start-ver=1.4 cd-journal=joma no-vol=13 cd-vols= no-issue=1 article-no= start-page=537 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230111 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Semiconductor-metal transition in Bi2Se3 caused by impurity doping en-subtitle= kn-subtitle= en-abstract= kn-abstract=Doping a typical topological insulator, Bi2Se3, with Ag impurity causes a semiconductor-metal (S-M) transition at 35 K. To deepen the understanding of this phenomenon, structural and transport properties of Ag-doped Bi2Se3 were studied. Single-crystal X-ray diffraction (SC-XRD) showed no structural transitions but slight shrinkage of the lattice, indicating no structural origin of the transition. To better understand electronic properties of Ag-doped Bi2Se3, extended analyses of Hall effect and electric-field effect were carried out. Hall effect measurements revealed that the reduction of resistance was accompanied by increases in not only carrier density but carrier mobility. The field-effect mobility is different for positive and negative gate voltages, indicating that the E-F is located at around the bottom of the bulk conduction band (BCB) and that the carrier mobility in the bulk is larger than that at the bottom surface at all temperatures. The pinning of the E-F at the BCB is found to be a key issue to induce the S-M transition, because the transition can be caused by depinning of the E-F or the crossover between the bulk and the top surface transport. en-copyright= kn-copyright= en-aut-name=UchiyamaTakaki en-aut-sei=Uchiyama en-aut-mei=Takaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TakaiAkihisa en-aut-sei=Takai en-aut-mei=Akihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=ZhiLei en-aut-sei=Zhi en-aut-mei=Lei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MiuraAkari en-aut-sei=Miura en-aut-mei=Akari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=OtaHiromi en-aut-sei=Ota en-aut-mei=Hiromi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=SugimotoKunihisa en-aut-sei=Sugimoto en-aut-mei=Kunihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=MatsuiFumihiko en-aut-sei=Matsui en-aut-mei=Fumihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=KimuraKoji en-aut-sei=Kimura en-aut-mei=Koji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=HayashiKouichi en-aut-sei=Hayashi en-aut-mei=Kouichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= en-aut-name=UenoTeppei en-aut-sei=Ueno en-aut-mei=Teppei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=15 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=16 ORCID= en-aut-name=AkimitsuJun en-aut-sei=Akimitsu en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=17 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=18 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=7 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=8 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=9 en-affil=Advanced Science Research Center, Okayama University kn-affil= affil-num=10 en-affil=Faculty of Science and Engineering, Kindai University kn-affil= affil-num=11 en-affil=Department of Nanotechnology for Sustainable Energy, Kwansei Gakuin University kn-affil= affil-num=12 en-affil=Institute for Molecular Science, UVSOR Synchrotron Facility kn-affil= affil-num=13 en-affil=Department of Physical Science and Engineering, Nagoya Institute of Technology kn-affil= affil-num=14 en-affil=Department of Physical Science and Engineering, Nagoya Institute of Technology kn-affil= affil-num=15 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=16 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=17 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=18 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=6 article-no= start-page=5495 end-page=5501 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220131 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Evaluation of Effective Field-Effect Mobility in Thin-Film and Single-Crystal Transistors for Revisiting Various Phenacene-Type Molecules en-subtitle= kn-subtitle= en-abstract= kn-abstract=The magnitude of the field-effect mobility mu of organic thin-film and single-crystal field-effect transistors (FETs) has been over-estimated in certain recent studies. These reports set alarm bells ringing in the research field of organic electronics. Herein, we report a precise evaluation of the mu values using the effective field-effect mobility, mu(eff), a new indicator that is recently designed to prevent the FET performance of thin-film and single-crystal FETs based on various phenacene molecules from being overestimated. The transfer curves of a range of FETs based on phenacene are carefully categorized on the basis of a previous report. The exact evaluation of the value of mu(eff) depends on the exact classification of each transfer curve. The transfer curves of all our phenacene FETs could be successfully classified based on the method indicated in the aforementioned report, which made it possible to evaluate the exact value of mu(eff) for each FET. The FET performance based on the values of mu(eff) obtained in this study is discussed in detail. In particular, the mu(eff) values of single-crystal FETs are almost consistent with the mu values that were reported previously, but the mu(eff) values of thin-film FETs were much lower than those previously reported for mu, owing to a high absolute threshold voltage, vertical bar V-th vertical bar. The increase in the field-effect mobility as a function of the number of benzene rings, which was previously demonstrated based on the mu values of single-crystal FETs with phenacene molecules, is well reproduced from the mu(eff) values. The FET performance is discussed based on the newly evaluated mu(eff) values, and the future prospects of using phenacene molecules in FET devices are demonstrated. en-copyright= kn-copyright= en-aut-name=ZhangYanting en-aut-sei=Zhang en-aut-mei=Yanting kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OkamotoHideki en-aut-sei=Okamoto en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=21 cd-vols= no-issue= article-no= start-page=093056 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190924 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Superconductivity in a new layered triangular-lattice system Li2IrSi2 en-subtitle= kn-subtitle= en-abstract= kn-abstract=We report on the crystal structure and superconducting properties of a novel iridium-silicide, namely Li2IrSi2. It has a Ag2NiO2-type structure (space group R-3m) with the lattice parameters a = 4.028 30(6) ? and c = 13.161 80(15) ?. The crystal structure comprises IrSi2 and double Li layers stacked alternately along the c-axis. The IrSi2 layer includes a two-dimensional Ir equilateral-triangular lattice. Electrical resistivity and static magnetic measurements revealed that Li2IrSi2 is a type-II superconductor with critical temperature (Tc) of 3.3 K. We estimated the following superconducting parameters: lower critical field Hc1(0) ~ 42 Oe, upper critical field Hc2(0) ~ 1.7 kOe, penetration depth 0 ~ 265 nm, coherence length 0 ~ 44 nm, and Ginzburg?Landau parameter GL ~ 6.02. The specific-heat data suggested that superconductivity in Li2IrSi2 could be attributed to weak-coupling Cooper pairs. en-copyright= kn-copyright= en-aut-name=HoriganeK en-aut-sei=Horigane en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakeuchiK en-aut-sei=Takeuchi en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HyakumuraD en-aut-sei=Hyakumura en-aut-mei=D kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HorieR en-aut-sei=Horie en-aut-mei=R kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=SatoT en-aut-sei=Sato en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MuranakaT en-aut-sei=Muranaka en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KawashimaK en-aut-sei=Kawashima en-aut-mei=K kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=IshiiH en-aut-sei=Ishii en-aut-mei=H kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=KubozonoY en-aut-sei=Kubozono en-aut-mei=Y kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=OrimoS en-aut-sei=Orimo en-aut-mei=S kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=IsobeM en-aut-sei=Isobe en-aut-mei=M kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=AkimitsuJ en-aut-sei=Akimitsu en-aut-mei=J kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University, kn-affil= affil-num=2 en-affil=Graduate School of natural science and technology, Okayama University kn-affil= affil-num=3 en-affil=Department of Physics and Mathematics, Aoyama Gakuin University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Institute for Materials Research, Tohoku University kn-affil= affil-num=6 en-affil=Department of Engineering Science, University of Electro-Communications kn-affil= affil-num=7 en-affil=Department of Physics and Mathematics, Aoyama Gakuin University kn-affil= affil-num=8 en-affil=National Synchrotron Radiation Research Center kn-affil= affil-num=9 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=10 en-affil=Institute for Materials Research, Tohoku University kn-affil= affil-num=11 en-affil=National Institute for Materials Science (NIMS) kn-affil= affil-num=12 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= en-keyword=supreconductivity kn-keyword=supreconductivity en-keyword=iridium-silicide kn-keyword=iridium-silicide en-keyword=spin?orbit coupling kn-keyword=spin?orbit coupling END start-ver=1.4 cd-journal=joma no-vol=10 cd-vols= no-issue=45 article-no= start-page=26686 end-page=26692 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200716 