Yoshihiro Kubozono

Correction: Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes

Co-reporter:Yoshihiro Kubozono, Keita Hyodo, Hiroki Mori, Shino Hamao, Hidenori Goto and Yasushi Nishihara

Journal of Materials Chemistry A 2015 vol. 3(Issue 12) pp:2960-2960

Publication Date(Web):25 Feb 2015

DOI:10.1039/C5TC90044A

Correction for ‘Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes’ by Yoshihiro Kubozono et al., J. Mater. Chem. C, 2015, 3, DOI: 10.1039/c4tc02413c.

Transistors fabricated using the single crystals of [8]phenacene

Co-reporter:Yuma Shimo, Takahiro Mikami, Hiroto T. Murakami, Shino Hamao, Hidenori Goto, Hideki Okamoto, Shin Gohda, Kaori Sato, Antonio Cassinese, Yasuhiko Hayashi and Yoshihiro Kubozono

Journal of Materials Chemistry A 2015 vol. 3(Issue 28) pp:7370-7378

Publication Date(Web):24 Jun 2015

DOI:10.1039/C5TC00960J

Field-effect transistors (FETs) with single crystals of a new phenacene-type molecule, [8]phenacene, were fabricated and characterized. This new molecule consists of a phenacene core of eight benzene rings, with an extended π-conjugated system, which was recently synthesized for use in an FET by our group. The FET characteristics of an [8]phenacene single-crystal FET with SiO2 gate dielectrics show typical p-channel properties with an average field-effect mobility, 〈μ〉, as high as 3(2) cm2 V−1 s−1 in two-terminal measurement mode, which is a relatively high value for a p-channel single-crystal FET. The 〈μ〉 was determined to be 6(2) cm2 V−1 s−1 in four-terminal measurement mode. Low-voltage operation was achieved with PbZr0.52Ti0.48O3 (PZT) as the gate dielectric, and an electric-double-layer (EDL) capacitor. The 〈μ〉 and average values of absolute threshold voltage, 〈|Vth|〉, were 1.6(4) cm2 V−1 s−1 and 5(1) V, respectively, for PZT, and 4(2) × 10−1 cm2 V−1 s−1 and 2.38(4) V, respectively, for the EDL capacitor; these values were evaluated in two-terminal measurement mode. The inverter circuit was fabricated using [8]phenacene and N,N′-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide single-crystal FETs. This is the first logic gate circuit using phenacene molecules. Furthermore, the relationship between μ and the number of benzene rings was clarified based on this study and the previous studies on phenacene single-crystal FETs.

Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes

Co-reporter:Yoshihiro Kubozono, Keita Hyodo, Hiroki Mori, Shino Hamao, Hidenori Goto and Yasushi Nishihara

Journal of Materials Chemistry A 2015 vol. 3(Issue 10) pp:2413-2421

Publication Date(Web):19 Jan 2015

DOI:10.1039/C4TC02413C

Field-effect transistors (FETs) have been fabricated with thin films of a series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene derivatives (Cn-PDTs). The FET characteristics of Cn-PDT thin-film FETs with an SiO2 gate dielectric as well as high-k gate dielectrics were recorded, and the dependence of the field-effect mobility, μ, on the number (n) of carbon atoms in the alkyl chains was investigated, showing that the 2,9-didodecylphenanthro[1,2-b:8,7-b′]dithiophene (C12-PDT) thin-film FET displays superior properties, with μs as high as 1.8 cm2 V−1 s−1 for the SiO2 gate dielectric and 2.2 cm2 V−1 s−1 for the HfO2 gate dielectric. The average μ values, 〈μ〉, reach 1.1(5) and 1.8(6) cm2 V−1 s−1, respectively, for the SiO2 and ZrO2 gate dielectrics. Low-voltage operation, showing an absolute average threshold voltage 〈|Vth|〉 of ∼11 V, was implemented, together with the above high 〈μ〉 of ∼2 cm2 V−1 s−1. Also, a flexible FET was fabricated with a parylene gate dielectric. The results of this study show the potential of the C12-PDT molecule for application in a high-performance transistor.

