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Atomic Switch ITRS Emerging Research Devices

Atomic Switch ITRS Emerging Research Devices. Philip Kuekes Hewlett-Packard Labs. Ionic and electronic switching. thermal, electrical or ion-migration-induced switching mechanisms Nanoionics-based resistive switching memories Rainer Waser & Masakazu Aono

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Atomic Switch ITRS Emerging Research Devices

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  1. Atomic SwitchITRSEmerging Research Devices Philip Kuekes Hewlett-Packard Labs

  2. Ionic and electronic switching • thermal, electrical or ion-migration-induced switching mechanisms • Nanoionics-based resistive switching memories Rainer Waser & Masakazu Aono Nat Mater. 2007 Nov ;6 (11):833-40

  3. Ionic and electronic switching • cation-migration • electrochemical growth and dissolution of metallic filaments

  4. Ionic and electronic switching • anion-migration • transition metal oxides • electronically conducting paths of sub-oxides • Schottky barrier

  5. Ionic and electronic switching 2 nm Pt TiO2 TiO2-x Pt 3 nm We used to think about fixed semiconductor structure and only electronic motion. Now we have ionic motion that dynamically modulates the semiconductor structure that controls the electronic current. Diodes needed in ON state!

  6. Metal/TiOx/Metal Device Physics • 1. Nano-device switching is due to TiOx • 2. TiOx switching is controlled by oxygen vacancy distribution • - TiOx is a semiconductor doped by oxygen vacancies • - charged oxygen vacancies drift under high field • - deliberate placement of oxygen vacancies can engineer the switching • - electroforming is a critical device step • 3. Dynamic theory of oxygen vacancy drift fits experiment • - oxygen vacancy distribution controls electron conductivity • - vacancy drift modulates junction conductance • - fundamental memristor theory matches experiment • - detailed dynamics are highly nonlinear • 4. New circuits enabled by these nano-switches • - NVRAM • - adaptive signal conditioning • - adaptive intelligent machines

  7. Pt TiOx TiO2 Pt a +V push OV vacancies c Switching I-V Pt + TiO2 V TiOx - Pt -V attract OV vacancies 50 nm hp b Virgin I-V 50 nanometer Pt/TiOx/Pt devices

  8. < 50 nanosecond Pt/TiOx/Pt devices t = 1 us t = 36 ns

  9. 2 – TiOx controlled by oxygen vacancies What is TiO2-x ? rutile TiO2 3.0/3.2 eV semiconductor TiO2-x : x ~ 10-3 – 10-2 dopants all ionized Ei < 0.1 eV oxygen vacancies VO2+@ low T < 800C & high P(O2) and Ti interstitials Tii4+@ high T > 1000C & low P(O2): creation ~ 3-5 eV diffusion ~ 0.7 - 1.1 eV mobility ~ 10-10 – 10-14 cm2/Vs

  10. Pt Pt TiO2 TiOx TiO2 TiOx Pt Pt Vacancies control electrical symmetry! a d I II Current (nA) Current (nA) 7 nm b 7 nm e I’ II’ Current (mA) Current (mA) Voltage (V) Voltage (V)

  11. Pt Pt TiOx TiO2 TiOx TiO2 Pt Pt Pt Pt Ti Ti TiOx TiO2 TiOx TiO2 Pt Pt Vacancies control electrical symmetry! a d I II Current (nA) Current (nA) 7 nm b 7 nm e I’ II’ Current (mA) Current (mA) c f IB IIB 5 nm Current (mA) Current (uA) Voltage (V) Voltage (V)

  12. Pt TiOx TiO2 Pt II’ w Current (mA) w TiOX Φb Φb TiO2 Pt Pt TiO2 II’ Current (mA) Schottky barrier switching via oxygen vacancy drift 7 nm 7 nm

  13. 3 – Theory of vacancy drift fits experiment O vacancy drift model for TiOx switch As fabricated, the oxide has a highly resistive TiO2 region and a conductive TiO2-x region that is highly doped with O vacancies, which are positively charged. When a positive bias voltage is applied to electrode 2, the positively charged O vacancies drift to the left, which narrows the tunneling gap. 2 nm Pt TiO2 TiO2-x Pt 3 nm Pt TiO2 TiO2-x Pt reduced oxidized

  14. O vacancy drift model for TiOx switch

  15. A w V doped undoped L Pt Pt Ti Ti Pt Pt O vacancy drift model for TiOx switch Expt Expt

  16. Metal/TiOx/Metal Device Physics • 1. Nano-device switching is due to TiOx • 2. TiOx switching is controlled by oxygen vacancy distribution • - TiOx is a semiconductor doped by oxygen vacancies • - charged oxygen vacancies drift under high field • - deliberate placement of oxygen vacancies can engineer the switching • -> electroforming is a critical device step • 3. Dynamic theory of oxygen vacancy drift fits experiment • - oxygen vacancy distribution controls electron conductivity • - vacancy drift modulates junction conductance • - fundamental memristor theory matches experiment • -> detailed dynamics are highly nonlinear • 4. New nano-circuits enabled by these nano-switches • - NVRAM • - latch circuits • - adaptive signal conditioning

  17. 3D - No Transistors • In ultra-dense nanoelectronic memory arrays, instead of the transistor “T.” a two terminal non-linear diode-like element may be used with a resistive memory element. Such structure is represented as 1D1R technology.

  18. Where Silicon can’t go • 3D • Nonvolatile

  19. Vision for Future Hybrid Chip: CMOS/NanoElectronics Atomic Switch Crossbar Multi-layers Si CMOS

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