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A new protocol for the preparation of superconducting KBi2 en-subtitle= kn-subtitle= en-abstract= kn-abstract=A superconducting KBi2 sample was successfully prepared using a liquid ammonia (NH3) technique. The temperature dependence of the magnetic susceptibility (M/H) showed a superconducting transition temperature (Tc) as high as 3.6 K. In addition, the shielding fraction at 2.0 K was evaluated to be 87%, i.e., a bulk superconductor was realized using the above method. The Tc value was the same as that reported for the KBi2 sample prepared using a high-temperature annealing method. An X-ray diffraction pattern measured based on the synchrotron X-ray radiation was analyzed using the Rietveld method, with a lattice constant, a, of 9.5010(1) ? under the space group of Fd[3 with combining macron]m (face-centered cubic, no. 227). The lattice constant and space group found for the KBi2 sample using a liquid NH3 technique were the same as those reported for KBi2 through a high-temperature annealing method. Thus, the superconducting behavior and crystal structure of the KBi2 sample obtained in this study are almost the same as those for the KBi2 sample reported previously. Strictly speaking, the magnetic behavior of the superconductivity was different from that of a KBi2 sample reported previously, i.e., the KBi2 sample prepared using a liquid NH3 technique was a type-II like superconductor, contrary to that prepared using a high-temperature annealing method, the reason for which is fully discussed. These results indicate that the liquid NH3 technique is effective and simple for the preparation of a superconducting KBi2. In addition, the topological nature of the superconductivity for KBi2 was not confirmed. en-copyright= kn-copyright= en-aut-name=LiHuan en-aut-sei=Li en-aut-mei=Huan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=WangYanan en-aut-sei=Wang en-aut-mei=Yanan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NishiyamaSaki en-aut-sei=Nishiyama en-aut-mei=Saki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YangXiaofan en-aut-sei=Yang en-aut-mei=Xiaofan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=TaguchiTomoya en-aut-sei=Taguchi en-aut-mei=Tomoya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MiuraAkari en-aut-sei=Miura en-aut-mei=Akari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=SuzukiAi en-aut-sei=Suzuki en-aut-mei=Ai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=ZhiLei en-aut-sei=Zhi en-aut-mei=Lei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KambeTakashi en-aut-sei=Kambe en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=LiaoYen-Fa en-aut-sei=Liao en-aut-mei=Yen-Fa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=IshiiHirofumi en-aut-sei=Ishii en-aut-mei=Hirofumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=7 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=8 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=9 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=10 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=11 en-affil=Department of Physics, Okayama University kn-affil= affil-num=12 en-affil=National Synchrotron Radiation Research Center kn-affil= affil-num=13 en-affil=National Synchrotron Radiation Research Center kn-affil= affil-num=14 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=10 cd-vols= no-issue=52 article-no= start-page=31547 end-page=31552 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200826 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Facile synthesis of picenes incorporating imide moieties at both edges of the molecule and their application to n-channel field-effect transistors en-subtitle= kn-subtitle= en-abstract= kn-abstract=Picene derivatives incorporating imide moieties along the long-axis direction of the picene core (Cn-PicDIs) were conveniently synthesized through a four-step synthesis. Photochemical cyclization of dinaphthylethenes was used as the key step for constructing the picene skeleton. Field-effect transistor (FET) devices of Cn-PicDIs were fabricated by using ZrO2 as a gate substrate and their FET characteristics were investigated. The FET devices showed normally-off n-channel operation; the averaged electron mobility () was evaluated to be 2(1) ~ 10?4, 1.0(6) ~ 10?1 and 1.4(3) ~ 10?2 cm2 V?1 s?1 for C4-PicDI, C8-PicDI and C12-PicDI, respectively. The maximum value as high as 2.0 ~ 10?1 cm2 V?1 s?1 was observed for C8-PicDI. The electronic spectra of Cn-PicDIs in solution showed the same profiles irrespective of the alkyl chain lengths. In contrast, in thin films, the UV absorption and photoelectron yield spectroscopy (PYS) indicated that the lowest unoccupied molecular orbital (LUMO) level of Cn-PicDIs gradually lowered upon the elongation of the alkyl chains, suggesting that the alkyl chains modify intermolecular interactions between the Cn-PicDI molecules in thin films. The present results provide a new strategy for constructing a high performance n-channel organic semiconductor material by utilizing the electronic features of phenacenes. en-copyright= kn-copyright= en-aut-name=GuoYuxin en-aut-sei=Guo en-aut-mei=Yuxin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshiokaKaito en-aut-sei=Yoshioka en-aut-mei=Kaito kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=TaniFumito en-aut-sei=Tani en-aut-mei=Fumito kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=GotoKenta en-aut-sei=Goto en-aut-mei=Kenta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=OkamotoHideki en-aut-sei=Okamoto en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Institute for Materials Chemistry and Engineering, Kyushu University kn-affil= affil-num=6 en-affil=Institute for Materials Chemistry and Engineering, Kyushu University kn-affil= affil-num=7 en-affil=Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=8 cd-vols= no-issue=22 article-no= start-page=7422 end-page=7435 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200418 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Synthesis of [7]phenacene incorporating tetradecyl chains in the axis positions and its application in field-effect transistors en-subtitle= kn-subtitle= en-abstract= kn-abstract=Field-effect transistors (FETs) were fabricated using a new type of phenacene molecule, 3,12-ditetradecyl[7]phenacene ((C14H29)2-[7]phenacene), and solid gate dielectrics or an electric double layer (EDL) capacitor with an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate (bmim[PF6])). The new molecule, (C14H29)2-[7]phenacene, was efficiently synthesized via the Mallory photoreaction. Its crystal structure and electronic properties were determined, using X-ray diffraction, scanning tunneling microscopy/spectroscopy (STM and STS), absorption spectroscopy, and photoelectron yield spectroscopy, which showed a monoclinic crystal lattice (space group P21 (no. 4)) and an energy gap of ?3.0 eV. The STM image clearly showed the molecular structure of (C14H29)2-[7]phenacene, as well as the closed molecular stacking, indicative of a strong fastener effect between alkyl chains. The X-ray diffraction pattern of thin films of (C14H29)2-[7]phenacene formed on a SiO2/Si substrate suggested that the molecule stood on the surface with an inclined angle of 30 with respect to the normal axis of the surface. The FET properties were recorded in two-terminal measurement mode, showing p-channel normally-off characteristics. The averaged values of field-effect mobility, , were 1.6(3) cm2 V?1 s?1 for a (C14H29)2-[7]phenacene thin-film FET with a SiO2 gate dielectric and 6(4) ~ 10?1 cm2 V?1 s?1 for a (C14H29)2-[7]phenacene thin-film EDL FET with bmim[PF6]. Thus, higher FET performance was obtained with an FET using a thin film of (C14H29)2-[7]phenacene compared to parent [7]phenacene. This study could pioneer an avenue for the realization of high-performance FETs through the addition of alkyl chains to phenacene molecules. en-copyright= kn-copyright= en-aut-name=OkamotoHideki en-aut-sei=Okamoto en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KozasaKeiko en-aut-sei=Kozasa en-aut-mei=Keiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=WangYanan en-aut-sei=Wang en-aut-mei=Yanan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=PanYong-He en-aut-sei=Pan en-aut-mei=Yong-He kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=YenYu-Hsiang en-aut-sei=Yen en-aut-mei=Yu-Hsiang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=HoffmannGermar en-aut-sei=Hoffmann en-aut-mei=Germar kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=TaniFumito en-aut-sei=Tani en-aut-mei=Fumito kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=GotoKenta en-aut-sei=Goto en-aut-mei=Kenta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Department of Physics & Center for Quantum Technology, National Tsing Hua University kn-affil= affil-num=7 en-affil=Department of Physics & Center for Quantum Technology, National Tsing Hua University kn-affil= affil-num=8 en-affil=Department of Physics & Center for Quantum Technology, National Tsing Hua University kn-affil= affil-num=9 en-affil=Institute for Materials Chemistry and Engineering, Kyushu University kn-affil= affil-num=10 en-affil=Institute for Materials Chemistry and Engineering, Kyushu University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=3 article-no= start-page=036001 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200316 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Inhomogeneous superconductivity in thin crystals of FeSe1-xTex (x=1.0, 0.95, and 0.9) en-subtitle= kn-subtitle= en-abstract= kn-abstract=We investigated the temperature dependence