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Because carbon nanotube forest formed by surface decomposition of silicon carbide (CNT forest on SiC) is densely packed and vertically aligned with no entangle parts, it is useful to investigate the electrical properties of dense CNT forest. CNTs atomically bond to SiC substrates, causing good electrical contact for SiC power devices, where the Schottky barrier height is considerably low as ~0.4 eV. CNTs contact with each other in dense CNT forest and contact conductance of CNT/CNT interface can be evaluated as ~108 S cm−2. This value corresponds to the tunneling conductance between electron clouds of adjacent graphene sheets.

The electrical contact properties of silicon carbide (SiC) and carbon nanotubes (CNTs) were measured by conductive atomic force microscopy (C-AFM). A CNT forest was synthesized by SiC surface decomposition. Trenches, which electrically separate the conduction area, were fabricated using a focused ion beam (FIB) without a cover layer, and the resistance of each island was measured by C-AFM. From the dependence of the resistance on the CNT forest island size, the contact resistance between the CNTs and the SiC substrate was measured. By varying the dopant density in the SiC substrate, the Schottky barrier height was evaluated to be ~0.5 eV. This is slightly higher than a previously reported result obtained from a similar setup with a metal covering the CNT forest. We assumed that the damaged region existed in the islands, which is due to the trench formation by the FIB. The commensurate barrier height was obtained with the length of the damaged region assumed to be ~3 μm. Here, we could estimate the resistivity of a CNT/SiC interface without a cover layer. This indicates that a CNT forest on SiC is useful as a brief contact electrode.

We report the thermoelectric properties of Nb-doped (Nd0.55Li0.36)TiO3 bulk ceramics prepared by the conventional sintering method. Superlattice structure present throughout the crystalline grain was observed and a glass-like thermal conductivity (∼2 W/m·K) was obtained. The electrical properties of (Nd0.55Li0.36)TiO3 were improved due to the Ti-site-Nb-doping. The low solid solubility of Nb and the distortion of TiO6 octahedron impaired the electrical performance of Nb-doped (Nd0.55Li0.36)TiO3. The sample with 5 at%Nb gave the maximum ZT value of 0.05 at 650 K. This work is helpful for the design of novel oxide thermoelectric materials.

Understanding of the contact conductivity of carbon nanotubes (CNTs) will contribute to the further application of CNTs for electronic devices, such as thin film transistors whose channel or electrode is made of dispersed CNTs. In this study, we estimated the contact conductivity of a CNT/CNT interface from the in-plane conductivity of an uncapped CNT forest on SiC. Investigation of the electrical properties of dense CNT forests is also important to enable their electrical application. The in-plane conductivity of a dense CNT forest on silicon carbide normalized by its thickness was measured to be 50 S/cm, which is two to three orders of magnitude lower than the conductivity of a CNT yarn. It was also found that both the CNT cap region and the CNT bulk region exhibit in-plane conductivity. The contact conductivity of CNTs was estimated from the in-plane conductivity in the bulk region. Dense and uncapped CNT forest can be approximated by a conductive mesh, in which each conductive branch corresponds to th...

We show that boron-doped epitaxial graphene can be successfully grown by thermal decomposition of a boron carbide thin film, which can also be epitaxially grown on a silicon carbide substrate. The interfaces of B4C on SiC and graphene on B4C had a fixed orientation relation, having a local stable structure with no dangling bonds. The first carbon layer on B4C acts as a buffer layer, and the overlaying carbon layers are graphene. Graphene on B4C was highly boron doped, and the hole concentration could be controlled over a wide range of 2 × 1013 to 2 × 1015 cm-2. Highly boron-doped graphene exhibited a spin-glass behavior, which suggests the presence of local antiferromagnetic ordering in the spin-frustration system. Thermal decomposition of carbides holds the promise of being a technique to obtain a new class of wafer-scale functional epitaxial graphene for various applications.

