1. 30 nm © 2005 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice Atomic Switch ITRS Emerging Research Devices Philip Kuekes Hewlett-Packard Labs

2. 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. 3 Ionic and electronic switching cation-migration electrochemical growth and dissolution of metallic filaments

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

5. 5 Pt TiO 2 TiO 2-x 3 nm 2 nm Ionic and electronic switching 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. 6 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 Metal/TiOx/Metal Device Physics

7. 7 50 nanometer Pt/TiOx/Pt devices a b Virgin I-V c 50 nm hp +V push O V vacancies -V attract O V vacancies Pt TiO 2 TiO x V + - Switching I-V TiOx Pt TiO2 Pt

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

9. 9 What is TiO 2-x ? 2 – TiOx controlled by oxygen vacancies rutile TiO2 3.0/3.2 eV semiconductor TiO 2-x : x ~ 10 -3 – 10 -2 dopants all ionized E i < 0.1 eV oxygen vacancies V O 2+ @ low T < 800C & high P(O 2 ) and Ti interstitials Ti i 4+ @ high T > 1000C & low P(O 2 ): creation ~ 3-5 eV diffusion ~ 0.7 - 1.1 eV mobility ~ 10 -10 – 10 -14 cm 2 /Vs

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

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

12. 12 Schottky barrier switching via oxygen vacancy drift TiOx Pt TiO2 Pt 7 nm TiO 2 Pt w ΦbΦb TiO 2 Pt w ΦbΦb TiO X Current (mA) II Current (mA) II

13. page 13 Pt TiO 2 TiO 2-x 3 nm 2 nm O vacancy drift model for TiOx switch Pt TiO 2 TiO 2-x oxidized reduced 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. 3 – Theory of vacancy drift fits experiment

14. page 14 O vacancy drift model for TiOx switch

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

16. 16 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 Metal/TiOx/Metal Device Physics

17. 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. 18 Where Silicon cant go 3D Nonvolatile

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