of resistivity in thin crystals of FeSe1-xTex (x = 1.0, 0.95, and 0.9), though bulk crystals with 1.0 x 0.9 are known to be non-superconducting. With decreasing thickness of the crystals, the resistivity of x = 0.95 and 0.9 decreases and reaches zero at a low temperature, which indicates a clear superconducting transition. The anomaly of resistivity related to the structural and magnetic transitions completely disappears in 55- to 155-nm-thick crystals of x = 0.9, resulting in metallic behavior in the normal state. Microbeam x-ray diffraction measurements were performed on bulk single crystals and thin crystals of FeSe1-xTex. A significant difference of the lattice constant, c, was observed in FeSe1-xTex, which varied with differing Te content (x), and even in crystals with the same x, which was mainly caused by inhomogeneity of the Se/Te distribution. It has been found that the characteristic temperatures causing the structural and magnetic transition (T-t), the superconducting transition (T-c), and the zero resistivity (T-c(zero)) are closely related to the value of c in thin crystals of FeSe1-xTex. en-copyright= kn-copyright= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SendaMegumi en-aut-sei=Senda en-aut-mei=Megumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=ImaiYasuhiko en-aut-sei=Imai en-aut-mei=Yasuhiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KimuraShigeru en-aut-sei=Kimura en-aut-mei=Shigeru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=NojiTakashi en-aut-sei=Noji en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=KoikeYoji en-aut-sei=Koike en-aut-mei=Yoji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Department of Nanotechnology for Sustainable Energy, Kwansei Gakuin University kn-affil= affil-num=6 en-affil=Japan Synchrotron Radiation Research Institute (JASRI) kn-affil= affil-num=7 en-affil=Japan Synchrotron Radiation Research Institute (JASRI) kn-affil= affil-num=8 en-affil=Department of Applied Physics, Tohoku University kn-affil= affil-num=9 en-affil=Department of Applied Physics, Tohoku University kn-affil= affil-num=10 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= en-keyword=iron-based superconductor kn-keyword=iron-based superconductor en-keyword=thin crystals kn-keyword=thin crystals en-keyword=microbeam XRD kn-keyword=microbeam XRD END start-ver=1.4 cd-journal=joma no-vol=9 cd-vols= no-issue= article-no= start-page=4009 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=201938 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Synthesis of the extended phenacene molecules, [10]phenacene and [11]phenacene, and their performance in a field-effect transistor en-subtitle= kn-subtitle= en-abstract= kn-abstract= The [10]phenacene and [11]phenacene molecules have been synthesized using a simple repetition of Wittig reactions followed by photocyclization. Sufficient amounts of [10]phenacene and [11]phenacene were obtained, and thin-film FETs using these molecules have been fabricated with SiO2 and ionic liquid gate dielectrics. These FETs operated in p-channel. The averaged measurements of field-effect mobility, <>, were 3.1(7)?~?10-2 and 1.11(4)?~?10-1?cm2 V-1 s-1, respectively, for [10]phenacene and [11]phenacene thin-film FETs with SiO2 gate dielectrics. Furthermore, [10]phenacene and [11]phenacene thin-film electric-double-layer (EDL) FETs with ionic liquid showed low-voltage p-channel FET properties, with <> values of 3(1) and 1(1)?cm2 V-1 s-1, respectively. This study also discusses the future utility of the extremely extended -network molecules [10]phenacene and [11]phenacene as the active layer of FET devices, based on the experimental results obtained. en-copyright= kn-copyright= en-aut-name=OkamotoHideki en-aut-sei=Okamoto en-aut-mei=Hideki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=TakabayashiYasuhiro en-aut-sei=Takabayashi en-aut-mei=Yasuhiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=YenPaul Yu-Hsiang en-aut-sei=Yen en-aut-mei=Paul Yu-Hsiang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=LiangLuo Uei en-aut-sei=Liang en-aut-mei=Luo Uei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=ChouChia-Wei en-aut-sei=Chou en-aut-mei=Chia-Wei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=HoffmannGermar en-aut-sei=Hoffmann en-aut-mei=Germar kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=GohdaShin en-aut-sei=Gohda en-aut-mei=Shin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=SuginoHisako en-aut-sei=Sugino en-aut-mei=Hisako kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=LiaosYen-Fa en-aut-sei=Liaos en-aut-mei=Yen-Fa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=IshiiHirofumi en-aut-sei=Ishii en-aut-mei=Hirofumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= affil-num=1 en-affil= Department of Chemistry, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil= Department of Chemistry, Okayama University kn-affil= affil-num=6 en-affil=Department of Physics, National Tsing Hua University kn-affil= affil-num=7 en-affil=Department of Physics, National Tsing Hua University kn-affil= affil-num=8 en-affil=Department of Physics, National Tsing Hua University kn-affil= affil-num=9 en-affil=Department of Physics, National Tsing Hua University kn-affil= affil-num=10 en-affil=NARD Co Ltd kn-affil= affil-num=11 en-affil=NARD Co Ltd kn-affil= affil-num=12 en-affil=National Synchrotron Radiation Center kn-affil= affil-num=13 en-affil=National Synchrotron Radiation Center kn-affil= affil-num=14 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=9 cd-vols= no-issue= article-no= start-page=5376 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=2019329 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fermi level tuning of Ag-doped Bi2Se3 topological insulator en-subtitle= kn-subtitle= en-abstract= kn-abstract=The temperature dependence of the resistivity (rho) of Ag-doped Bi2Se3 (AgxBi2-xSe3) shows insulating behavior above 35 K, but below 35 K, rho suddenly decreases with decreasing temperature, in contrast to the metallic behavior for non-doped Bi2Se3 at 1.5-300 K. This significant change in transport properties from metallic behavior clearly shows that the Ag doping of Bi2Se3 can effectively tune the Fermi level downward. The Hall effect measurement shows that carrier is still electron in AgxBi2-xSe3 and the electron density changes with temperature to reasonably explain the transport properties. Furthermore, the positive gating of AgxBi2-xSe3 provides metallic behavior that is similar to that of non-doped Bi2Se3, indicating a successful upward tuning of the Fermi level. en-copyright= kn-copyright= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=UchiyamaTakaki en-aut-sei=Uchiyama en-aut-mei=Takaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OtaHiromi en-aut-sei=Ota en-aut-mei=Hiromi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UenoTeppei en-aut-sei=Ueno en-aut-mei=Teppei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=FujiwaraHirokazu en-aut-sei=Fujiwara en-aut-mei=Hirokazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=TerashimaKensei en-aut-sei=Terashima en-aut-mei=Kensei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=YokoyaTakayoshi en-aut-sei=Yokoya en-aut-mei=Takayoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=MatsuiFumihiko en-aut-sei=Matsui en-aut-mei=Fumihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=AkimitsuJun en-aut-sei=Akimitsu en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil= Advanced Science Research Centre, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=7 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=8 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=9 en-affil=Graduate School of Materials Science, Nara Institute of Science and Technology kn-affil= affil-num=10 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=11 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=12 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=97 cd-vols= no-issue=9 article-no= start-page=094505 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180309 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Pressure dependence of superconductivity in low- and high-T-c phases of (NH3)(y)NaxFeSe en-subtitle= kn-subtitle= en-abstract= kn-abstract= We prepared two superconducting phases, which are called glow-Tc phaseh and ghigh-Tc phaseh of (NH3)yNaxFeSe showing Tcfs of 35 and 44 K, respectively, at ambient pressure, and studied the superconducting behavior and structure of each phase under pressure. The Tc of the 35 K at ambient pressure rapidly decreases with increasing pressure up to 10 GPa, and it remains unchanged up to 22 GPa. Finally, superconductivity was not observed down to 1.4 K at 29 GPa, i.e., Tc < 1.4K. The Tc of the 44 K phase also shows a monotonic decrease up to 15 GPa and it weakly decreases up to 25 GPa. These behaviors suggest no pressure-driven high-Tc phase (called gSC-IIh) between 0 and 25 GPa for the low-Tc and high-Tc phases of (NH3)yNaxFeSe, differing from the behavior of (NH3)yCsxFeSe,which has a pressure-driven high-Tc phase (SC-II) in addition to the superconducting phase (SC-I) observed at ambient and low pressures. The Tc-c phase diagram for both low-Tc and high-Tc phases shows that the Tc can be linearly scaled with c (or FeSe plane spacing), where c is a lattice constant. The reason why a pressure-driven high-Tc phase (SC-II) was found for neither low-Tc nor high-Tc phases of (NH3)yNaxFeSe is fully discussed, suggesting a critical c value as the key to forming the pressure-driven high-Tc phase (SC-II). Finally, the precise Tc-c phase diagram is depicted using the data obtained thus