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Mott FET ITRS Workshop on Emerging Research Logic Devices Bordeaux, France, September 21, 2012 A. Sawa 1,2 S. Asanuma, 1,2 P.-H. Xiang, 1,2 I. H. Inoue,

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Presentation on theme: "Mott FET ITRS Workshop on Emerging Research Logic Devices Bordeaux, France, September 21, 2012 A. Sawa 1,2 S. Asanuma, 1,2 P.-H. Xiang, 1,2 I. H. Inoue,"— Presentation transcript:

1 Mott FET ITRS Workshop on Emerging Research Logic Devices Bordeaux, France, September 21, 2012 A. Sawa 1,2 S. Asanuma, 1,2 P.-H. Xiang, 1,2 I. H. Inoue, 1,2 H. Yamada, 1 H. Sato, 1,2 and H. Akoh 1,2 1 National Institute of Advanced Industrial Science and Technology (AIST) 2 JST-CREST

2 Outline ・ Correlated electron system ・ Mott metal-insulator transition ・ Mott field effect transistor Feature/potential Issues/challenges ・ Experiments Mn-oxides Ni-oxides V-oxides ・ Summary

3 Correlated electron system Band insulator E EFEF electron Mott insulator t on-site Coulomb repulsion One electron in an orbital due to on-site Coulomb repulsion (U > t) E EFEF t: Transfer U: Coulomb Pauli’s rule No more than 2 electrons in an orbital E EFEF U upper Hubbard band (UHB) lower Hubbard band (LHB) electron orbital

4 Mott insulator-metal transition E EFEF W U Mott insulator Correlated-electron metal W < UW > U Mott transition W: band width U: Coulomb energy E EFEF W U W ∝ tW ∝ t t (t < U)(t > U) electron Electron solid Electron liquid Carrier doping, magnetic field, light, ・・・ light, ・・・ Decrease in U (band gap) Huge resistance change Y. Tomioka, unpublished

5 T Carrier density Antiferromagnetic insulator Critical point Electronic phases T Carrier density Paramagnetic metal Quantum CP (La,Sr)MnO 3 Superconductivity Changes in electronic, magnetic, and optical properties Optical property Magnetizum Ferromagnetic metal Antiferromagnetic insulator metal

6 Mott FET

7 Mott FET can control electronic, magnetic, and optical properties by electric field Gate Correlated-electron material Drain Source “ON” “OFF” “electronic”“magnetic” “optical”

8 Mott transition/transistor ‐ Scaling? ‐ Metal ON Insulator OFF Mott transition Number of electrons 10 3 electrons 4 nm In principle, a nanometer-scale Mott insulator shows the Mott transition No one has demonstrated ElectronsolidElectronliquid

9 Kotliar et.al PRL 89, (2002). First order phase transition Hysteretic behavior Nonvolatile(?) V < 0 V > 0 electrode doped-Mott ins. Oka, Nagaosa, PRL95, (2005) Mott transition/transistor ‐ Nonvolatile? ‐ No one has demonstrated

10 Matsubara et al., PRL99, (2007) Reflectcance Electronic state Karr rotation Magnetic state Mott transition takes place within a few picoseconds Sample: Gd 0.55 Sr 0.45 MnO 3 Mott transition/transistor ‐ Fast switching? ‐ Ultrafast optical pump ‐ probe spectroscopy

11 Challenges conventional gate dielectric (SiO 2 ): ~10 13 /cm 2 For the realization of a practical Mott transistor, Correlated-electron materials with a MI transition attainable at significantly lower carrier concentrationsCorrelated-electron materials with a MI transition attainable at significantly lower carrier concentrations High-k gate materials with a large breakdown strengthHigh-k gate materials with a large breakdown strength Ahn, Triscone, Mannhart, Nature 424, 1015 (2003) – cm -2

12 Electric double layer transistor

13 Outer Helmholtz plane J. T. Ye et al., Nature Mater. 9, 125 (2010) S. Ono et al., APL 94, (2009) a large amount of carriers: – cm -2 Electric double layer transistor Electrolyte/ionic liquid is used as gate dielectrics Large capacitance: > 10  F/cm 2

