1. 금속 - 절연체 전이 (MIT) 현상의 규명 및 응용 김현탁 박사 ( 한국전자통신연구원 )

2. Hyun-Tak Kim, Bong-Jun Kim, Yong Wook Lee, Byung-Gue Chae, Sun-Jin Yun (ETRI) Kang-Jeon Han, Ki-ju Yee (Chunnam U.), Yong-Sick Lim (Konkuk U.) Problem: Metal-Insulator Transition (MIT) near U/U c =1 ? U/t Brinkman-RicePictureDiscontinuous(Jump) Hubbard Model Continuous UcUc Insulator Metal ω μ μ μ ω (U/t) c Mechanism and Applications of Metal-Insulator Transition (MIT) in VO 2 U=ee/r r

3. Metal, Semiconductor, Insulator ? Semiconductor Energy Gap Gap < 2 eV J=~ 10 2 ~3 A/cm 2 I V 0  /a k Insulator Energy Gap Gap > 3 eV 0  /a k Metal I V Resistance : electron-phonon interaction Energy EFEF Ohm’s law Free electron J=~ 10 7 ~8 A/cm 2 Band filling factor :  =1 0  /a k

4. Hole-driven MIT theory by Hyun-Tak Kim  Physica C 341-348 (2000) 259  Tokura et al., PRL 70 (1993) 2126 Extended Brinkman-Rice picture at  =U ’ /U c =1 m * /m  (Conductivity) 0.5 Mott Insulator Metal (Hole doping) MIT (Divergence; Jump) Band filling factor at  =1 1.0 Data LaTiO 3 1/(1-  ) 1/(1-  4 ) Sr 1-  La  TiO 3  =1  =0.99.. Violet : hole  =1

5. Physical meaning of Hole-driven MIT theory MIT electron Coulomb energy Mott Insulator @  =1 UcUc Metal @  1, Inhomogeneous U hole Breakdown of U electron Coulomb energy (U)  =1  =0.99..

6. Insulator Metal Jump (Divergence) Ohm ’ s law Charge Injection Process VO 2 7  m  70  : Series  Thickness : 100 nm 70  m Electrode  Endurance test 0.1A Time (hour) VO 2 5  m 50 Electrode Thickness : 100 nm J  2 x 10 6 A/cm 2 4 81216 0 V MIT =10V V +5 O 2 -2 V : 3d 1

7. Background VO 2 (3d 1 ) is Mott insulator or Peierls insulator ? (controversial). We should reveal whether the MIT and the SPT occur simultaneously or not ? e-ee-h Monoclinic Tetragonal Monoclinic Tetragonal 340K = 67 o C Up to now, It has been known MIT and SPT occurs simultaneously. I have an objection. Structural Phase Transition : SPT

8. 3μm3μm 20μm electrode VO 2 film 622, A g Monoclinic Micro-Raman Fig. A Fig. B Fig. C 10V, 20mA 10V, 2mA 0V Substrate MIT SPT 4 times Meas. Laser beam Simultaneously MIT occurs prior to SPT

9. MIT Mechanism : MIT is prior to SPT PRL 87(2001)237401 (Insulator) (Metal) SPT: 470  160 fs Metal peak Structural Phase Transition MIT Speed Change of Transmission

12. Programmable critical temperature sensor

14. 2006. 7. 13, 독일 드레스덴, 국제학회 (M2S-HTSC-VIII) 발표, cond-mat/0609033 Programmable 임계온도 스위치 및 적외선용 MoBRiK 소자 2006. 7. 13, 독일 드레스덴, 국제학회 (M2S-HTSC-VIII) 발표, cond-mat/0609033  화재감지, 모터 제어 센서, 산업 응용  적외선 센서 및 광소자 응용 16,000 소자 (@2-inch wafer) Cell: 300 x 300  m 2 세계최초 MIT 시작품 : 개발 MIT 소자 1 전극 2 전극 열전달 및 방열 단자 1.6 mm 0.8mm MoBRiK MIT 적외선 센서 VO 2

15. 임계온도 스위치 와 기존 시스템 비교 임계온도 스위치 기능 센서 + 제어 ( 릴레이, 부저, 트랜지스터 ) 장점 : 부품수가 절약  불량률 감소 저전력 (0.03mA, 기존 20mA) 제어 스피드가 빠름 부저부저 부저 센서

16. MIT 소자 5 개 직렬연결 MoBRiK 소자........... + + + SubstrateSourceElectrodeDrainElectrode MoBRiK 소자 이용 고전압 잡음제거 원리 ( 물질, 응용특허 )

17. 외부잡음신호 전원전원 전자시스템전자시스템 전원線 MoB RiK Insulator Metal 1,600~2,000V ESD 1KV 이하 응용 : MOSFET, SAW, OP-Amp, J-FET, GaAs FET, 초고주파 반도체 소자, C-MOS, SCR 등 MoBRiK 소자의 응용기술 : 고전압 고속 잡음 바이패스 0.7~1 ns W Commercial Device MoBRiK Device L

18. 1. Hole doping of a very low concentration to VO 2 causes an abrupt MIT, as predicted in the extended Brinkman-Rice picture. 2. Electric field and temperature are a means of excitation. 3. The abrupt MIT does not undergo the structure phase transition and is not explained by Peierls picture (electron-lattice interaction). 4. The abrupt MIT rather than a continuous MIT is intrinsic near Mott insulator (U c /U  1). 5. The abrupt MIT can provide very important future device applications. Conclusion