A5025229464- Graphene research and applications
- Carbon Nanotubes in Composites
- 2D Materials and Applications
- Diamond and Carbon-based Materials Research
- Fullerene Chemistry and Applications
- Chalcogenide Semiconductor Thin Films
- Graphene and Nanomaterials Applications
- Ion-surface interactions and analysis
- MXene and MAX Phase Materials
- Nanowire Synthesis and Applications
- Molecular Junctions and Nanostructures
- Semiconductor materials and interfaces
- Geochemistry and Elemental Analysis
- Advancements in Battery Materials
- Semiconductor materials and devices
- ZnO doping and properties
- Marine and coastal plant biology
- Metal and Thin Film Mechanics
- Quantum Dots Synthesis And Properties
- Hydrogen embrittlement and corrosion behaviors in metals
- Nanopore and Nanochannel Transport Studies
- Perovskite Materials and Applications
- solar cell performance optimization
- Boron and Carbon Nanomaterials Research
- Metal Extraction and Bioleaching
Tohoku University
2016-2025
Advanced Institute of Materials Science
2023-2025
Nippon Steel (Japan)
2001-2019
Japan Science and Technology Agency
2018-2019
École Nationale des Greffes
2004-2015
Nippon Steel (Germany)
2014-2015
Symbiosis International University
2013
Symbiosis Group
2013
Stanford University
2011
Toyama Prefectural University
2010
Tubular structures of transition metal dichalcogenides (TMDCs) have attracted attention in recent years due to their emergent physical properties, such as the giant bulk photovoltaic effect and chirality-dependent superconductivity. To understand control these it is highly desirable develop a sophisticated method fabricate TMDC tubular with smaller diameters more uniform crystalline orientation. For this purpose, rolling up monolayers into nanoscrolls an attractive approach fabricating...
Understanding the spatial motion of excitons is both fundamental interest and central importance for optoelectrical applications. Here, we have investigated temperature (T) dependence transport dynamics neutral charged (trions) in atomically thin two-dimensional crystals transition-metal dichalcogenide WS2. The can be divided into three ranges, where diffusion governed by thermal activation (≤∼75 K), ionized impurity scattering (∼75 K ≤ T ≤∼200 LO phonon (≥∼200 K). trions a length that over...
Transition metal dichalcogenides (TMDs) exhibit unique properties and potential applications when reduced to one-dimensional (1D) nanoribbons (NRs), owing quantum confinement high edge densities. However, effective growth methods for self-aligned TMD NRs are still lacking. We demonstrate a versatile approach lattice-guided of dense, aligned MoS 2 NR arrays via chemical vapor deposition (CVD) on anisotropic sapphire substrates, without tailored surface steps. This method enables the synthesis...
A transfer-free method for growing carrier-density-controlled graphene directly on a SiO2 substrate has been realized the first time by rapid-heating plasma chemical vapor deposition (RH-PCVD). Using this method, high-quality single-layer sheets with hexagonal domain can be selectively grown between Ni film and substrate. Systematic investigations reveal that relatively thin layer, rapid heating, CVD are critical to success of unique growth. By applying technique, an easy scalable...
We present the first demonstration of nonmagnetic catalyzed synthesis narrow-chirality distributed single-walled carbon nanotubes (SWNTs). Based on systematic investigation using different combinations catalyst types (magnetic or nonmagnetic) and chemical vapor deposition (CVD) methods (thermal CVD (TCVD) plasma (PCVD)), PCVD with under appropriate H(2) concentration is found to be critical as methodological element realizing distribution. Electrical measurements thin film SWNTs produced are...
Abstract Few-layered transition metal dichalcogenides (TMDs) are known as true two-dimensional materials, with excellent semiconducting properties and strong light–matter interaction. Thus, TMDs attractive materials for semitransparent flexible solar cells use in various applications. Hoewver, despite the recent progress, development of a scalable method to fabricate mono- or few-layered remains crucial challenge. Here, we show easy fabrication TMD cell using Schottky-type configuration...
Conventionally, graphene is a poor thermoelectric material with low figure of merit (ZT) 10-4-10-3. Although nanostructuring was proposed to improve the performance graphene, little experimental progress has been accomplished. Here, we carefully fabricated as-grown suspended nanoribbons quarter-micron length and ∼40 nm width. The ratio electrical thermal conductivity enhanced by 1-2 orders magnitude, Seebeck coefficient several times larger than bulk which yielded record-high ZT values up...
We have realized the direct growth of short-length (<100 nm) single-walled carbon nanotubes (SWNTs) with a narrow-chirality distribution by time-programmed plasma chemical vapor deposition (TP-PCVD). Transmission electron microscope and atomic force analyses reveal that very short SWNTs are selectively grown precisely controlling their time on order few seconds. Direct photoluminescence excitation measurements also show chirality is fairly narrow, (7, 6) (8, 4) dominant successfully...
A direct correlation between carrier doping and selective edge functionalization is revealed for graphene treated with a mild NH3 plasma. Raman mapping analysis shows that the D-peak near of sheet selectively increases after plasma treatment. Electrical measurements show Dirac point position nanoribbon device shifts toward negative gate-bias voltage.
Monolayers of transition metal dichalcogenides (TMDs) are an ideal 2D platform for studying a wide variety electronic properties and potential applications due to their chemical diversity. Similarly, single-walled TMD nanotubes (SW-TMDNTs)-seamless cylinders rolled-up monolayers-are 1D materials that can exhibit tunable depending on both chirality composition. However, much less has been explored about geometrical structures variations instability under ambient conditions. Here, the...