far from FeSe codoped with a metal and NH3 or amine, indicating two distinct Tc-c lines below c = 17.5A . en-copyright= kn-copyright= en-aut-name=TeraoTakahiro en-aut-sei=Terao en-aut-mei=Takahiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YangXiaofan en-aut-sei=Yang en-aut-mei=Xiaofan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MiaoXiao en-aut-sei=Miao en-aut-mei=Xiao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ZhengLu en-aut-sei=Zheng en-aut-mei=Lu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MiyazakiTakafumi en-aut-sei=Miyazaki en-aut-mei=Takafumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=YamaokaHitoshi en-aut-sei=Yamaoka en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=IshiiHirofumi en-aut-sei=Ishii en-aut-mei=Hirofumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=LiaoYen-Fa en-aut-sei=Liao en-aut-mei=Yen-Fa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Laboratory for Surface science, Okayama University kn-affil= affil-num=7 en-affil=RIKEN SPring-8 Center kn-affil= affil-num=8 en-affil=National Synchrotron Radiation Research Center kn-affil= affil-num=9 en-affil=National Synchrotron Radiation Research Center kn-affil= affil-num=10 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= en-keyword=Superconductors kn-keyword=Superconductors en-keyword=2-dimensional systems kn-keyword=2-dimensional systems en-keyword=4-terminal techniques kn-keyword=4-terminal techniques en-keyword=Pressure effects kn-keyword=Pressure effects en-keyword=X-ray diffraction kn-keyword=X-ray diffraction END start-ver=1.4 cd-journal=joma no-vol=3 cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2013 dt-pub=20130413 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electric double-layer capacitance between an ionic liquid and few-layer graphene en-subtitle= kn-subtitle= en-abstract= kn-abstract=Ionic-liquid gates have a high carrier density due to their atomically thin electric double layer (EDL) and extremely large geometrical capacitance C-g. However, a high carrier density in graphene has not been achieved even with ionic-liquid gates because the EDL capacitance C-EDL between the ionic liquid and graphene involves the series connection of C-g and the quantum capacitance C-q, which is proportional to the density of states. We investigated the variables that determine C-EDL at the molecular level by varying the number of graphene layers n and thereby optimising C-q. The C-EDL value is governed by C-q at n, 4, and by C-g at n > 4. This transition with n indicates a composite nature for C-EDL. Our finding clarifies a universal principle that determines capacitance on a microscopic scale, and provides nanotechnological perspectives on charge accumulation and energy storage using an ultimately thin capacitor. en-copyright= kn-copyright= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil= kn-affil=Okayama Univ, Surface Sci Res Lab affil-num=2 en-affil= kn-affil=Okayama Univ, Surface Sci Res Lab affil-num=3 en-affil= kn-affil=Okayama Univ, Surface Sci Res Lab affil-num=4 en-affil= kn-affil=SPring 8, Japan Synchrotron Radiat Res Inst affil-num=5 en-affil= kn-affil=Okayama Univ, Surface Sci Res Lab END start-ver=1.4 cd-journal=joma no-vol=88 cd-vols= no-issue=9 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2012 dt-pub=20120930 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Superconductivity in (NH3)(y)Cs0.4FeSe en-subtitle= kn-subtitle= en-abstract= kn-abstract=Alkali-metal-intercalated FeSe materials, (NH3)(y)M0.4FeSe (M: K, Rb, and Cs), have been synthesized using the liquid NH3 technique. (NH3)(y)Cs0.4FeSe shows a superconducting transition temperature (T-c) as high as 31.2 K, which is higher by 3.8 K than the T-c of nonammoniated Cs0.4FeSe. The T(c)s of (NH3)(y)K0.4FeSe and (NH3)(y)Rb0.4FeSe are almost the same as those of nonammoniated K0.4FeSe and Rb0.4FeSe. The T-c of (NH3)(y)Cs0.4FeSe shows a negative pressure dependence. A clear correlation between T-c and lattice constant c is found for ammoniated metal-intercalated FeSe materials, suggesting a correlation between Fermi-surface nesting and superconductivity. en-copyright= kn-copyright= en-aut-name=ZhengLu en-aut-sei=Zheng en-aut-mei=Lu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IzumiMasanari en-aut-sei=Izumi en-aut-mei=Masanari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SakaiYusuke en-aut-sei=Sakai en-aut-mei=Yusuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TakabayashiYasuhiro en-aut-sei=Takabayashi en-aut-mei=Yasuhiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KambeTakashi en-aut-sei=Kambe en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=OnjiTaiki en-aut-sei=Onji en-aut-mei=Taiki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=ArakiShingo en-aut-sei=Araki en-aut-mei=Shingo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=KobayashiTatsuo C. en-aut-sei=Kobayashi en-aut-mei=Tatsuo C. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KimJungeun en-aut-sei=Kim en-aut-mei=Jungeun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= affil-num=1 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=2 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=3 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=4 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=5 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=6 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci affil-num=7 en-affil= kn-affil=Okayama Univ, Dept Phys affil-num=8 en-affil= kn-affil=Okayama Univ, Dept Phys affil-num=9 en-affil= kn-affil=Okayama Univ, Dept Phys affil-num=10 en-affil= kn-affil=Okayama Univ, Dept Phys affil-num=11 en-affil= kn-affil=RIKEN, SPring Ctr 8, Japan Synchrotron Radiat Res Inst affil-num=12 en-affil= kn-affil=RIKEN, SPring Ctr 8, Japan Synchrotron Radiat Res Inst affil-num=13 en-affil= kn-affil=Okayama Univ, Res Lab Surface Sci END start-ver=1.4 cd-journal=joma no-vol=82 cd-vols= no-issue=19 article-no= start-page=195114-1 end-page=195114-5 dt-received= dt-revised= dt-accepted= dt-pub-year=2010 dt-pub=20101110 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electronic structure of pristine and K-doped solid picene: Nonrigid band change and its implication for electron-intramolecular-vibration interaction en-subtitle= kn-subtitle= en-abstract= kn-abstract=We use photoemission spectroscopy to study electronic structures of pristine and K-doped solid picene. The valence band spectrum of pristine picene consists of three main features with no state at the Fermi level (EF) while that of K-doped picene has three structures similar to those of pristine picene with new states near EF, consistent with the semiconductor-metal transition. The K-induced change cannot be explained with a simple rigid-band model of pristine picene but can be interpreted by molecular-orbital calculations considering electron-intramolecular-vibration interaction. Excellent agreement of the K-doped spectrum with the calculations points to importance of electron-intramolecular-vibration interaction in K-doped picene. en-copyright= kn-copyright= en-aut-name=OkazakiH en-aut-sei=Okazaki en-aut-mei=H kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=WakitaT en-aut-sei=Wakita en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MuroT en-aut-sei=Muro en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KajiY en-aut-sei=Kaji en-aut-mei=Y kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=LeeX en-aut-sei=Lee en-aut-mei=X kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MitamuraH en-aut-sei=Mitamura en-aut-mei=H kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KawasakiN en-aut-sei=Kawasaki en-aut-mei=N kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=KubozonoY en-aut-sei=Kubozono en-aut-mei=Y kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=YamanariY en-aut-sei=Yamanari en-aut-mei=Y kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=KambeT en-aut-sei=Kambe en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KatoT en-aut-sei=Kato en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=HiraiM en-aut-sei=Hirai en-aut-mei=M kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=MuraokaY en-aut-sei=Muraoka en-aut-mei=Y kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=YokoyaT en-aut-sei=Yokoya en-aut-mei=T kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= affil-num=1 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=3 en-affil= kn-affil=Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 affil-num=4 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=5 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=6 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=7 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=8 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=9 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=10 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=11 en-affil= kn-affil=Institute for Innovative Science and Technology, Graduate School of Engineering, Nagasaki Institute of Applied Science affil-num=12 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=13 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University affil-num=14 en-affil= kn-affil=The Graduate School of Natural Science and Technology, Okayama University END start-ver=1.4 cd-journal=joma no-vol=413 cd-vols= no-issue=4-6 article-no= start-page=379 end-page=383 dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20050926 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fabrication of a logic gate circuit based on ambipolar field-effect transistors with thin films of C60 and pentacene en-subtitle= kn-subtitle= en-abstract= kn-abstract=

