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30 nmPhysics and

Materials Science

devices

Hewlett-Packard Laboratories, Palo AltoCA

2005 Hewlett-Packard Development Company, L.P.

The information contained herein is subject to change without notice

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People

Jianhua Yang;

Julien Borghetti;

John Paul Stracham;

Dou Ohlber ;

Duncan Stewart;

Phil Kuekes;

Stan Williams;

2

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Outline

Memristor definition;

Implementation;

3

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History

Memory effect in early MIM junctions (Au:SiO):

4by Simmons and Verderber, Proc. Royal Society of London A, 301 (19671967) 77

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Currently.

Stanford, U. Houston, Achen, Julich, Universit Paris-, ,

AMD, HP, IBM, Motorola, Samsung, Sharp

5

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3 fundamental circuit elements

Resistor 1827

Georg Ohm

RESISTOR CAPACITORCv= R i q= C v

INDUCTOR = L i

Capacitor - 1745

Volta / von Kleist & van Musschenbroek

Benjamin Franklin

page 6

Faraday

Joseph Henry

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3 fundamental circuit elements

v1827 1745

RESISTOR CAPACITORC

d/dt

v= R i q= C vdq/dt= i

=v

i q

INDUCTOR = L i

1831

page 7

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Leon Chua 1971

v1827 1745

RESISTOR CAPACITORC

d/dt

v= R i q= C vdq/dt= i

=v

i q

INDUCTOR = L i

?

1831

page 8

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Leon Chua 1971 the memristor

v1827 1745

RESISTOR CAPACITORC

d/dt

v= R i q= C vdq/dt= i

=v

iq

INDUCTOR = L i

MEMRISTOR =M q

1831

page 9

L. O. Chua, Memristor - the missing circuit element, IEEE Trans. Circuit Theory 18, 507519 (1971).L. O. Chua and S. M. Kang, "Memristive devices and systems," Proc. IEEE, 64 (2), 209-23 (1976).

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Leon Chua 1971 the memristor

v Simple Memristor:1827 1745

RESISTOR CAPACITORC

d/dt

iwMv )(=dwv= R i q= C v

dq/dt= i

=v

iq

dt

INDUCTOR = L i

MEMRISTOR =M q

Generalized Memristor

(Memristive system):

MEMRISTIVE SYSTEMS

,( , )

dwf w i=

1831

page 10

L. O. Chua, Memristor - the missing circuit element, IEEE Trans. Circuit Theory 18, 507519 (1971).L. O. Chua and S. M. Kang, "Memristive devices and systems," Proc. IEEE, 64 (2), 209-23 (1976).

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Leon Chua 1971 the memristor

v Simple Memristor:1827 1745

RESISTOR CAPACITORC

d/dt

iwMv )(=dwv= R i q= C v

dq/dt= i

=v

iq

dt

INDUCTOR = L i

MEMRISTOR =M q

MEMRISTIVE SYSTEMS1831

page 11

L. O. Chua, Memristor - the missing circuit element, IEEE Trans. Circuit Theory 18, 507519 (1971).L. O. Chua and S. M. Kang, "Memristive devices and systems," Proc. IEEE, 64 (2), 209-23 (1976).

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Implementation

Modulation of electronic transport;

Dynamic electronics;

page 12

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TiO2

rutile TiO2

3.0/3.2 eV semiconductordielectric ~ 80, bi-refringent

pigment, photocatalyst, O2 sensors

TiO2

: 1x Ti4+ + 2x O2-

anatase TiO2

13

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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 eVdiffusion ~ 0.7 - 1.1 eV

- -

14

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O vacancy drift model for TiOx switch

undoped

w

Vdoped

A

ONV

( )( )

Rdw ti t

dt L=

ONV

( ) ( )R

w t q t L

= )()(

1)(

)( OFFON tiL

twR

L

twRtv

+=

L

0.5

1.0

tage 5

10

current

0.60.50.40.30.20.10.0 time (10

3

)

RESISTORv=R i

CAPACITORq= C v

d/dt

=v

v

1.0

0.5w/L

-1.0

-0.5

.vol

-10-5

(10

-3

)

INDUCTOR = L i

MEMRISTOR =M q

dq/dt= ii q

0.0

0.60.50.40.30.20.10.0

time (103)

MEMRISTIVE SYSTEMS

0

5

rrent(10-3)

.

0.40.20.0

char

g

500flux

page 15

-10

-c

-1.0 -0.5 0.0 0.5 1.0

voltage

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O vacancy drift model for TiOx switch

undoped

w

Vdoped

A

ONV

( )( )

Rdw ti t

dt L=

ONV

( ) ( )R

w t q t L

= )()(

1)(

)( OFFON tiL

twR

L

twRtv

+=

L

0.5

1.0

tage 5

10

current

0.60.50.40.30.20.10.0 time (10

3

)

RESISTORv=R i

CAPACITORq= C v

d/dt

=v

v

1.0

0.5w/L

-1.0

-0.5

.vol

-10-5

(10

-3

)

INDUCTOR = L i

MEMRISTOR =M q

dq/dt= ii q

0.0

0.60.50.40.30.20.10.0

time (103)

Generalized Memristor

MEMRISTIVE SYSTEMS

0

5

rrent(10-3)

.

0.40.20.0

char

g

500flux ivwMv ),(=

(Memristive system):

page 16

-10

-c

-1.0 -0.5 0.0 0.5 1.0

voltage

( , )f w i

dt

=

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O vacancy drift model for TiOx switch

undoped

w

Vdoped

A

L

1.61.20.80.40.0

time (103)

-1

0

1

v

oltage

1.0

0.5

0.0

w/

L

1.61.20.80.40.0

0.5

1.0

t

ROFF/RON = 50

v = 4 V

-0.5

0.0curre

n

page 17

- .