The synthesis of silver nanoparticles (AgNPs) within the interlayer space of transparent layered titania nanosheet (TNS) films is investigated. A considerable number of silver ions (≈70% against the cation exchange capacity of the TNS) are intercalated in the TNS films using methyl‐viologen‐containing TNSs as a precursor. The silver ion (Ag+)‐containing TNS films are treated with aqueous sodium tetrahydroborate (NaBH4), resulting in a gradual color change to bright blue. Various structural analyses clearly show that crystalline AgNPs are generated within the interlayer space of the TNSs. The NaBH4‐treated films show intense and characteristic near‐infrared (NIR) extinction spectra up to 1800 nm. The stability of the AgNPs within the TNS against oxygen and moisture is also investigated, and 96% and 82% of the AgNPs remain after standing in air for 1 month and 1 year, respectively. The NIR extinctions of the AgNP‐containing TNS films are further extended by employing different preparation procedures, for example, using sintered TNS films as starting materials and irradiating the Ag+‐containing TNSs with ultraviolet (UV) light. The obtained AgNP‐containing TNS films exhibit photochemical activities in the production of hydrogen from ammonia borane under visible‐light irradiation and the decomposition of nitrogen monoxide under UV‐light irradiation.

We have performed density-functional tight-binding simulations mimicking the thermal decomposition of the SiC ( 0 0 0 1 ¯ ) surface to reproduce the experimentally observed growth of either graphene or carbon nanotubes. A graphene-like network was obtained from a layer-by-layer decomposition of the SiC surface. The interaction between graphene and SiC was found to be relatively weak. Meanwhile, carbon nanotubes grew when a five-membered ring was initially formed together with a carbon chain. The simulation results suggest that growth selectivity depends on the overall carbon network connectivity and carbon aggregation speed at the very initial stage of the decomposition process.

Environmental transmission electron microscopy and ultra-high resolution electron microscopic observation using aberration correctors have recently emerged as topics of great interest. The former method is an extension of the so-called in situ electron microscopy that has been performed since the 1970s. Current research in this area has been focusing on dynamic observation with atomic resolution under gaseous atmospheres and in liquids. Since 2007, Nagoya University has been developing a new 1-MV high voltage (scanning) transmission electron microscope that can be used to observe nanomaterials under conditions that include the presence of gases, liquids and illuminating lights, and it can be also used to perform mechanical operations to nanometre-sized areas as well as electron tomography and elemental analysis by electron energy loss spectroscopy. The new instrument has been used to image and analyse various types of samples including biological ones.

In order to achieve waste heat recovery using thermoelectric systems, thermoelectric materials showing high conversion efficiency over wide temperature range and high resistance against oxidation are indispensable. A silicide material with good n-type thermoelectric properties and oxidation resistance has been discovered. The composition and crystal structure of the silicide are found out Mn3Si4Al2 (abbreviated as 342 phase) and hexagonal CrSi2 structure, respectively. Element substitution of Mn with 3d transition metals is succeeded. Enhancement of Seebeck coefficient is observed in a Cr-substituted sample. The maximum dimensionless thermoelectric figure of merit ZT is 0.3 at 573 K in air for the Mn2.7Cr0.3Si4Al2 sample. Electrical resistivity of the Mn3Si4Al2 bulk sample holds constant value for 48 h at 873 K in air. This is due to formation of oxide passive layer on the surface of the bulk sample. The 342 phase is a promising n-type material with a good oxidation resistance in the middle temperature range of 500-800 K.

The substitutional doping of magnesium into the host layers (TiS2), calcium and strontium into phonon barrier layers (BiS) was attempted to improve the thermoelectric performance of (BiS)1.2(TiS2)2 misfit layer sulfides by decreasing the carrier concentration. The substitutional doping did reduce the carrier concentration; however, the Seebeck coefficient decreased slightly due to the decrease in the effective mass of carrier electrons. Meanwhile, the lattice thermal conductivity was increased by the formation of an ordered or commensurate structure.

