Niobium oxide and Vanadium oxide as unconventional Materials for Applications in neuromorphic Devices and Circuits

Transcription

1 Niobium oxide and Vanadium oxide as unconventional Materials for Applications in neuromorphic Devices and Circuits Martin Ziegler, Mirko Hansen, Marina Ignatov, Adrian Petraru, and Hermann Kohlstedt Nanoelektronik, Technische Fakultät, Christian Albrechts Universität zu Kiel, Germany Sven Dirkmann and Thomas Mussenbrock Ruhr Universität Bochum, Lehrstuhl für Theoretische Elektrotechnik, Germany FOR 2093 SPICE Workshop, Mainz,

2 A Brain replaced by Computer Chips c V = 1000 cm 3 A chip 1 cm 2 a b P = 50 W/chip N chips N transistors approx. number of synapses P total 10 6 W 1 MW (!) P brain 25 W P MOSFET 5nW P synapse 250 fw 2

3 Biological Systems Far from Equilibrium and in permanent interaction with environment Reaction Biological Nervous System Environment Data Input Light Sound Smell 3

4 Nanoelectronics and Information Technology Wiley,

5 Signal Pathway Nanoelectronics and Information Technology Wiley,

6 Action Potential: Spike 100 mv Speed 0.1 m/s 100 m/s Nervous Systems 3.5 ms 1 V Speed 2,5 x 10 8 m/s c 0 Computer 10 ns 6

7 Human Brain:10 14 Interconnections! Humans: Neurons 10 3 Synapses 7

8 Can memristive Devices mimic Synapses? Learning & Coupling Strength Spikes Biology Neurology C. S. Sherrington 1897 D. O. Hebb 1948 I V Theory Technology L. Chua 1971 HP Labs 2009 Ohno, Aono et al., Nature Mat Jo et al.,nanoletters

9 Cognitiv Complexity Levels Neurobiology A B Neuromorphic Engineering 9 Explicit Plasticity Hebbian Implicit Recurrent

10 Demonstration of Conditioning and Anticipation by using Memristive Devices Pavlov`s Dog IVAN PETROVICH PAVLOV (1905) M. Ziegler et al. Adv. Func. Mat 2012 O. Bichler et al. Neuro Comp The Granger Collection, NYC All rights reserved. 10

11 Demonstration of Conditioning and Anticipation by using Memristive Devices Y. V. Pershin, S. La Fontaine and M. Di Ventra, Phys. Rev. E (2009) T. Saigusa et al. Phys. Rev. Lett. (2008) M. Ziegler et al. Appl. Phys. A (2013) Amoeba anticipated events 11

12 Part I Vanadium dioxide VO 2 Part II Niobium oxide Nb x O y Neuromorphic Circuit (firing rate adaptation) Memristive Tunnel Junction (forming free) 12

13 Frequency Adaptation Edgar D. Adrian, J Physiol. (1926) Instrument of torture L. Du Preez, Struik Publishers, 2009 E. M. Izhikevich, Neural Networks,

14 Spiking neuron Y. W. Lee et al., Appl. Phys. Lett, 2008 M. Ignatov, M. Ziegler, M. Hansen et al. 14

15 Negative Differential Resistance in Vanadium di oxide Lateral Vanadium dioxide devices : VO 2 films by pulsed laser deposition Au Au Current source VO 2 2 Ti Yong Wook Lee et al., Appl. Phys. Lett. (2008) Driscoll et al., Phys. Rev. B (2012) A. Zimmers et al., Phys. Rev. Lett. (2013) 15

16 Frequency Coding R. Klinke et al., Physiologie. Thieme,

17 Memcapacitance Spiking Neuron M. Di Ventra, Y. Pershin, L. Chua, Proc. IEEE,

18 Frequency Adaptation E. M. Izhikevich, Neural Networks,

19 Back to the Circuitry Ag TiO 2 x Al set jump in frequency no smooth adaptation reset 1. Digital switch/forming precedure required/ filamentary driven/ 19

20 Ag TiO 2 x Al set MovieCycle01.avi reset 1. Thomas Mussenbrock Sven Dirkmann Martin Ziegler Pt TiO 2 x Ag 20

21 Conclusion Part I Realization of a memristive neuron circuit VO 2 enables all or nothing spiking and frequency coding Memcapacitance emulates frequency adaptation 21

22 Filaments and homogenous Interface Effect Two major classes of devices: filament based area based (aim: homogenous shift of an interface, high resistance) Advantages of area based devices no electroforming necessary on resistance scales with area possibly higher run to run reproducibility Overview on: Nanofilamentary resistive switching K. M. Kim, D. S. Jeong and C. S. Hwang, Nanotechnology

23 Requirements for Memristive Devices in Neuromorphic Circuits high resistance retention in the order of days weeks continuous / analog switching electroforming-free 23

24 Device Structure Limit resistive switching to interface effects by using thin insulating layers Au 2.5 nm Nb x O y Solid state electrolyte 1.3 nm Al 2 O 3 Al Nb Tunnel barrier M. Hansen, M. Ziegler, et al. submitted to Science Reports 24

25 Amorphous Al 2 O 3 Tunnel Barrier Well established Nb/Al AlO x technology for Josephson Junctions (low temperature superconducting electronics) Low Al 2 O 3 surface roughness for subsequent layers SIS I V curve Superconductor Insulator Superconductor in liquid 4.2 K Al 2 O 3 ( 1.3 nm) Al overlayer Nb Al Nb Gurvitch et al., Appl. Phys. Lett. 42, 472 (1983) 25

26 Device Limit resistive switching to interface effects by using thin insulating layers Au 2.5 nm 1.3 nm Nb x O y Al 2 O 3 Al reset set Nb 26

27 Homogeneous Switching R x A = const. indicates homogeneous switching A A filamnet Geometrical area defined by lithography 27

28 Possible Mechanisms 1. Charge injection and trapping 2. Ionic movement and change of interfacial properties Nb Nb J. G. Simmons, Proc. R. Soc. Lond. A, (1967) C. J. Kim,Thin Solid Films, 515, 2726 (2006) S. J. Baik, Appl. Phys. Lett., 97, (2010) D. S. Jeong, Solid-State Elect. 63, 1 (2011). 28

29 Interface Contribution Tunnel barrier Schottky barrier Nb Nb x O y Al 2 O 3 Al Nb Au Nb x O y Nb Schottky barrier + Tunnel barrier Au Nb x O y Al 2 O 3 Al Nb E. Mikheev et al., Nat. Comm (Schottky Barrier) 29

30 Model Band Diagram During set process, mobile oxygen ions increase interface potential V I and decrease effective barrier width d eff M. Hansen, M. Ziegler, et al. submitted to Science Reports 30

31 Equivalent Electrical Circuit Model Nb Tunnel barrier thickness: Dd variable: D D D d constant: Simulation Experiment 31

32 Conclusion Realization of a memristive neuron circuit VO 2 enables all or nothing spiking and frequency coding Memcapacitance emulates frequency adaptation Homogeneous change in resistance in very thin films Resistive switching by modification of Schottky and tunnel barrier properties Retention tuneable with barrier choice 32

33 Posters on this Topic Emulation of neuronal functionality using a VO2 based oscillator circuit Martin Ziegler Kinetic Monte Carlo Simulation of memresistive resistance switching devices Thomas Mussenbrock 33

34 Acknowledgement Filaments low resistance state (LRS) after electric forming Doo Seok Jeong Towards artificial neurons and synapses: a materials point of view RSC Advances

35 Memristive Devices for Neuronal Systems: Research Group 2093 Partners and Sponsor 35

36 References and references therein 36