1D and 2D Bi Compounds in Field-Effect Transistors

Co-reporter:Eri Uesugi;Saki Nishiyama;Hidehiko Akiyoshi;Hidenori Goto;Yoji Koike;Kazuyoshi Yamada

Advanced Electronic Materials 2015 Volume 1( Issue 8) pp:

Publication Date(Web):

DOI:10.1002/aelm.201500085

Transistor Application of Phenacene Molecules and Their Characteristics (Eur. J. Inorg. Chem. 24/2014)

Co-reporter:Yoshihiro Kubozono;Xuexia He;Shino Hamao;Kazuya Teranishi;Hidenori Goto;Ritsuko Eguchi;Takashi Kambe;Shin Gohda;Yasushi Nishihara

European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 24) pp:

Publication Date(Web):

DOI:10.1002/ejic.201490121

Transistor Application of Phenacene Molecules and Their Characteristics

Co-reporter:Yoshihiro Kubozono;Xuexia He;Shino Hamao;Kazuya Teranishi;Hidenori Goto;Ritsuko Eguchi;Takashi Kambe;Shin Gohda;Yasushi Nishihara

European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 24) pp:3806-3819

Publication Date(Web):

DOI:10.1002/ejic.201402168

Abstract

The characteristics of field-effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this review together with the electronic and crystal structures of phenacenes. Phenacene molecules possess a low HOMO level and a wide band gap. The highest mobility observed in the phenacene thin-film FETs is 7.4 cm² V^–1 s^–1 for [6]phenacene, and in single-crystal FETs the highest value is 6.3 cm² V^–1 s^–1 for [7]phenacene. The phenacene thin-film FETs show O₂-sensing properties unlike their single-crystal FETs. The bias-stress effect is fully investigated for phenacene single-crystal FETs. Furthermore, the low-voltage operation of phenacene single-crystal FETs with electric-double-layer (EDL) capacitors is reported. The temperature dependence of phenacene single-crystal FETs is reported to clarify the transport mechanism, which is suggestive of band-like transport.

Systematic Control of Hole-Injection Barrier Height with Electron Acceptors in [7]phenacene Single-Crystal Field-Effect Transistors

Co-reporter:Xuexia He ; Shino Hamao ; Ritsuko Eguchi ; Hidenori Goto ; Yukihiro Yoshida ; Gunzi Saito

The Journal of Physical Chemistry C 2014 Volume 118(Issue 10) pp:5284-5293

Publication Date(Web):February 14, 2014

DOI:10.1021/jp4107469

The interface between the single crystal and the Au source/drain electrodes in [7]phenacene single-crystal field-effect transistors (FETs) was modified using 14 electron acceptors with different redox potentials. The effective hole-injection barrier heights (ϕheffs) for [7]phenacene single-crystal FETs have been plotted as a function of the redox potential (Eredox) of the inserted electron acceptors, showing that the ϕheff decreases with increasing Eredox. The highest ϕheff occurs without inserted material (electron acceptors), and this deviates from the otherwise linear relationship between ϕheff and Eredox. We have investigated the temperature dependence of ϕheff in an attempt to determine why the ϕheff value without inserted material is so high, which suggests that no additional barrier, such as a tunneling barrier, is formed in the device. We conclude that the pure Schottky barrier in this FET is lowered very significantly by the insertion of an electron acceptor. The gate-voltage dependence of ϕheff suggests a slight reduction of Schottky barrier height owing to hole accumulation. Furthermore, the clear correlation between threshold voltage and redox potential suggests a relationship between threshold voltage and ϕheff. Controlling the interface between the single crystal and the source/drain electrodes in this FET produced a very high μ (∼6.9 cm2 V–1 s–1) and low absolute threshold voltage, i.e., excellent FET characteristics. The topological characterization of inserted materials on [7]phenacene single crystals are achieved using atomic force microscope (AFM) and X-ray diffraction (XRD). The results show that the single crystals are not completely covered with the inserted materials and the inhomogeneous modification of inserted materials for single crystals effectively leads to the drastic change of hole-injection barrier between source/drain electrodes and single-crystal active layer.