The carbon nanotubes (CNTs) on 6H-SiC and Si-doped CNTs on 6H-SiC were analyzed by hard x-ray photoelectron spectroscopy to identify the chemical bonding character of the doped Si in the CNT layer. We performed the depth profiling of the sample by changing photoelectron's take-off-angle (TOA). The spectral component associated with the doped Si is clearly seen in the Si 1s photoelectron spectra of Si-doped CNTs on 6H-SiC. The Si 1s peak shifts toward lower kinetic energy side from TOA = 80° (bulk-sensitive) to 8° (surface-sensitive), which implies the formation of the sp2-like structure in Si-doped CNTs. [DOI: 10.1380/ejssnt.2011.54]

We have measured low-temperature ac impedance of films of closely-packed, highly-aligned carbon nanotubes prepared by thermal decomposition of silicon carbide wafers. The measurement was performed on films with the thickness (the length of the nanotubes) ranging from 6.5 to 65 nm. We found that the impedance rapidly decreases with the frequency. This can be interpreted as resulting from the electric transport via capacitive coupling between adjacent nanotubes. We also found numbers of sharp spikes superposed on frequency vs. impedance curves, which presumably represent resonant frequencies seen in the calculated conductivity of random capacitance networks. Capacitive coupling between the nanotubes was reduced by the magnetic field perpendicular to the films at 8.2 mK, resulting in the transition from negative to positive magnetoresistance with an increase of the frequency.

Graphene is a single-layer carbon sheet with a honeycomb structure, and bilayer graphene consists of two graphene sheets with AB stacking. In trilayer graphene, the third graphene sheet has two possible stacking sequences, A or C, when it is overlaid on bilayer graphene. It has been theoretically predicted that trilayer graphene exhibits a variety of novel electronic properties with/without a Dirac-cone band, depending on the stacking sequence. In this regard, trilayer graphene has a high potential for widening the capability of graphene-based electronic devices. However, the difficulty of selective fabrication has hindered the progress of research. Here, we report the first success in the selective fabrication of quasi-free-standing trilayer graphene with ABA or ABC stacking grown epitaxially on hydrogen-terminated silicon carbide. Angle-resolved photoemission spectroscopy (ARPES) clearly demonstrated that our trilayer graphene with ABA stacking has a massless Dirac-like band near the Fermi level, while that with ABC stacking shows a parabolic non-Dirac-like band dispersion. Strict control of temperature and pressure during annealing is shown to be crucial for controllably stacking graphene by a team in Japan. Graphene is a single layer of carbon atoms in a hexagonal arrangement. When two graphene layers are stacked, some carbon atoms in the top layer sit above the center of each hexagon of the lower layer. A third layer either sits directly aligned with the bottom layer (ABA stacking) or is again displaced from the previous two (ABC stacking). These two arrangements exhibit very different properties. Takashi Takahashi from Tohoku University and colleagues deterministically created either ABA or ABC trilayer graphene by first annealing bilayer graphene on a hydrogen-terminated silicon carbide substrate. They found that the alignment of the third layer is determined by the temperature and pressure of this anneal. Quasi-free-standing trilayer graphene with ABA or ABC stacking was selectively synthesized on hydrogen-terminated silicon carbide. The electronic structure was investigated by angle-resolved photoemission spectroscopy. While ABA graphene exhibits a massless Dirac-cone-like band at the K point in the Brillouin zone, ABC graphene was found to show a parabolic non-Dirac-like band. The present success in selective fabrication of ABA and ABC graphene would open a pathway toward graphene-based nano electronic devices with variable layer number and stacking sequence such as high-speed transistor and photodetector.

We have investigated the length-dependence of the in-plane electrical resistivity of vertically aligned and highly dense carbon nanotube (CNT) films that were dense enough to conduct electrons. The in-plane conductivity is well accounted for by a combination of inter-tube hopping (variable range hopping, VRH) and graphitic conduction. VRH conduction was dominant in the thinner CNT films, and the films showed negative temperature dependence of resistivity. The dimension of the VRH component varied depending on the CNT length. In the thicker CNT films, the graphitic conduction appeared, and then, the localization length spread, leading to the positive temperature dependence of resistivity. This behavior can be explained by the presence of a labyrinthine arrangement of graphene walls among aligned CNTs, which was confirmed by transmission electron microscopy observations.

