles (ions/atoms) and topmost surfaces. Due to the large amount of research carried out in this field, selected materials are shown in this report.
We introduce a state-of-the-art patterning process developed by new patterning technology using Atomic Layer Deposition (ALD) towards 5/7 nm generation. In the patterning process, critical dimension (CD) shrink technique without CD loading is one of the key requirements. However, in the conventional CD shrink technique, CD loading canʼt be solved in principle. To overcome this issue, by integrating ALD process into the etching flow, we developed a new CD shrink technique without causing CD loading. Furthermore, CD shrink amount can be precisely controlled by the number of ALD cycles while keeping the excellent CD shrink uniformity across a wafer. This is obtained by utilizing a conformal layer with characteristics of ALDʼs self-limiting reaction, which is independent of the pattern variety.
Development of artificial photosynthesis is prospected on the basis of its history, the three milestones in late 20th century, and recent advances in biological approach, molecular catalysts, and semiconductors chemistry. Photon-flux-density problem to be resolved in getting through one of the bottleneck issues is discussed as well as renewable energy factor (REF) as one of the most crucial points to be considered even in the early stage of fundamental research.
小野田 穣, Martin ONDRÁČEK, Pavel JELÍNEK, 杉本 宜昭
Electronegativity is one of the fundamental concepts in chemistry. Despite its importance, the experimental determination has been limited only to ensemble-averaged techniques. Here, we report a new methodology to evaluate the electronegativity of individual surface atoms by atomic force microscopy. By measuring bond energies on the surface atoms using different tips, we found characteristic linear relations between the bond energies of different chemical species. Using Paulingʼs equation for polar covalent bond, we successfully quantify their electronegativity values. Moreover, we demonstrate that the method is sensitive to variation of the electronegativity of given atomic species on a surface due to different chemical environments. Our findings open up new ways of analyzing surface chemical reactivity in atomic scale.
Ultrafast photoexcitation of the spin-polarized Dirac surface state in the topological insulator Sb2Te3 was investigated by using time- and angle-resolved two-photon photoemission spectroscopy combined with tunable mid-infrared pump pulses. It was revealed that mid-infrared pump permits a direct excitation between the occupied and unoccupied part of the surface Dirac-cone. Moreover, the direct optical coupling induces asymmetric transient populations in the surface states at ±k||, which reflects a macroscopic photoexcited electric surface current. By observing the decay of the asymmetric population and its temperature dependence, the ultrafast dynamics of the surface current was visualized in the momentum space.
We have fabricated alkali metal (Li, Rb, Cs) and alkaline-earth metal (Ca) intercalated bilayer graphene on SiC substrate, and characterized them by low-energy electron diffraction, angle-resolved photoemission spectroscopy, and 4-point-probe measurements. We observed a free-electron-like state in the center of the Brillouin zone, called “interlayer state”, as well as the folded π/π* bands in Rb-, Cs-, and Ca-intercalated graphene, while it was absent in Li counterpart. Ca-intercalated bilayer graphene shows the zero-resistance below 4K, indicative of the two-dimensional superconductivity. These results suggest that the interlayer state plays an important role for the superconductivity in intercalated bilayer graphene.
Spin-polarized scanning tunneling microscopy (SP-STM), which is one of the most developed probe microscopy last decades, provides spin-contrasted surface images in nano- and atomic-scale spatial resolutions. This paper introduces the technique based on our recent results performed on manganese thin films on a W(110) substrate and cobalt nano-islands formed on a Ag(111) substrate. We also provide some tips to establish SP-STM in laboratories.
Core-level photoelectron diffraction provides element-specific atomic structure information. Forward focusing peaks (FFPs) indicate the directions of atoms surrounding a photoelectron emitter atom. When a core level is excited by circularly polarized light, angular momentum of light is transferred to an emitted photoelectron, which can be confirmed by the parallax shift measurement of FFP direction. Here I report the new observation and quantitative analysis of the angular momentum transfer from light to Auger electrons, and compare them with the photoelectron cases. Angularmomentum-polarized Cu LMM Auger electrons at the L absorption threshold, where the excited core electron is trapped at the conduction band, were detected. By setting an analyzer at the corresponding position in the FFP direction, the Auger electron with a specific angular momentum can be selectively detected. In the case of magnetic materials, circular dichroism in the X-ray absorption intensity was observed together with angular momentum transfer (parallax shift) effect.
Spin-orbit interaction in solids can be utilized for controlling spin-dependent transport phenomena. To realize them, we focus on thin films and interfaces of iridium (Ir) oxides since electron conduction there is dominated by 5d electrons with strong spin-orbit interaction. The first example is the inverse spin Hall effect, which converts a spin current into an electric voltage. The performance of IrO2 as a spin-current detector is better than those of noble metals. The second is the topological Hall effect originating from magnetic skyrmions. The epitaxial bilayers consisting of SrRuO3 and SrIrO3 enable us to generate skyrmions through artificially broken inversion symmetry at the interfaces. These results can be a step toward future spintronics.