Browsing by Author "Ohno, Yutaka"

Now showing 1 - 3 of 3
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    Fast and Ultraclean Approach for Measuring the Transport Properties of Carbon Nanotubes
    (WILEY-V C H VERLAG GMBH, 2020-01-01) Wei, Nan; Laiho, Patrik; Khan, Abu Taher; Hussain, Aqeel; Lyuleeva, Alina; Ahmed, Saeed; Zhang, Qiang; Liao, Yongping; Tian, Ying; Ding, Er Xiong; Ohno, Yutaka; Kauppinen, Esko I.; Department of Applied Physics; NanoMaterials; Helsinki School of Economics; Rice University; Department of Applied Physics; Nagoya University
    In this work, a fast approach for the fabrication of hundreds of ultraclean field-effect transistors (FETs) is introduced, using single-walled carbon nanotubes (SWCNTs). The synthesis of the nanomaterial is performed by floating-catalyst chemical vapor deposition, which is employed to fabricate high-performance thin-film transistors. Combined with palladium metal bottom contacts, the transport properties of individual SWCNTs are directly unveiled. The resulting SWCNT-based FETs exhibit a mean field-effect mobility, which is 3.3 times higher than that of high-quality solution-processed CNTs. This demonstrates that the hereby used SWCNTs are superior to comparable materials in terms of their transport properties. In particular, the on–off current ratios reach over 30 million. Thus, this method enables a fast, detailed, and reliable characterization of intrinsic properties of nanomaterials. The obtained ultraclean SWCNT-based FETs shed light on further study of contamination-free SWCNTs on various metal contacts and substrates.
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    Key factors for ultra-high on/off ratio thin-film transistors using as-grown carbon nanotube networks
    (Royal Society of Chemistry, 2022-06-01) Sun, Yun; Li, Pengpeng; Kauppinen, Esko I.; Sun, Dong Ming; Ohno, Yutaka; Department of Applied Physics; NanoMaterials; CAS - Institute of Metal Research; Nagoya University
    Approximately 30% of as-grown carbon nanotube (CNT) networks are metallic, usually leading to a trade-off between carrier mobility and on/off ratio in CNT thin-film transistors (TFTs). Figuring out the key factors of ultra-high on/off ratio in CNT TFTs should be considerably essential for the development of large-scale electronic devices in the future. Here ultra-high on/off ratios of 107-108 are realized for CNT TFTs with mobility of ∼500 cm2 V−1 s−1. We propose that one of the key factors to achieve the high on/off ratio is a clean CNT thin film without charge traps and doping due to residual dispersant used in conventional solution processes. Moreover, on/off ratio degradation under operation voltage is significantly suppressed by decreasing the diameter of CNTs.
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    ZnO Nanostructures Application in Electrochemistry : Influence of Morphology
    (AMERICAN CHEMICAL SOCIETY, 2021-01-21) Sulciute, Agne; Nishimura, Keita; Gilshtein, Evgeniia; Cesano, Federico; Viscardi, Guido; Nasibulin, Albert G.; Ohno, Yutaka; Rackauskas, Simas; Department of Chemistry and Materials Science; Electrochemical Energy Conversion; Kaunas University of Technology; Nagoya University; Swiss Federal Laboratories for Materials Science and Technology; University of Turin
    The aim of this work was to investigate the influence of morphology on its electrochemical properties by comparing ZnO nanostructures in the forms of tetrapods of different sizes, nanorods, and nanoparticles. ZnO tetrapods were prepared by the combustion method and separated into two fractions by size, ruling out the influence of synthesis conditions. Structural and morphological properties of different ZnO nanostructure morphologies were identified by using various characterization techniques: scanning and transmission electron microscopies (SEM and TEM), X-ray powder diffraction (XRD), nitrogen adsorption/desorption measurements at 77 K, and UV-vis spectroscopy (UV-vis). Analysis of electrochemical properties showed the highest active surface area of 0.095 cm2 and the lowest peak separation value of 61.7 mV for large ZnO tetrapods, which are close to the theoretical values. The correlation between the pore size in different ZnO nanostructures because of packing and their electrochemical properties is established. We expect that the detailed analysis of ZnO nanostructures conducted in this study will be advantageous for future electrochemical and biosensing applications of these materials.