14 CMO channel Thickness: ~ 30 nm W/L: ~ 10μm/100μm + − DEME + cation TFSI - anion GDS ++++ − −−− Ionic Liquid Sepa- rator − − CMO IDID IGIG VDVD VGVG YAO substrate 10  F/cm -3 Hz →1.5 × /cm G = 2.5 V Electric double layer transistor (EDLT) S. Asamuna, AS et al., Appl. Phys. Lett. 97, (2010) P-.H. Xiang, AS et al., Adv. Mater. 23, 5822 (2011)

15 Insulator Metal Thickness of channel : 40nm On/Off ratio: >10 >10 P-.H. Xiang, AS et al., Adv. Mater. 23, 5822 (2011) Nonvolatile change in resistance at “room temperature” EDLT consisting of compressively strained CaMnO 3 film

16 New approach for Mott transistor Sheet Resistance Temperature ·CMR-manganite, High T C cuprate ·10 14 ~ /cm 2 carriers non-doped (V G = 0) carrier doped (V G ≠ 0) Sheet Resistance (logarithmic scale) Temperature “sharp” and “large” resistance change (Nd,Sm)NiO 3 T MI = 200–400 K VO 2 T MI = 300–340 K T MI

17 NdNiO 3 EDLT S. Asamuna, AS et al., Appl. Phys. Lett. 97, (2010)R. Scherwitzl et al., Adv. Mater. 22, 5517 (2010).

18 Nd 0.5 Sm 0.5 NiO 3 EDLT NSNO(0.5)/NdGaO 3 (110) (Thickness:~6 nm) Resistivity(  cm) Temperature (K) V -2.3V -2.5V (Nd,Sm)NiO 3 channel VGVG Temperature (ºC) Large resistance change (~10 5 ) at room temperature S. Asamuna, AS et al., unpublished I SD (A) V G K

19 ¥ Nonvolatile insulator metal Gate voltage VO 2 VO 2 EDLT Nakano et al., Nature 487, 459 (2012)

20 Oxide FET Mott FET SrTiO 3 TiO 2 (anatase) In-Ga-Zn-O GdBa 2 Cu 3 O 7 (La,Sr)MnO 3 Operation temperature On/Off ratio Gate material SrTiO 3 References R. T. ~ a-LaAlO 3 /MgO R. T. Gate voltage (V) Mobility (cm 2 /Vs) 5 APL92, (2008) ~102.5~10 5 a-CaHfO 3 JJAP46, L515 (2007) La 2 CuO 4 R. T.(?)<10<8SrTiO 3 APL76, 3632 (2000) (La,Ca)MnO 3 SrRu 1-x Ti x O 3 77K R. T. <10 <1 ±10PZT APL82, 4770 (2003) superconductivity: T C ~0.3K at V G =-3Velectrolyte Nat. Mater. 7, 855 (2008) K<10±3 PRL102, (2009) PZT (ferroelectrics ) K<3±3 Science 284, 1152 (1999) K<3±1PZT PRB74, (2006) ~ a-Y 2 O 3 APL89, (2006) Channel KTaO 3 ~ a-Al 2 O 3 R. T.100 APL84, 3726 (2004) CaMnO 3 50K R. T. >10 3 ~10 ±2 Adv. Mater. 23, 5822 (2011) (Nd,Sm)NiO 3 ~100K>10±2.5Ionic liquid APL97, (2010) Ionic liquid NdNiO 3 ±2.5Ionic liquid unpublished VO 2 260K ~10 3 R. T.~10 5 Ionic liquid±3 Nature 487, 459 (2012)

21 Feature/potential of Mott FET Functionality: electronic, magnetic, and optical switchesFunctionality: electronic, magnetic, and optical switches Scaling limit: < 10 nmScaling limit: < 10 nm Nonvolatile and fast switchingNonvolatile and fast switching Bottleneck/challenge A large number of carriers (>10 14 cm -2 ) is necessary to be doped in order to induce the Mott transition Summary For the realization of a practical Mott transistor (“solid”) Higk-k gate materials with a large breakdown strength(“solid”) Higk-k gate materials with a large breakdown strength expected from theoretical and experimental studies on correlated electron materials


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