Fabrication of single crystal field-effect transistors with phenacene-type molecules and their excellent transistor characteristics

Co-reporter:Xuexia He, Ritsuko Eguchi, Hidenori Goto, Eri Uesugi, Shino Hamao, Yasuhiro Takabayashi, Yoshihiro Kubozono

Organic Electronics 2013 Volume 14(Issue 6) pp:1673-1682

Publication Date(Web):June 2013

DOI:10.1016/j.orgel.2013.03.035

•Fabrication of field-effect transistors with single crystals of new phenacene molecules.•Achievement of high field-effect mobility and low voltage operation in single crystal field-effect transistors.•Interface modification with electron-acceptor molecules to improve the transistor performance.Single crystal field-effect transistors (FETs) using [6]phenacene and [7]phenacene show p-channel FET characteristics. Field-effect mobilities, μs, as high as 5.6 × 10−1 cm2 V−1 s−1 in a [6]phenacene single crystal FET with an SiO2 gate dielectric and 2.3 cm2 V−1 s−1 in a [7]phenacene single crystal FET were recorded. In these FETs, 7,7,8,8-tetracyanoquinodimethane (TCNQ) was inserted between the Au source/drain electrodes and the single crystal to reduce hole-injection barrier heights. The μ reached 3.2 cm2 V−1 s−1 in the [7]phenacene single crystal FET with a Ta2O5 gate dielectric, and a low absolute threshold voltage |VTH| (6.3 V) was observed. Insertion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the interface produced very a high μ value (4.7–6.7 cm2 V−1 s−1) in the [7]phenacene single crystal FET, indicating that F4TCNQ was better for interface modification than TCNQ. A single crystal electric double-layer FET provided μ as high as 3.8 × 10−1 cm2 V−1 s−1 and |VTH| as low as 2.3 V. These results indicate that [6]phenacene and [7]phenacene are promising materials for future practical FET devices, and in addition we suggest that such devices might also provide a research tool to investigate a material’s potential as a superconductor and a possible new way to produce the superconducting state.Graphical abstract

Phenanthro[1,2-b:8,7-b’]dithiophene: a new picene-type molecule for transistor applications

Co-reporter:Yasushi Nishihara, Megumi Kinoshita, Keita Hyodo, Yasuhiro Okuda, Ritsuko Eguchi, Hidenori Goto, Shino Hamao, Yasuhiro Takabayashi and Yoshihiro Kubozono

RSC Advances 2013 vol. 3(Issue 42) pp:19341-19347

Publication Date(Web):12 Aug 2013

DOI:10.1039/C3RA44050H

A new picene-type molecule, phenanthro[1,2-b:8,7-b’]dithiophene, has been synthesized for use in organic field-effect transistors (OFETs). The molecule consists of a phenanthrene core with two thiophene rings fused on the ends. This molecule can be recognized as a picene analogue. The electronic structure of the molecule was determined by its optical absorption spectrum together with a theoretical calculation based on density functional theory (DFT). The topological and electronic structures of thin films produced by direct thermal evaporation of the compounds and by deposition from a solution were characterized by optical imaging, X-ray diffraction, and atomic force microscopy. FET devices were fabricated with these thin films, and showed field-effect mobility as high as 10−1 cm2 V−1 s−1.

O2-exposure and light-irradiation properties of picene thin film field-effect transistor: A new way toward O2 gas sensor

Co-reporter:Yasuyuki Sugawara, Keiko Ogawa, Hidenori Goto, Shuhei Oikawa, Kouki Akaike, Noriko Komura, Ritsuko Eguchi, Yumiko Kaji, Shin Gohda, Yoshihiro Kubozono

Sensors and Actuators B: Chemical 2012 s 171–172() pp: 544-549

Publication Date(Web):

DOI:10.1016/j.snb.2012.05.030

Characteristics of Single Crystal Field-Effect Transistors with a New Type of Aromatic Hydrocarbon, Picene

Co-reporter:Nobuyuki Kawai, Ritsuko Eguchi, Hidenori Goto, Kouki Akaike, Yumiko Kaji, Takashi Kambe, Akihiko Fujiwara, and Yoshihiro Kubozono