Ambipolar field-effect transistor (FET) devices were fabricated with a heterostructure of C60 and pentacene, and their p- and n-channel field-effect mobilities were studied as a function of thickness of pentacene thin-films. The observed dependences of the values were interpreted in terms of the morphology of the thin films and the band structure of C60/pentacene heterostructure. A complementary metal-oxide-semiconductor (CMOS) circuit was fabricated by integration of two ambipolar FETs, aiming at realization of a new CMOS inverter circuit composed of FETs with the same device structure. The gain of 4, the threshold voltage of 85 V, and the complex output characteristics were explained on the basis of the properties of the component FET devices.

en-copyright= kn-copyright= en-aut-name=KuwaharaEiji en-aut-sei=Kuwahara en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KusaiHaruka en-aut-sei=Kusai en-aut-mei=Haruka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NaganoTakayuki en-aut-sei=Nagano en-aut-mei=Takayuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TakayanagiToshio en-aut-sei=Takayanagi en-aut-mei=Toshio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=3 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=4 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=5 en-affil= kn-affil=Department of Chemistry, Okayama University en-keyword=Band structure kn-keyword=Band structure en-keyword=Carbon kn-keyword=Carbon en-keyword=CMOS integrated circuits kn-keyword=CMOS integrated circuits en-keyword=Field effect transistors kn-keyword=Field effect transistors en-keyword=Logic gates kn-keyword=Logic gates en-keyword=Thin films kn-keyword=Thin films en-keyword=Threshold voltage kn-keyword=Threshold voltage en-keyword=Band structures kn-keyword=Band structures en-keyword=Logic gate circuits kn-keyword=Logic gate circuits en-keyword=N-channel field-effective mobilities kn-keyword=N-channel field-effective mobilities en-keyword=Pentacene kn-keyword=Pentacene en-keyword=Logic circuits kn-keyword=Logic circuits END start-ver=1.4 cd-journal=joma no-vol=71 cd-vols= no-issue=22 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20056 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Metallic phase in the metal-intercalated higher fullerene Rb8.8(7)C84 en-subtitle= kn-subtitle= en-abstract= kn-abstract=