-1.0 -0.5 0.0 0.5 1.0

voltage

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O vacancy drift model for TiOx switch

undoped

w

Vdoped

A

L

41.61.20.80.40.0

time (103)

47

Pt PtExpt Expt

2

t(mA

)-1

0

voltage

1.61.20.80.40.0

.

0.5

0.0

w/

L 2

t(m

A) 1

2345Ti

Pt

Ti

Pt

-2

C

urren

0.0

0.5

1.0

current

ROFF/RON = 50

v0 = 4 V

-2

Curren

9

10

17

-4

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5Voltage (V)

-1.0

- .

-1.0 -0.5 0.0 0.5 1.0voltage

-4

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5Voltage (V)

8

page 18

Dmitri Strukov, Greg Snider,

Duncan Stewart, R. Stanley Williams,Nature453, 80 - 83 (01 May 2008)

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Device operation

Electroforming and bubbling

Endurance

Scalability;page 19

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O2 reduction at anode creates bubbles

-

20

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O2 bubble movie

click for movie

21

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Electroforming can induce O2 reduction

Anode (+)Cathode (-)Anode

Where oxidation occurs

2e-

TiO2+ O2

Oxygen is oxidized from

-

TiO2

22

E

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Electroforming can induce O2 reduction

Anode (+)Cathode (-)

O2TiO2+2

O2O2O2

TiO2+

TiO2+

TiO +

TiO2+

TiO22

bubble

23

E

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Nano-devices do NOT show bubbles

1530

)

Micron-sized Nano-sized

200100

10

5

0

Z(nm)

800040000

15

0

X (nm)

Z(n

TE

X (nm)

BE

BE

4

100

50

0

Z(nm)

TE

X (nm)

TE

24

BE

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Endurance: 200-400 traces on 50

nanometer Pt/TiOx/Pt devices

200a c +V pushPt

100

V vacanc esSwitching I-V

TiOx

0

urrent

(uA)

4)b

50 nm hp-V attract

OV vacancies

-3

Pt

-100

C

2

urrent

(nA

10-6

10-9

Pt

TiO2TiOx

V

+

-

-200-2 -1 0 1 2

Voltage ( V )

C

-2 -1 0 1 2Voltage ( V )

rg n - -1 0 1

25

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Role of interface: Devices on

Sin le cr stal TiO Pre arationSingle crystal TiO2 rutile

was annealed at 700 oC

Create Vo2+ by annealing

TiO2 bulk crystal, Rutile

2 2

1 2

3 4Ti+TiO2=>TiO2-x creating Vo

2+Ti

Pt

Create more Vo2+ locally by Ti

I3-4

TiO2 bulk crystal

Many two-terminal permutations (devices)

Pt PtTi Ti

Pt Pt

TiO2

1

2 3

4 V

+

-

J. Joshua Yang 26

TiO2-X

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+

I2-3

Pt Pt1

2 3

4

-

V

TiO2

1

TiO2-X

TiO2Pt

w

b

w

TiO2-X

TiO2Pt TiO2Ti

b

J. Joshua Yang 27

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Role of interface: I-V curves

2 3-

V

+

I2-310

(mA)

2-3

Pt PtTi Ti

Pt Pt

TiO2-X

TiO2

4

TiO2-x

TiPt

Ti

2

-

0

Current

identical contacts Symmetric I-V;

5nmTi/TiO2Ohmic contacts (Pads 2,3);

The single crystal TiO2 is very conductive;

I1-4

-0.4 0.0 0.4Voltage (V)

Pt PtTi Ti

Pt Pt1

2 3

4-

V

+

500

(nA) 1-4

TiO2-X

TiO2

-500Curren

1

4Pt

TiO2-x

Pt

J. Joshua Yang 28

-

Pt/TiO2Schottky contact (pads 1,4);

Interfaces dominates the I-V (bulk TiO2 contact). -0.4 0.0 0.4

V oltag e (V)

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Role of interface: I-V curves

0

I2-4

-200

rrent(

A) - Gnd

2Pt PtTi Ti

Pt Pt

TiO2

1 4 V

-

TiO2-x

TiPt

-400

C

-0.4 0 0.4

42-X

I2-3

Pt

400

A)

1-3GndPt Pt1

2 3

4

-

V

+

200

Current

(

3

Pt PtTi Ti

TiO2-X

TiO2

Pt

TiO2-xTi

J. Joshua Yang 29

0

-0.4 0.0 0.4V oltage (V)

S f

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Scalability: from micron- to nano-

cross oint unctions5x5 micronmeter2 50x50 nanometer2

50 nm

10~100nm

TiO2-xAV

half-pitchHP Labs

200 OFF

500m

20

OFF10

-3

100

(uA) 10

-9

10-7

10-

-2.0 -1.0 0.0 1.0

10

ent(mA)

10-7

10-5

-3 -2 -1 0 1

Large on/offratio (~103)

-100

Curren

ON

-10

C

urr

ON Fast (

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Conclusions

class of devices, that can be configured

New applications can be found inmemory, signal conditioning, etc.

page 31

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The end

page 32

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Switching features: localized or

Question: Is pad 4 uniformly or locally changed?!

42-4

2 3

V

I2-4

2

rre

nt(mA)

2-41

Pt Ti Ti

Pt Pt

TiO2-X

TiO2

141 42

0

-2

Cu

2-42

-1 0 1Voltage (V)

J. Joshua Yang 33