The Journal of Physical Chemistry C 2012 Volume 116(Issue 14) pp:7983-7988

Publication Date(Web):March 21, 2012

DOI:10.1021/jp300052p

Picene is a phenacene-type aromatic hydrocarbon molecule with five benzene rings. We have fabricated picene single crystal (SC) field-effect transistors (FETs) with solid gate and ionic liquid gate dielectrics. Although the picene SC FET showed a large hole-injection barrier without any modification of interface between source/drain electrodes and picene SC, such a large hole-injection barrier could be effectively reduced by modifying the interface with tetracyanoquinodimethane (TCNQ). Picene SC FET with an HfO2 gate dielectric and TCNQ-coated electrodes shows p-channel characteristics with a smooth hole injection and a field-effect mobility more than 1 cm2 V–1 s–1 in two-terminal measurement. Picene SC FET could be operated even in bottom-contact structure by modifying the interface with octanethiol. Furthermore, picene SC FET operated with ionic liquid gate dielectric, [1-butyl-3-methylimidazolium][hexafluorophosphate], showing the field-effect mobility of 1.8 × 10–1 cm2 V–1 s–1 and low absolute value, 1.9 V, of threshold voltage.

Metal-intercalated aromatic hydrocarbons: a new class of carbon-based superconductors

Co-reporter:Yoshihiro Kubozono, Hiroki Mitamura, Xuesong Lee, Xuexia He, Yusuke Yamanari, Yosuke Takahashi, Yuta Suzuki, Yumiko Kaji, Ritsuko Eguchi, Koki Akaike, Takashi Kambe, Hideki Okamoto, Akihiko Fujiwara, Takashi Kato, Taichi Kosugi and Hideo Aoki

Physical Chemistry Chemical Physics 2011 vol. 13(Issue 37) pp:16476-16493

Publication Date(Web):17 Aug 2011

DOI:10.1039/C1CP20961B

New carbon-based superconductors are synthesized by intercalating metal atoms into the solid-phase hydrocarbons picene and coronene. The highest reported superconducting transition temperature, Tc, of a hydrocarbon superconductor is 18 K for K3picene. The physics and chemistry of the hydrocarbon superconductors are extensively described for Axpicene (A: alkali and alkali earth-metal atoms) for x = 0–5. The theoretical picture of their electronic structure is also reviewed. Future prospects for hydrocarbon superconductors are discussed from the viewpoint of combining electronics with condensed-matter physics: modification of the physical properties of hydrocarbon solids is explored by building them into a field-effect transistor. The features of other carbon-based superconductors are compared to clarify the nature of hydrocarbon superconductors.

Characteristics of conjugated hydrocarbon based thin film transistor with ionic liquid gate dielectric

Co-reporter:Yumiko Kaji, Keiko Ogawa, Ritsuko Eguchi, Hidenori Goto, Yasuyuki Sugawara, Takashi Kambe, Koki Akaike, Shin Gohda, Akihiko Fujiwara, Yoshihiro Kubozono

Organic Electronics 2011 Volume 12(Issue 12) pp:2076-2083

Publication Date(Web):December 2011

DOI:10.1016/j.orgel.2011.08.016

Thin film transistors (TFTs) with ionic liquid gate dielectrics, [1-ethyl-3-methylimidazolium][bis(trifluoromethanesulfonyl)imide] (emim[TFSI]) and [1-butyl-3-methylimidazolium][hexafluorophosphate] (bmim[PF6]), are fabricated with thin films of one dimensional (1D) hydrocarbon, [7]phenacene. P-channel characteristics are observed for [7]phenacene TFTs with both ionic liquids by use of platinum electrode. The field-effect mobility μ for [7]phenacene TFT with bmim[PF6] was recorded to be 0.28 cm2 V−1 s−1. The value of absolute threshold voltage, |VTH|, was less than 2.5 V, showing low-voltage operation. The accumulation of hole in the [7]phenacene TFTs with ionic liquids was confirmed from the voltage or time dependence of capacitance in metal–insulator-semiconductor structure, which shows that these TFTs operate electrochemically and the carriers are accumulated in the whole of [7]phenacene thin films.Graphical abstractHighlights► We made aromatic hydrocarbon ([7]phenacene) electrochemical transistor with ionic liquids. ► Low voltage operation and high field-effect mobility was realized in [7]phenacene electrochemical transistor. ► Availability of bmim[PF6] gel for electrochemical transitor was shown. ► Future prospective is shown for application of aromatic hydrocarbon electrochemical transistor.