To realize the solid materials with higher emission quantum yield from the rhodamine 6G (R6G) monomers, typical laser-dye, we hybridized both alkyltrimethylammonium (CnTMA+) and R6G cations into th...

Adherence of carbon nanotube film made by surface decomposition of SiC was studied. For this purpose we carried out scratch tests in nano- and microscale. By microscratch test, it was found that adherence at the interface was higher for CNT films with shorter CNTs and CNTs were not broken at the middle but removed from the interface. To clarify the dominant force (shear force or moment of force) which caused different adherence, we also carried out nanoscratch test by using AFM. In nanoscratch, AFM tip made of diamond coated silicon applied shear force to CNT films from lateral direction. And there was no significant change of adherence by lateral force (shear force at the interface). We conclude that bending-induced moment of force is dominant on the interface strength of CNT films.

The effects of oxygen on the early stage of carbon nanocap and nanotube growth by surface decomposition of 6H–SiC(000-1) were investigated, using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Our results showed that the presence of oxygen enhances the decomposition of the SiC surface, promoting carbon nanocap and nanotube growth. We also observed active-to-passive oxidation transition below 10− 1 Pa, which is consistent with the pressure–temperature phase diagram previously estimated from experimental results above 10− 1 Pa.

Formation of nanosized cap structures on a thermally treated 6H–SiC(0 0 0 −1) substrate was investigated using atomic-resolution ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). After removal of surface oxides by heating under UHV, clusters of carbon particles 1–2 nanometer in diameter were formed on the SiC surface at 1150 °C. Upon heating above 1150 °C, the carbon nanoparticles in the clusters merged, forming nanosized cap structures, which subsequently transformed into carbon nanotubes (CNTs). The clusters of nanosized carbon particles are thought to be the precursors of carbon nanocaps, and their sizes are strongly related to the sizes of CNT caps forming on the SiC surface.

Zigzag-type carbon nanotubes have been selectively produced by surface decomposition of a well-polished SiC single crystal. The SiC wafer was heated to 1500 °C at a very small heating rate under vacuum. Transmission electron microscopy (TEM) and electron diffraction patterns revealed that almost all the well-aligned carbon nanotubes formed perpendicular to the SiC (0 0 0 −1) surface were double-walled and of zigzag type. The results of high-resolution electron microscopy (HREM) indicate that the zigzag type structure evolves from the Si–C hexagonal networks in the SiC crystal by the collapse of carbon layers remaining after the process of decomposition.

In order to apply carbon nanotubes (CNTs) as the anode materials of a solid-state Li-ion secondary battery, the surface modifications of the CNT thin film formed by the SiC surface decomposition method were carried out by the Ar-ion sputtering method. Then, we observed the CNT film by field emission scanning electron and measured the Raman scattering spectra of the CNT film in order to evaluate the effect of Ar-ion bombardments on the CNT film.

Graphene has a negative thermal expansion coefficient; that is, when heated, the graphene lattice shrinks. On the other hand, the substrates typically used for graphene growth, such as silicon carbide, have a positive thermal expansion coefficient. Hence, on cooling graphene on SiC, graphene expands but SiC shrinks. This mismatch will physically break the atomic bonds between graphene and SiC. We have demonstrated that a graphenelike buffer layer on SiC can be converted to a quasifreestanding monolayer graphene by a rapid-cooling treatment. The decoupling of graphene from the SiC substrate was actually effective for reducing the electric carrier scattering due to interfacial phonons. In addition, the rapidly cooled graphene obtained in this way was of high-quality, strain-free, thermally stable, and strongly hole doped. This simple, classical, but quite novel technique for obtaining quasifreestanding graphene could open a new path towards a viable graphene-based semiconductor industry.