A new material of higher fullerene, RbxC84, was synthesized by intercalating Rb metal into C-84 crystals. The RbxC(84) crystals showed a simple cubic (sc) structure with lattice constant, a, of 16.82 (2) angstrom at 6.5 K, and 16.87 (2) angstrom at 295 K. The Rietveld refinements were achieved with the space group, Pa (3) over bar, based on a model that the C-2 axis of D2d-C84 aligned along [111]. The sample composition was determined to be Rb-8.8(7) C-84. The ESR spectrum at 303 K was composed of a broad peak with peak-to-peak linewidth Delta H-pp of 220 G, and a narrow peak with Delta H-pp of 24 G. Temperature dependence of the broad peak clearly showed a metallic behavior. The metallic behavior was discussed based on a theoretical calculation. This finding of new metallic phase in a higher fullerene is the first step for a development of new types of fullerene materials with novel physical properties such as superconductivity.

en-copyright= kn-copyright= en-aut-name=RikiishiYoshie en-aut-sei=Rikiishi en-aut-mei=Yoshie kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KashinoYoko en-aut-sei=Kashino en-aut-mei=Yoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KusaiHaruka en-aut-sei=Kusai en-aut-mei=Haruka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TakabayashiYasuhiro en-aut-sei=Takabayashi en-aut-mei=Yasuhiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KuwaharaEiji en-aut-sei=Kuwahara en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KambeTakashi en-aut-sei=Kambe en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=TakenobuTaishi en-aut-sei=Takenobu en-aut-mei=Taishi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=IwasaYoshihiro en-aut-sei=Iwasa en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=MizorogiNaomi en-aut-sei=Mizorogi en-aut-mei=Naomi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=NagaseShigeru en-aut-sei=Nagase en-aut-mei=Shigeru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=OkadaSusumu en-aut-sei=Okada en-aut-mei=Susumu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=3 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=4 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=5 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=6 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=7 en-affil= kn-affil=Department of Physics, Okayama University affil-num=8 en-affil= kn-affil=CREST, Japan Science and Technology Agency affil-num=9 en-affil= kn-affil=CREST, Japan Science and Technology Agency affil-num=10 en-affil= kn-affil=Institute for Molecular Science affil-num=11 en-affil= kn-affil=Institute for Molecular Science affil-num=12 en-affil= kn-affil=Institute of Physics and Center for Computational Science, University of Tsukuba END start-ver=1.4 cd-journal=joma no-vol=89 cd-vols= no-issue=8 article-no= start-page=083511-1 end-page=083511-3 dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20068 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Output properties of C60 field-effect transistor device with Eu source/drain electrodes en-subtitle= kn-subtitle= en-abstract= kn-abstract=