Anomalous hysteresis in organic field-effect transistors with SAM-modified electrodes: Structural switching of SAMs by electric field

Co-reporter:Ryo Nouchi, Yoshihiro Kubozono

Organic Electronics 2010 Volume 11(Issue 6) pp:1025-1030

Publication Date(Web):June 2010

DOI:10.1016/j.orgel.2010.02.017

Self-assembled monolayers (SAMs) are efficient tuners of metal work functions, and have been widely used to modify source/drain electrodes of organic field-effect transistors (OFETs) to achieve effective charge injection from the electrodes into organic semiconducting layers. The device characteristics of OFETs with Au electrodes modified with 1-alkanethiol SAMs were investigated and displayed an anomalous hysteresis opposite to that generally observed. Measurements of OFETs with different SAM molecular species or different average surface densities indicate that an increase in drain currents by tunneling-barrier narrowing accompanied by a structural order–disorder switching of the SAMs causes such hysteretic behavior. Furthermore, time evolution measurements of OFET drain currents indicate that an electric field perpendicular to the surface of the SAM-modified electrodes, i.e., a drain voltage, induces the switching. The anomalous hysteresis unveiled in this study is indicative of an electrically-stimulated switching of SAMs, which has many implications with respect to the development of future molecular switches.

Quantitative analysis of O2 gas sensing characteristics of picene thin film field-effect transistors

Co-reporter:Xuesong Lee, Yasuyuki Sugawara, Akio Ito, Shuhei Oikawa, Naoko Kawasaki, Yumiko Kaji, Ryoji Mitsuhashi, Hideki Okamoto, Akihiko Fujiwara, Kenji Omote, Takashi Kambe, Naoshi Ikeda, Yoshihiro Kubozono

Organic Electronics 2010 Volume 11(Issue 8) pp:1394-1398

Publication Date(Web):August 2010

DOI:10.1016/j.orgel.2010.06.003

O2 gas sensing behaviors are studied in picene thin film field-effect transistors (FETs) with hydrophobic polymer (Cytop™ or polystyrene) coated SiO2 gate dielectrics. Picene thin film FETs show a rapid reduction of hysteresis in transfer curves recorded in forward and reverse measurement modes, compared to a picene FET with hexamethydisilazane-coated SiO2. The picene FETs show very sensitive O2 gas sensing effects down to ∼10 ppm. A quantitative analysis is presented of the gate voltage (VG) dependent mobility induced by O2 exposure, i.e., the suppression of drain current at high VG.

Superconductivity in alkali-metal-doped picene

Co-reporter:Ryoji Mitsuhashi, Yuta Suzuki, Yusuke Yamanari, Hiroki Mitamura, Takashi Kambe, Naoshi Ikeda, Hideki Okamoto, Akihiko Fujiwara, Minoru Yamaji, Naoko Kawasaki, Yutaka Maniwa & Yoshihiro Kubozono

Nature 2010 464(7285) pp:76

Publication Date(Web):2010-03-04

DOI:10.1038/nature08859

The phenomenon of superconductivity continues to intrigue, and several new superconducting materials have been discovered in recent years — but in the case of organic superconductors, no new material system with a high superconducting transition temperature has been identified in the past decade. Now it has been shown that the introduction of potassium into crystals of organic molecule picene can yield superconductivity at temperatures as high as 18 K.

High-performance C60 and picene thin film field-effect transistors with conducting polymer electrodes in bottom contact structure

Co-reporter:Yumiko Kaji, Ryoji Mitsuhashi, Xuesong Lee, Hideki Okamoto, Takashi Kambe, Naoshi Ikeda, Akihiko Fujiwara, Minoru Yamaji, Kenji Omote, Yoshihiro Kubozono

Organic Electronics 2009 Volume 10(Issue 3) pp:432-436

Publication Date(Web):May 2009

DOI:10.1016/j.orgel.2009.01.006

Transport properties of field-effect transistors with thin films of C76 and its electronic structure