Ultrafine spherical particles of γ-Al 2 O 3 containing 4 at% magnesium and pure γ-Al 2 O 3 were prepared by evaporating metal Al in air. Consequently, both particles were heated at 1400°C for 6 h in a vacuum. TEM observations showed that the Mg-doped γ-Al 2 O 3 particles were much more stable than the pure γ-Al 2 O 3 particles. The role of Mg atoms on the stability is discussed mainly based on the results obtained by high-resolution electron microscopy and energy dispersive X-ray spectroscopy.

The Raman spectra of carbon nanotubes (CNTs) formed on a 6H–SiC(0001) C-face substrate by surface decomposition were acquired using a 1064 nm Nd:YAG laser as the excitation source. Intense radial-breathing-mode Raman bands were successfully detected under resonant excitation from CNTs formed by the surface decomposition of SiC. Fine CNTs having diameters between 0.7 and 1.3 nm were observed on SiC after heating at 1700 °C in a vacuum electric furnace. These diameters are considerably smaller than those previously observed for CNTs grown by this technique.

Nanosized cap structures on a thermally treated 6H–SiC(0001) substrate were investigated using atomic-resolution ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). Hexagonal carbon networks, partly composed of pentagons, were clearly observed on the surface of the cap structures for a sample annealed at 1250°C, in which carbon nanotubes (CNTs) had negligibly grow into the SiC substrate. Comparing their sizes and shapes with those annealed at 1350°C, the cap structures were considered to be the initial state of carbon nanotube (CNT) growth which determines the tube diameters of the final grown CNTs.

Diamond particles were synthesized by a filament assisted CO 2 laser induced CVD technique on a silicon substrate in a hydrogen environment. The deposition was carried out using a gaseous mixture of CH 4 and H 2 , which flowed through a beam generator equipped with a tiny orifice and positioned above a refractory filament. The filament was separated 25 mm from the substrate and a cw-CO 2 laser was used to irradiate the substrate's surface. The presence of diamond particles on the substrate was confirmed by Raman Spectroscopy and Scanning Electron Microscope. The factors that hindered the synthesis of a continuous diamond film were investigated from the results of EDS, TEM analysis, HREM analysis, and Electron Diffraction Patterns.

The formation of large-area homogeneous graphene on a C-terminated SiC (000$\overline{1}$) surface was achieved via decomposition of the SiC (000$\overline{1}$) surface covered with an ultrathin but much more stable TiC layer than the reactive SiC(000$\overline{1}$). By heating the SiC (000$\overline{1}$) surface with a mixed powder of TiO${}_{2}$ and carbon at 1500--1550 \ifmmode^\circ\else\textdegree\fi{}C in vacuum, an extremely homogeneous, epitaxial 0.75-nm-thick TiC(111) layer was grown on the SiC(000$\overline{1}$) surface over a millimeter-scale area. Graphitization of the TiC-masked SiC surface led to the growth of high-quality graphene layers, which consist of TiC- and SiC-derived carbon. High-resolution transmission electron microscopy revealed the presence of disordered stacking of graphene layers on SiC through an amorphous layer at the interface. This unique method will promise further progress of relatively high carrier mobility of graphene formed on the SiC (000$\overline{1}$) surface.

We observed and analyzed the behavior of platinum nanoparticles (PtNPs) supported on aligned-carbon nanotubes (CNTs) at high temperatures by X-ray photoelectron spectroscopy and high-resolution transmission electron microscope observations. We found that the PtNPs moved toward the inner-side along each CNT on which they were deposited. The mechanism of this behavior is related to the redox reaction of Pt with the carbon atoms in the CNT. We also performed in-situ observation of this process at a high temperature using an environmental transmission electron microscope under an oxygen atmosphere. We found that the PtNPs penetrated down into a high-density aligned CNT forest along the tube axis and that the PtNPs changed their shape to fit the structure of the CNTs during their movement.

