A gate-induced thermally stimulated current (TSC) on β′-(BEDT-TTF)(TCNQ) crystalline FET were conducted to elucidate the previously observed ferroelectric-like behaviors. TSC which is symmetric for the polarization of an applied V P G and has a peak at around 285 K was assigned as a pyroelectric current. By integrating the pyroelectric current, temperature dependence of the remnant polarization charge was obtained and the existence of the ferroelectric phase transition at 285 K was clearly demonstrated. We have tentatively concluded that the phase transition between dimer Mott insulator and charge ordered phase occurred at around the interface of organic crystal and substrate.
References
[1]
Yamamoto, K.; Kowalska, A.A.; Yakushi, K. Direct observation of ferroelectric domains created by Wigner crystallization of electrons in α-[bis(ethylenedithio)tetrathiafulvalene]2I3. Appl. Phys. Lett. 2010, 96 122901-1-122901-3., 122901–1, doi:10.1063/1.3327810.
[2]
Yamamoto, K.; Kowalska, A.A.; Nakano, C.; Yakushi, K. Inhomogeneous ferroelectric polarization in α '-(BEDT-TTF)2IBr2 revealed by second-harmonic generation microscopy. Physica B 2010, 405, S363–S364, doi:10.1016/j.physb.2009.10.027.
[3]
Kowalska, A.A.; Yamamoto, K.; Nakano, C.; Yakushi, K. Ferroelectric Polarization in α-(ET)2I2Br Studied by Second -Harmonic Generation Microscopy. J. Phys. 2008, 132 012006-1-012006-5, 012006–1.
[4]
Yamamoto, K.; Iwai, S.; Boyko, S.; Kashiwazaki, A.; Hiramatsu, F.; Okabe, C.; Nishi, N.; Yakushi, K. Strong Optical Nonlinearity and its Ultrafast Response Associated with Electron Ferroelectricity in an Organic Conductor. J. Phys. Soc. Jpn. 2008, 77 074709-1-074709-6., 074709–1, doi:10.1143/JPSJ.77.074709.
[5]
Abdel-Jawad, M.; Terasaki, I.; Sasaki, T.; Yoneyama, N.; Kobayashi, N.; Uesu, Y.; Hotta, C. Anomalous dielectric response in the dimer Mott insulator κ-(BEDT-TTF)2Cu2(CN)3. Phys. Rev. B 2010, 82, doi:10.1103/PhysRevB.82.125119.
[6]
Niizeki, S.; Yoshikane, F.; Kohno, K.; Takahashi, K.; Mori, H.; Bando, Y.; Kawamoto, T.; Mori, T. Dielectric Response and Electric-Field-Induced Metastable State in an Organic Conductor β-(meso-DMBEDT-TTF)2PF6. J. Phys. Soc. Jpn. 2008, 77, 073710, doi:10.1143/JPSJ.77.073710.
[7]
Mori, T.; Inokuchi, H. Structural and electrical properties of (BEDT-TTF)(TCNQ). Solid State Commun. 1986, 59, 355–359, doi:10.1016/0038-1098(86)90562-4.
[8]
Iwasa, Y.; Mizuhashi, K.; Koda, T.; Tokura, Y.; Saito, G. Metal-insulator transition and antiferromagnetic order in bis(ethylenedithio)tetrathiafulvalene tetracyanoquinodimethane (BEDT-TTF)(TCNQ). Phys. Rev. B 1994, 49, 3580–3583, doi:10.1103/PhysRevB.49.3580.
[9]
Sakai, M.; Sakuma, H.; Ito, Y.; Saito, A.; Nakamura, M.; Kudo, K. Ambipolar field-effect transistor characteristics of (BEDT-TTF)(TCNQ) crystals and metal-like conduction induced by a gate electric field. Phys. Rev. B 2007, 76 045111-1-045111-1-5., 045111–1, doi:10.1103/PhysRevB.76.045111.
[10]
Sakai, M.; Ito, Y.; Takahara, T.; Ishiguro, M.; Nakamura, M.; Kudo, K. Ferroelectriclike dielectric response and metal-insulator transition in organic Mott insulator-gate insulator interface. J. Appl. Phys. 2010, 107 043711-1-043711-5., 043711–1, doi:10.1063/1.3310735.