Co-reporter:Hiroyuki Sugiyama, Takayuki Nagano, Ryo Nouchi, Naoko Kawasaki, Yohei Ohta, Kumiko Imai, Michiko Tsutsui, Yoshihiro Kubozono, Akihiko Fujiwara

Chemical Physics Letters 2007 Volume 449(1–3) pp:160-164

Publication Date(Web):26 November 2007

DOI:10.1016/j.cplett.2007.10.012

Abstract

The C₇₆ field-effect transistor (FET) showed n-channel normally-off like behavior with n-channel field-effect mobility, μ_n, of 3.9 × 10⁻⁴ cm² V⁻¹ s⁻¹, and the highest on–off ratio, 125, among higher fullerenes FETs. The carrier transport in the C₇₆ FET followed a thermally-activated hopping transport model. The normally-off like properties of C₇₆ FET could be reasonably explained in terms of the electronic structure of thin films determined by photoemission spectroscopy.

Nanoscale patterning by manipulation of single C60 molecules with a scanning tunneling microscope

Co-reporter:Satoshi Fujiki, Kosuke Masunari, Ryo Nouchi, Hiroyuki Sugiyama, Yoshihiro Kubozono, Akihiko Fujiwara

Chemical Physics Letters 2006 Volume 420(1–3) pp:82-85

Publication Date(Web):10 March 2006

DOI:10.1016/j.cplett.2005.12.052

Abstract

We report a new technique for inscribing characters, pictures and patterns on a nanometer scale by pin-point shooting at single C₆₀ molecules. An exact and sharp electron/hole injection precisely removes a single target C₆₀ molecule in the close-packed C₆₀ layer. This leaves a small dark void on the scanning tunneling microscope image. Furthermore, a pin-point shooting at a C₆₀ molecule adjacent to a void can cause the molecule to slide and fill up the void. Such a movement of a single C₆₀ molecule provides a new way for precisely recording characters, pictures and patterns on a nanometer scale.

Fabrication and characterization of field-effect transistor device with C2v isomer of Pr@C82

Co-reporter:Takayuki Nagano, Eiji Kuwahara, Toshio Takayanagi, Yoshihiro Kubozono, Akihiko Fujiwara

Chemical Physics Letters 2005 Volume 409(4–6) pp:187-191

Publication Date(Web):30 June 2005

DOI:10.1016/j.cplett.2005.05.019

Abstract

A field-effect transistor (FET) device was fabricated with thin films of C_2v isomer of Pr@C₈₂. This device apparently showed n-channel normally on type FET properties, where non-zero current was observed at the gate–source voltage, V_GS, of 0 V. 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 of ≈0.3 eV. The field-effect mobility for this FET was 1.5 × 10⁻⁴ cm² V⁻¹ s⁻¹ at 320 K, being comparable to those of other endohedral metallofullerene FET devices.

Electronic properties for the C2v and Cs isomers of Pr@C82 studied by Raman, resistivity and scanning tunneling microscopy/spectroscopy

Co-reporter:Tomoko Hosokawa, Satoshi Fujiki, Eiji Kuwahara, Yoshihiro Kubozono, Hiroshi Kitagawa, Akihiko Fujiwara, Taishi Takenobu, Yoshihiro Iwasa

Chemical Physics Letters 2004 Volume 395(1–3) pp:78-81

Publication Date(Web):1 September 2004

DOI:10.1016/j.cplett.2004.07.072

Abstract

Electronic properties of the major and minor isomers of Pr@C₈₂, I (C_2v) and II (C_s), are studied by Raman scattering, resistivity measurement, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). The valences of the Pr atom in both isomers are determined to be +3 based on the Raman shift in the Pr–C₈₂ stretching mode. The transport properties showed that both isomers are normal semiconductors with a small energy gap (E_g). STM of isomer I shows internal structures dependent on bias voltage V_s, and STS shows that this isomer is a semiconductor with E_g = 0.7 eV.