Field-effect transistor (FET) device with thin films of C60 has been fabricated with Eu electrodes exhibiting small work function. The C60 FET device shows n-channel FET properties with high field-effect mobility, 0.50 cm2 V?1 s?1. Furthermore, nonvanishing drain current, i.e., normally on, is observed in this FET device. This originates from small energy barrier for electron from Eu source electrode to lowest unoccupied molecular orbital of C60.

en-copyright= kn-copyright= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=OchiKenji en-aut-sei=Ochi en-aut-mei=Kenji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NaganoTakayuki en-aut-sei=Nagano en-aut-mei=Takayuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OhtaToshio en-aut-sei=Ohta en-aut-mei=Toshio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=NouchiRyo en-aut-sei=Nouchi en-aut-mei=Ryo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MatsuokaYukitaka en-aut-sei=Matsuoka en-aut-mei=Yukitaka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=ShikohEiji en-aut-sei=Shikoh en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University affil-num=5 en-affil= kn-affil=Okayama University affil-num=6 en-affil= kn-affil=Japan Institute of Science and Technology affil-num=7 en-affil= kn-affil=Japan Institute of Science and Technology affil-num=8 en-affil= kn-affil=Japan Institute of Science and Technology en-keyword=device physics kn-keyword=device physics en-keyword=C60 kn-keyword=C60 en-keyword=Eu electrodes kn-keyword=Eu electrodes END start-ver=1.4 cd-journal=joma no-vol=87 cd-vols= no-issue=2 article-no= start-page=023501 end-page=023501 dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20057 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fabrication of field-effect transistor device with higher fullerene, C88 en-subtitle= kn-subtitle= en-abstract= kn-abstract=

A fullerene field-effect transistor (FET) device has been fabricated with thin films of C88, and n-channel normally-on depletion-type FET properties have been found in this FET device. The C88 FET exhibited a high mobility, μ, of 2.5 x 10-3 cm2 V-1 s-1 at 300 K, in fullerene FETs. The carrier transport showed a thermally-activated hopping transport. The n-channel normally-on FET properties and the hopping transport reflect the small mobility gap and low carrier concentration in the channel region of C88 thin-films.

en-copyright= kn-copyright= en-aut-name=NaganoTakayuki en-aut-sei=Nagano en-aut-mei=Takayuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SugiyamaHiroyuki en-aut-sei=Sugiyama en-aut-mei=Hiroyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KuwaharaEiji en-aut-sei=Kuwahara en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=WatanabeRie en-aut-sei=Watanabe en-aut-mei=Rie kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KusaiHaruka en-aut-sei=Kusai en-aut-mei=Haruka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=KashinoYoko en-aut-sei=Kashino en-aut-mei=Yoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University affil-num=5 en-affil= kn-affil=Okayama University affil-num=6 en-affil= kn-affil=Okayama University affil-num=7 en-affil= kn-affil=Okayama University en-keyword=fullerene devices kn-keyword=fullerene devices en-keyword=field effect transistors kn-keyword=field effect transistors en-keyword=carrier density kn-keyword=carrier density en-keyword=carrier mobility kn-keyword=carrier mobility en-keyword=hopping conduction kn-keyword=hopping conduction END start-ver=1.4 cd-journal=joma no-vol=87 cd-vols= no-issue=14 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=200510 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fabrication of C60 field-effect transistors with polyimide and Ba0.4Sr0.6Ti0.96O3 gate insulators en-subtitle= kn-subtitle= en-abstract= kn-abstract=

Flexible C60 field-effect transistor (FET) device has been fabricated with polyimide gate insulator on the poly(ethylene terephthalate) substrate, and n-channel normally-off FET properties are observed in this FET device. The field-effect mobility, ?, is estimated to be ~10-2 cm2 V-1 s-1 at 300 K. Furthermore, the C60 FET has been fabricated with high dielectric Ba0.4Sr0.6Ti0.96O3 (BST) gate insulator, showing n-channel properties; the ? value is estimated to be ~10-4 cm2 V-1 s-1 at 300 K. The FET device operates at very low gate voltage, VG, and low drain-source voltage, VDS. Thus these C60 FET devices possess flexibility and low-voltage operation characteristic of polyimide and BST gate insulators, respectively.