[11]
Mori, T.; Inokuchi, H. Crystal Structure of the Mixed-Stacked Salt of Bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF) and Tetracyanoquinodimethane (TCNQ). Bull. Chem. Soc. Jpn. 1987, 60, 402–404, doi:10.1246/bcsj.60.402.
[12]
Yamamoto, H.M.; Hagiwara, M.; Kato, R. New phase of (BEDT-TTF)(TCNQ). Synth. Met 2003, n133-134, 449–451.
[13]
Yamamoto, H.M.; Tajima, N.; Hagiwara, M.; Kato, R.; Yamaura, J.-I. Strange Electric/Magnetic Behavior of New (BEDT-TTF)(TCNQ). Synth. Met. 2003, 135-136, 623–624, doi:10.1016/S0379-6779(02)00808-1.
[14]
Brazovskii, S.; Monceau, P.; Nad, F. The ferroelectric Mott-Hubbard phase in organic conductors. Synth. Met. 2003, 137, 1331–1333, doi:10.1016/S0379-6779(02)01076-7.
[15]
Monceau, P.; Nad, F.; Brazovskii, S. Ferroelectric mott-hubbard phase of organic (TMTTF)2X conductors. Phys. Rev. Lett. 2001, 86, 4080–4083, doi:10.1103/PhysRevLett.86.4080.
[16]
Nad, F.; Monceau, P.; Carcel, C.; Fabre, J.M. Dielectric response of the charge-induced correlated state in the quasi-one-dimensional conductor (TMTTF)2PF6. Phys. Rev. B 2000, 62, 1753–1756, doi:10.1103/PhysRevB.62.1753.
[17]
Nad, F.; Monceau, P.; Fabre, J.M. Low frequency dielectric permittivity of quasi-one-dimensional conductor (TMTTF)2Br. Eur. Phys. J. B 1998, 3, 301–306, doi:10.1007/s100510050316.
[18]
Nad, F.; Monceau, P.; Bechgaard, K. Low-frequency permittivity of spin-density wave in (TMTSF)2PF6 at low temperatures. Solid State Commun. 1995, 95, 655–660, doi:10.1016/0038-1098(95)00360-6.
[19]
Nad, F.; Monceau, P. Charge-density-wave glass state in quasi-one-dimensional conductors. Phys. Rev. B 1995, 51, 2052–2060, doi:10.1103/PhysRevB.51.2052.
[20]
Fukazawa, H.; Hoshikawa, A.; Ishii, Y.; Chakoumakos, B.C.; Fernandez-Baca, J.A. Existence of Ferroelectric Ice in the Universe. Astrophys. J. 2006, 652, L57–L60, doi:10.1086/510017.
[21]
Yoshioka, H.; Tsuchiizu, M.; Seo, H. Charge-Ordered State versus Dimer-Mott Insulator at Finite Temperatures. J. Phys. Soc. Jpn. 2007, 76 103701-1-103701-4., 103701–1, doi:10.1143/JPSJ.76.103701.
[22]
Seo, H.; Motome, Y.; Kato, T. Finite-Temperature Phase Transitions in Quasi-One-Dimensional Molecular Conductors. J. Phys. Soc. Jpn. 2007, 76 013707-1-013707-6., 013707–1, doi:10.1143/JPSJ.76.013707.
[23]
Otsuka, Y.; Seo, H.; Motome, Y.; Kato, T. Finite-Temperature Phase Diagram of Quasi-One-Dimensional Molecular Conductors: Quantum Monte Carlo Study. J. Phys. Soc. Jpn. 2008, 77 113705-1-4., 113705–1, doi:10.1143/JPSJ.77.113705.
[24]
Kawasugi, Y.; Yamamoto, H.M.; Hosoda, M.; Tajima, N.; Fukunaga, T.; Tsukagoshi, K.; Kato, R. Strain-Induced Superconductor/Insulator Transition and Field Effect in a Thin Single Crystal of Molecular Conductor. Appl. Phys. Lett. 2008, 92 243508-1-243508-3., 243508–1, doi:10.1063/1.2949316.
[25]
Kawasugi, Y.; Yamamoto, H.M.; Tajima, N.; Fukunaga, T.; Tsukagoshi, K.; Kato, R. Field-Induced Carrier Delocalization in the Strain-Induced Mott Insulating State of an Organic Superconductor. Phys. Rev. Lett. 2009, 103 116801-1-116801-1-4., 116801–1, doi:10.1103/PhysRevLett.103.116801. 19792389