N-channel field effect transistors with fullerene thin films and their application to a logic gate circuit

Co-reporter:T. Kanbara, K. Shibata, S. Fujiki, Y. Kubozono, S. Kashino, T. Urisu, M. Sakai, A. Fujiwara, R. Kumashiro, K. Tanigaki

Chemical Physics Letters 2003 Volume 379(3–4) pp:223-229

Publication Date(Web):26 September 2003

DOI:10.1016/j.cplett.2003.07.025

N-channel field effect transistors (FETs) were fabricated with thin films of C60 and Dy@C82. A typical enhancement-type FET property was observed in C60 FET above 220 K. The mobility of C60 FET increased with increasing temperature. This fact suggests hopping transport as the conduction mechanism, with the activation energy of 0.29 eV. The Dy@C82 FET was found to be a normally-on type FET, which has a property different from that for C60 and C70 FETs. A complementary metal oxide semiconductor (CMOS) logic gate circuit was first fabricated with C60 and pentacene thin-film FETs.

Structure and electronic properties of Dy@C82 studied by UV–VIS absorption, X-ray powder diffraction and XAFS

Co-reporter:S. Iida, Y. Kubozono, Y. Slovokhotov, Y. Takabayashi, T. Kanbara, T. Fukunaga, S. Fujiki, S. Emura, S. Kashino

Chemical Physics Letters 2001 Volume 338(Issue 1) pp:21-28

Publication Date(Web):13 April 2001

DOI:10.1016/S0009-2614(01)00234-2

Abstract

Two isomers of Dy@C₈₂ were separated by high performance liquid chromatography (HPLC), and their UV–VIS absorption spectra were measured to characterize these isomers. The crystalline powder of Dy@C₈₂ was obtained by removing the solvent (toluene) at 250°C under vacuum. The X-ray diffraction pattern can be indexed with fcc crystal lattice, as that in La@C₈₂. The lattice constant a at 298 K, 15.86(1) Å, is close to that of La@C₈₂, 15.78 Å. The distances between Dy and the first and second nearest C atoms are determined to be 2.52(2) and 2.86(2) Å, respectively, on the basis of Dy L_III-edge EXAFS. The XANES shows that the valence of the Dy atom in Dy@C₈₂ is +3.

Structure of La2@C80 studied by La K-edge XAFS

Co-reporter:Y Kubozono, Y Takabayashi, S Kashino, M Kondo, T Wakahara, T Akasaka, K Kobayashi, S Nagase, S Emura, K Yamamoto

Chemical Physics Letters 2001 Volume 335(3–4) pp:163-169

Publication Date(Web):23 February 2001

DOI:10.1016/S0009-2614(01)00048-3

Abstract

The structure of La₂@C₈₀ is studied by La K-edge XAFS from 40 to 295 K. The distances between the La atom and the first nearest C atoms have been determined to be 2.42(1) Å at 40 K and 2.44(2) Å at 295 K, and those between the La atom and the second nearest C atoms to be 2.97(2) Å at 40 K and 2.98(3) Å at 295 K. The La–La distance has been determined to be 3.90(1) Å at 40 K and 3.88(2) Å at 295 K. The temperature dependence of the mean-square displacement of La–C is also studied to get an insight into the dynamical behavior of two La atoms in the C₈₀ cage.

Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes

Co-reporter:Yoshihiro Kubozono, Keita Hyodo, Hiroki Mori, Shino Hamao, Hidenori Goto and Yasushi Nishihara

Journal of Materials Chemistry A 2015 - vol. 3(Issue 10) pp:NaN2421-2421

Publication Date(Web):2015/01/19

DOI:10.1039/C4TC02413C

Field-effect transistors (FETs) have been fabricated with thin films of a series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene derivatives (Cn-PDTs). The FET characteristics of Cn-PDT thin-film FETs with an SiO2 gate dielectric as well as high-k gate dielectrics were recorded, and the dependence of the field-effect mobility, μ, on the number (n) of carbon atoms in the alkyl chains was investigated, showing that the 2,9-didodecylphenanthro[1,2-b:8,7-b′]dithiophene (C12-PDT) thin-film FET displays superior properties, with μs as high as 1.8 cm2 V−1 s−1 for the SiO2 gate dielectric and 2.2 cm2 V−1 s−1 for the HfO2 gate dielectric. The average μ values, 〈μ〉, reach 1.1(5) and 1.8(6) cm2 V−1 s−1, respectively, for the SiO2 and ZrO2 gate dielectrics. Low-voltage operation, showing an absolute average threshold voltage 〈|Vth|〉 of ∼11 V, was implemented, together with the above high 〈μ〉 of ∼2 cm2 V−1 s−1. Also, a flexible FET was fabricated with a parylene gate dielectric. The results of this study show the potential of the C12-PDT molecule for application in a high-performance transistor.

