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=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=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=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