Abstract Adding a mechanical degree of freedom to the electrical and optical properties atomically thin materials can provide an excellent platform investigate various optoelectrical physics devices with motion interaction. The large scale fabrication such suspended structures remains challenge. Here we demonstrate wafer-scale bottom–up synthesis graphene nanoribbon arrays (over 1,000,000 nanoribbons in 2 × cm substrate) very high yield 98%). Polarized Raman measurements reveal array have...
The authors report electrical transport properties of p-n junction based on semiconducting single-walled carbon nanotubes (SWCNTs). formation is realized in SWCNTs, which are encapsulated with Fe nanoparticles at low filling fractions. devices exhibit an excellent rectifying behavior, and no current down to 10−14A level flows when the device biased reverse. During measurements performed temperature range from 10to300K, maintain high reproducibility. More importantly, even after exposure air,...
Barren grounds (ground devoid of seaweed beds) in coastal areas present serious environmental problems Japan and around the world. To restore beds on barren ground, a mixture steel slag (hereafter referred to as slag) compost, which included humic substances (HSs), was applied area Mashike (Hokkaido, Japan). Three plots ground were considered. One treated with slag, another combination third plot left untreated (control plot). The types their fresh weights recorded three subsequent years....
In order to understand the effects of plasma parameters on nanotube formation and further controlled growth, we have investigated optimal growth condition using a rf plasma-enhanced chemical vapor deposition method. The magnetic field introduced for magnetron discharge enhances as result plasma-density increment self-bias reduction electrode. It is also found that optimum ion flux bombardment energy key parameter uniform, well-aligned, density-controlled growth.
We have investigated the possibility of using single-walled carbon nanotubes (SWNTs) as infrared energy conversion material based on configuration SWNT/Si heterojunction. The performance solar cells SWNTs has been examined under illumination by light with different wavelengths. Our experimental results confirm that play a critical role in transforming (1550 nm) into electrical energy. encapsulation C60 fullerene inside is found to significantly enhance through adjusting Fermi level SWNTs.
Abstract The very early nucleation stage of a transition metal dichalcogenide (TMD) was directly observed with in-situ monitoring chemical vapor deposition and automated image analysis. Unique dynamics, such as large critical nuclei slow to rapid growth transitions, were during the vapor–liquid–solid (VLS) monolayer tungsten disulfide (WS 2 ). This can be explained by two-step nucleation, also known non-classical in which metastable clusters are formed through aggregation droplets....
Double-walled carbon nanotubes (DWNTs) are filled with ferrocene molecules by a vapour diffusion method for the first time. The as-synthesized ferrocene-filled DWNTs characterized transmission electron microscopy (TEM), energy-dispersive x-ray spectrometry (EDX) and Raman spectroscopy. Electronic properties of double-walled studied fabricating them as channels field-effect transistor (FET) devices. Our results reveal that electronic greatly modified due to charge transfer between DWNTs. In...
Carbon nanowalls (CNWs) are synthesized under pure methane gas (CH4) using helicon plasma-enhanced chemical vapor deposition. CH4 in the discharge is effectively dissociated to hydrogen atoms and hydrocarbon radicals, resulting formation of CNWs on a Ni substrate only from CH4. grown up at high growth rate 18 µm/h.
A photoluminescence (PL) peak has been observed from a monolayer of transition metal dichalcogenide (TMD), which is known to be an ideal 2D semiconductor. The PL appears near the low-energy side neutral free excitons with very sharp width (∼10 meV) at low temperature (83 K). Systematic temperature-dependent measurements reveal that can explained by bound being trapped surface impurities, results in highly localized state for excitons. Since optically detectable, impurity promises have...
Chirality-selective synthesis of single-walled carbon nanotubes (SWNTs) has been a research goal for the last two decades and is still challenging due to difficulty in controlling atomic structure one-dimensional material. Here, we develop an optimized approach chirality species by tuning oxidation degree Co catalyst. Predominant (6,4) SWNTs realized first time. The detailed mechanism investigated through systematic experimental study combined with first-principles calculations, revealing...
Isolated freestanding single-walled carbon nanotubes (SWNTs) have been successfully produced on silicon-based flat substrates using diffusion plasma-enhanced chemical vapour deposition. The quantitative effects of plasma parameters, such as ion density and sheath electric field, the growth tube alignments SWNTs are discussed basis Langmuir probe measurements simple calculations.
Photoluminescence (PL) brightening is clearly observed through the direct morphology transition from isolated to thin bundled vertically- and individually freestanding single-walled carbon nanotubes (SWNTs). On basis of precise spectra analysis equation-based estimation PL time trace, origin consistently explained in terms exciton energy transfer tube bundles. The also revealed obviously depend on SWNT diameters. Only small-diameter rich sample can realize brightening, which be by different...
The authors have an extensive study of photoluminescences for Zn-polar and O-polar faces single-crystalline ZnO bulks. In the photoluminescence (PL) spectra at 10 K, show a common emission feature: neutral donor-bound excitons their longitudinal-optical (LO) phonon replicas are strong free very weak. However, in PL room temperature (RT), extremely different characteristics: intensity face is 30 times larger than that band edge 33 meV redshifted from face. dependence indicates RT closely...