en-copyright= kn-copyright= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=NaganoTakayuki en-aut-sei=Nagano en-aut-mei=Takayuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HaruyamaYusuke en-aut-sei=Haruyama en-aut-mei=Yusuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KuwaharaEiji en-aut-sei=Kuwahara en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=TakayanagiToshio en-aut-sei=Takayanagi en-aut-mei=Toshio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=OchiKenji en-aut-sei=Ochi en-aut-mei=Kenji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil= kn-affil=Okayama University affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University affil-num=5 en-affil= kn-affil=Okayama University affil-num=6 en-affil= kn-affil=Okayama University affil-num=7 en-affil= kn-affil=Japan Advanced Institute of Science and Technology en-keyword=fullerene devices kn-keyword=fullerene devices en-keyword=insulated gate field effect transistors kn-keyword=insulated gate field effect transistors en-keyword=polymers kn-keyword=polymers en-keyword=barium compounds kn-keyword=barium compounds en-keyword=strontium compounds kn-keyword=strontium compounds en-keyword=dielectric materials kn-keyword=dielectric materials END start-ver=1.4 cd-journal=joma no-vol=69 cd-vols= no-issue=4 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2003 dt-pub=20037 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Scanning tunneling microscopy of Dy@C82 and Dy@C60 adsorbed on Si(111)-(7x7) surfaces en-subtitle= kn-subtitle= en-abstract= kn-abstract=

Dy@C-82 and Dy@C-60 adsorbed on Si(111)-(7x7) surface are investigated by scanning tunneling microscopy (STM) at 295 K. The Dy@C-82 molecules in the first layer are adsorbed on the Si(111)-(7x7) surface without formation of islands and nucleation, and the internal structure of the Dy@C-82 molecule is first observed on the surface at 295 K. The average heights of the Dy@C-82 molecules in the first and second layers are estimated to be 7.2 and 10.8 A, respectively, by STM. These results suggest strong interactions between the Si atoms and the Dy@C-82 molecules in the first layer. The STM image reveals that the Dy@C-60 molecule is nearly spherical, showing that the metal endohedral C-60 possesses a cage-form structure.

en-copyright= kn-copyright= en-aut-name=FujikiSatoshi en-aut-sei=Fujiki en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HosokawaTomoko en-aut-sei=Hosokawa en-aut-mei=Tomoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KanbaraTakayoshi en-aut-sei=Kanbara en-aut-mei=Takayoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=NonogakiYouichi en-aut-sei=Nonogaki en-aut-mei=Youichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=UrisuTsuneo en-aut-sei=Urisu en-aut-mei=Tsuneo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil= kn-affil=Graduate University for Advanced Studies affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Tohoku University affil-num=5 en-affil= kn-affil=Japan Advanced Institute of Science and Technology affil-num=6 en-affil= kn-affil=Institute for Molecular Science affil-num=7 en-affil= kn-affil=Graduate University for Advanced Studies en-keyword=endohedral metallofullerenes kn-keyword=endohedral metallofullerenes en-keyword=electronic-properties kn-keyword=electronic-properties en-keyword=c-60 kn-keyword=c-60 END start-ver=1.4 cd-journal=joma no-vol=70 cd-vols= no-issue=23 article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=1997 dt-pub=19972 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Scanning tunneling microscopy/spectroscopy studies of two isomers of Ce@C82 on Si(111)-(7~7）surfaces en-subtitle= kn-subtitle= en-abstract= kn-abstract=

Scanning tunneling microscopy images for two isomers of Ce@C-82 were observed on Si(111)-(7x7) at 295 K. The Ce@C-82 molecules in the first layer were bound to the Si surfaces, and the motions were frozen even at 295 K. The multilayer of the Ce@C-82 isomer I (Ce@C-82-I) produced a close-packed structure in the surface layer by annealing the Si substrate at 473 K. The distance between the nearest-neighboring molecules was 1.15(4) nm whose value was consistent with that, 1.12 nm, estimated from x-ray diffraction of the Ce@C-82-I crystals. This implies that the close-packed structure is dominated by van der Waals forces, as in crystals of Ce@C-82-I. The internal structure of Ce@C-82-I was observed in the first layer due to a freeze of molecular motion caused by strong interactions between the molecule and the Si adatoms in the surface. Scanning tunneling spectroscopy revealed that the energy gaps for Ce@C-82-I and -II in the first layer opened to gap energies, E-g of 0.7 and 1.0 eV, respectively. This fact suggests that these molecules are semiconductors with smaller value of E-g than those for C-60 and C-70.

en-copyright= kn-copyright= en-aut-name=FujikiSatoshi en-aut-sei=Fujiki en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=RikiishiYoshie en-aut-sei=Rikiishi en-aut-mei=Yoshie kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=UrisuTsuneo en-aut-sei=Urisu en-aut-mei=Tsuneo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil= kn-affil=Graduate University for Advanced Studies affil-num=2 en-affil= kn-affil=Science and Technology Agency affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Graduate University for Advanced Studies en-keyword=electronic-structure kn-keyword=electronic-structure en-keyword=endohedral metallofullerenes kn-keyword=endohedral metallofullerenes en-keyword=microscopy kn-keyword=microscopy en-keyword=lanthanum kn-keyword=lanthanum en-keyword=crystal kn-keyword=crystal en-keyword=anion kn-keyword=anion en-keyword=films kn-keyword=films END start-ver=1.4 cd-journal=joma no-vol=409 cd-vols= no-issue=4-6 article-no= start-page=187 end-page=191 dt-received= dt-revised= dt-accepted= dt-pub-year=2005 dt-pub=20050630 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fabrication and characterization of field-effect transistor device with C2v isomer of Pr@C82 en-subtitle= kn-subtitle= en-abstract= kn-abstract=

A field-effect transistor (FET) device was fabricated with thin films of C2v isomer of Pr@C82. This device apparently showed n-channel normally-on type FET properties, where non-zero current was observed at gate-source voltage of 0 VGS, of 0V. Normally off FET properties were observed by subtraction of the non-zero current from the drain current.Thus the normally on properties are ascribed to the high bulk current caused by the small energy gap ?0.3 eV. The field-effect mobility for this FET was 1.5 x 10-4 cm2 V-1 s-1 at 320 K, being comparable to those of other endohedral metallofullerene FET devices.

en-copyright= kn-copyright= en-aut-name=NaganoTakayuki en-aut-sei=Nagano en-aut-mei=Takayuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KuwaharaEiji en-aut-sei=Kuwahara en-aut-mei=Eiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakayanagiToshio en-aut-sei=Takayanagi en-aut-mei=Toshio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=3 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=4 en-affil= kn-affil=Department of Chemistry, Okayama University affil-num=5 en-affil= kn-affil=CREST, Japan Science and Technology Agency en-keyword=Field effect transistors kn-keyword=Field effect transistors END