The structures of bimetallic CuPt particles in freshly reduced and outgassed CuPt/NaY zeolites were characterized by extended X-ray absorption fine structure (EXAFS) at the Cu K-edge and Pt L 3 -edge. In order to understand the effect of copper on the coordinative environment of platinum, reduced Cu/NaY and Pt/NaY were also studied. It is found that the structure of CuPt bimetallic particles is dependent on the atomic ratio of Cu and Pt in the zeolites

Characteristic tribological properties, such as nonlinearity of the friction force-normal load curve, high coefficient of friction, and good wear-resistant performance were observed on densely packed, vertically aligned carbon nanotubes (CNTs) with different diameters and lengths using atomic force microscopy. Shorter and thicker CNTs were found to have higher coefficients of friction. The observed properties were attributed to the nonlinear elastic property of the CNTs caused by buckling.

It has been reported that carbon nanotubes (CNTs) were formed through the decomposition of SiC(000-1) surfaces by heating in a vacuum. By this growth technique, well aligned zigzag-type CNTs can be selectively formed without any catalysts and the diameters of the CNTs are fairly uniform. Moreover, this growth technique has an advantage in fabrication of CNT devices, since CNTs grow into the inside of SiC, facilitating the application of semiconductor process. So far, we have reported that ambient oxygen enhances the CNT growth rate [1]. However, the optimum oxygen pressure has never been investigated enough. It has also been reported that SiO2 layer is formed on SiC surface after annealing under high oxygen pressure [2]. In this study, we investigated the relation between surface oxide formation and CNT growth under various annealing conditions. After HF etching, 6H-SiC(000-1) (Carbon-face) samples were introduced into an ultra-high vacuum (UHV) chamber and annealed at various temperatures between 800 and 1250°C. During the annealing, oxygen partial pressure was controlled by supply of oxygen gas. The oxygen pressure was set between 10-4 and 1 Pa. For comparison, we also annealed several samples under UHV (10-6 Pa). Scanning tunneling microscopy (STM) observation and X-ray photoelectron spectroscopy (XPS) measurements were carried out to analyze their surface structures and chemical species. It was observed that the surface decomposition of SiC had occurred after annealing at 800°C under UHV, and carbon nanocaps were formed on the SiC surface at 1200°C, which subsequently transformed into CNTs. When oxygen pressure was below 10-2 Pa, the nanocap formation was observed between 1150 and 1200°C irrespective of oxygen pressure. However, at 1 Pa of oxygen pressure, SiO2 layer was observed on the SiC surface after annealing at 1200°C and no carbon nanocaps were observed. These results indicate that it is necessary to anneal SiC below 1 Pa to form CNT, although the presence of oxygen enhances CNT formation below 10-3 Pa. The boundary between the active oxidation and the passive oxidation in SiC oxidation estimated from our results was well consistent with previous studies for SiC oxidation under higher oxygen pressure (>1 Pa)[2]. From our results, in order to grow CNT effectively, it is important to minutely control oxygen pressure.

Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3 × 1018 cm−3 was estimated to be ∼1.3 × 10−4 Ω cm2 and the Schottky barrier height of the CNT/SiC contact was in the range of 0.40–0.45 eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices.

A film of well-oriented carbon nanotubes was produced by sublimation decomposition of silicon carbide at 1700 °C by using YAG laser heating in a transmission electron microscope (TEM). The processes of SiC decomposition and the formation of carbon nanotubes were observed successively by high-resolution electron microscopy (HREM). Carbon nanotubes were mostly oriented along the [111] direction on the (111) surface plane of β-SiC single crystal. The interface between them was observed by HREM.

Formation process of nanosized cap structures on a thermally treated 6H-SiC(000-1) substrate was investigated using atomic-resolution ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). After formation of clusters of carobon particles 1-2 nanometer in diameter at 1150°C, these nanoparticles merged, forming nanosized cap structures. Hexagonal carbon networks, partly composed of pentagons, were clearly observed on the surface of the cap structures for a sample annealed above 1200°C. A model for the formation of carbon nanocaps on 6H-SiC(000-1) was proposed.