Correction: Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes

Co-reporter:Yoshihiro Kubozono, Keita Hyodo, Hiroki Mori, Shino Hamao, Hidenori Goto and Yasushi Nishihara

Journal of Materials Chemistry A 2015 - vol. 3(Issue 12) pp:NaN2960-2960

Publication Date(Web):2015/02/25

DOI:10.1039/C5TC90044A

Correction for ‘Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes’ by Yoshihiro Kubozono et al., J. Mater. Chem. C, 2015, 3, DOI: 10.1039/c4tc02413c.

Metal-intercalated aromatic hydrocarbons: a new class of carbon-based superconductors

Co-reporter:Yoshihiro Kubozono, Hiroki Mitamura, Xuesong Lee, Xuexia He, Yusuke Yamanari, Yosuke Takahashi, Yuta Suzuki, Yumiko Kaji, Ritsuko Eguchi, Koki Akaike, Takashi Kambe, Hideki Okamoto, Akihiko Fujiwara, Takashi Kato, Taichi Kosugi and Hideo Aoki

Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 37) pp:NaN16493-16493

Publication Date(Web):2011/08/17

DOI:10.1039/C1CP20961B

New carbon-based superconductors are synthesized by intercalating metal atoms into the solid-phase hydrocarbons picene and coronene. The highest reported superconducting transition temperature, Tc, of a hydrocarbon superconductor is 18 K for K3picene. The physics and chemistry of the hydrocarbon superconductors are extensively described for Axpicene (A: alkali and alkali earth-metal atoms) for x = 0–5. The theoretical picture of their electronic structure is also reviewed. Future prospects for hydrocarbon superconductors are discussed from the viewpoint of combining electronics with condensed-matter physics: modification of the physical properties of hydrocarbon solids is explored by building them into a field-effect transistor. The features of other carbon-based superconductors are compared to clarify the nature of hydrocarbon superconductors.

Transistors fabricated using the single crystals of [8]phenacene

Co-reporter:Yuma Shimo, Takahiro Mikami, Hiroto T. Murakami, Shino Hamao, Hidenori Goto, Hideki Okamoto, Shin Gohda, Kaori Sato, Antonio Cassinese, Yasuhiko Hayashi and Yoshihiro Kubozono

Journal of Materials Chemistry A 2015 - vol. 3(Issue 28) pp:NaN7378-7378

Publication Date(Web):2015/06/24

DOI:10.1039/C5TC00960J

Field-effect transistors (FETs) with single crystals of a new phenacene-type molecule, [8]phenacene, were fabricated and characterized. This new molecule consists of a phenacene core of eight benzene rings, with an extended π-conjugated system, which was recently synthesized for use in an FET by our group. The FET characteristics of an [8]phenacene single-crystal FET with SiO2 gate dielectrics show typical p-channel properties with an average field-effect mobility, 〈μ〉, as high as 3(2) cm2 V−1 s−1 in two-terminal measurement mode, which is a relatively high value for a p-channel single-crystal FET. The 〈μ〉 was determined to be 6(2) cm2 V−1 s−1 in four-terminal measurement mode. Low-voltage operation was achieved with PbZr0.52Ti0.48O3 (PZT) as the gate dielectric, and an electric-double-layer (EDL) capacitor. The 〈μ〉 and average values of absolute threshold voltage, 〈|Vth|〉, were 1.6(4) cm2 V−1 s−1 and 5(1) V, respectively, for PZT, and 4(2) × 10−1 cm2 V−1 s−1 and 2.38(4) V, respectively, for the EDL capacitor; these values were evaluated in two-terminal measurement mode. The inverter circuit was fabricated using [8]phenacene and N,N′-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide single-crystal FETs. This is the first logic gate circuit using phenacene molecules. Furthermore, the relationship between μ and the number of benzene rings was clarified based on this study and the previous studies on phenacene single-crystal FETs.