To use carbon nanotubes (CNTs) as anode material for the solid-state thin-film Li-ion rechargeable battery, the tubes are preferred to be aligned perpendicular to a substrate and the CNT thin film to have a smooth surface. Using an Ar-ion sputtering technique, we carried out the surface modifications of the CNT thin film prepared by the SiC surface decomposition method. In order to evaluate the surface modification, the surface and cross section of the modified CNT film were investigated by field-emission scanning electron microscopy and atomic force microscopy. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Environmental transmission electron microscopy has recently emerged as topics of great interest as well as ultra-high resolution electron microscopy using aberration correctors. Current research in this area has been focusing on dynamic observation with atomic resolution under gaseous atmospheres and in liquids. Nagoya University has been developing a new 1-MV high voltage (scanning) transmission electron microscope, which can be used to observe nano-materials under conditions that include the presence of gases, liquids and illuminating lights, and it can be also used to perform mechanical operations to nm-sized areas as well as electron tomography and elemental analysis by electron energy loss spectroscopy.

Graphene, a one-atom-layer carbon material, can be grown by thermal decomposition of SiC. On Si-terminated SiC(0001), graphene nucleates at steps and grows layer-by-layer, and as a result a homogeneous monolayer or bilayer can be obtained. We demonstrate this mechanism both experimentally and theoretically. On the C-face (000), multilayer graphene nucleates not only at steps, but also on the terraces. These differences reflect the distinct differences in the reactivity of these faces. Due to its high quality and structural controllability, graphene on SiC{0001} surfaces will be a platform for high-speed graphene device applications.

Unusually high concentration of C60/C70 was discovered in a coal sample from China. Extensive analysis including TEM analysis suggests a surprising occurrence of the fullerenes in nature by shock heating, which we suggest to have been generated by coal gas explosion in the underground.

The atomic-scale carbon rearrangement into graphene by the thermal decomposition of SiC (0001) was simulated by the density-functional tight-binding technique. By decomposing the terrace of the SiC (0001) surface, the carbon chains formed a three-dimensional structure, because the carbon atoms are released by losing their original contacts to silicon atom. On the other hand, in the step model, the silicon atoms at the step-edge act as trapping sites for the released carbon atoms, and the carbon network effectively nucleated and expanded. After nucleation at the step, graphene can grow by the further decomposition together with retreat of the step.

A silicide material with a good n-type thermoelectric property has been discovered. This silicide possesses a composition of Mn3−xCrxSi4Al2 (0 ≤ x ≤ 0.7) and hexagonal CrSi2 structure. The a- and c-cell parameters decrease with increasing the amount of Cr substitution. The absolute values of Seebeck coefficient and electrical resistivity increase by Cr substitution up to 573 K because of reduction of carrier density. The dimensionless thermoelectric figure of merit ZT reaches 0.21 at 773 K for a non Cr substituted sample at the Mn site and 0.30 at 573 K for a Cr substituted one with x = 0.3. Since oxide passive layer is formed around the surface, electrical resistivity measured at 873 K is constant for 2 days in air, which indicates good oxidation resistance in air of this material. The Mn3−xCrxSi4Al2 is a promising n-type material with a good oxidation resistance in the middle temperature range. A thermoelectric module consisting of 64 pairs of legs has been fabricated using MnSi1.7 and non Cr substitute...

We grew graphene by thermal decomposition of B(4)C and investigated its features by high-resolution transmission electron microscope observations. At temperatures higher than 1600 °C in a vacuum, B(4)C decomposes and graphene forms epitaxially on its surface. The number and the morphology of the graphene layers depend on the surface orientation. An electron diffraction technique revealed the presence of a superstructure with a two-times larger unit cell, which is consistent with the structure of BC(3). We have directly confirmed boron in the graphene layers by electron energy loss spectroscopy measurements and boron-mapping experiments.

High-temperature quantum chemical molecular dynamics simulations have been performed on model systems of thin SiC crystal surfaces with two graphene sheets placed on top of either C or Si face. In agreement with experiment, we find that (a) the C-face-attached graphene layer warps readily to form small diameter, stable nanocaps, suitable for further perpendicular growth of nanotubes, (b) the Si-face-attached graphene sheet does not readily wrap and forms more volatile Si-graphene bonds, and (c) C face nanocaps appear to anneal to dome-shape structures with zigzag chirality.