Memristors and Memristic Systems

8/7/2019 Memristors and Memristic Systems

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� A memristor is a semiconductor whoseresistance varies as a function of flux andcurrent. This allows it to ³remember´ what

has passed through the circuit.� This technology may replace transistors,

N AND flash memory, and even digital

logic as we know it.� Emerging technology in working prototypephase.



� Physics behind memristic theory

� Chemistry behind memristic design

� Future technologies and potential of memrisitic systems



� Theory developed in 1971 by Professor

Leon Chua of U. C. Berkeley

� Found while exploring symmetry betweenthe three fundamental passive linear

circuit elements.



� Voltage, V (V) ± potential difference

between two points.

� Current, I ( A) ± flow of electric charge� Flux, (W) ± rate of flow through an area

� Charge, Q (C) ± energy per electron



� Current is the derivative of Charge

� Voltage is the derivative of Flux



V I

Q



� Capacitor,C (F)

� Resistor,R ()

� Inductor,L (H)

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V I

Q

Capacitors q=Cv



� Ohm¶s

Law

� v = R i

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� = L i

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V I

Q

Capacitors q=Cv

Resistors

v=Ri

Inductors=Li

v=d/dt i=dq/dt

?

?



Fundamental Memrisitive System Theorem:

� Any two-terminal device which exhibits a

pinched hysteresis loop in the voltage vs.current plane, thereby relating charge and

flux.

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� = M q

� d/dt = M(q) dq/dt

� V(t) = M(q) I� P = I V

� P = I² M(q)

� P = I² R

Symbol of a menristor



V I

Q

Capacitors q=Cv

Resistors

v=Ri

Inductors=Li

v=d/dt i=dq/dt

=Mq

Memristors



� The number of

transistors that

can be placed

inexpensively on

an integrated

circuit has

doubledapproximately

every two years.By Moore¶s law

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� O Vacancy Drift Model for TiOv(2-x) Switch (Developedby R. Stanley Williams of HP Labs, 2008)

PT PTTiOv(2-x)

TiO2

3 nm

2 nm

Oxidized

Reduced



� The HP device is composed of a thin (50 nm) titaniumdioxide film between two 5 nm thick electrodes, one Ti,

the other Pt. Initially, there are two layers to the titanium

dioxide film, one of which has a slight depletion of

oxygen atoms. The oxygen vacancies act as charge

carriers, meaning that the depleted layer has a muchlower resistance than the non-depleted layer. When an

electric field is applied, the oxygen vacancies drift (see

Fast ion conductor ), changing the boundary between the

high-resistance and low-resistance layers. Thus the

resistance of the film as a whole is dependent on how

much charge has been passed through it in a particular

direction, which is reversible by changing the direction of

current.[



� Have great data density.

� 100 GBs of memory made from memristors on

same area of 16 GBs of flash memory.

� Creating a Computer that never has toboot up.

� Does not lose information when turned off.

� Has the capacity to remember the chargethat flows through it at a given point in

time.



� Compatible with current CMOS interfaces

� Power Consumption

± As non-volatile memory, memristors do not consume

power when idle.

� Size

± 3 Memristors to make a N AND gate

± 27 N AND gates to make a Memristor

± CMOS N AND Area 36 x (FP)² = .3µ² @ 45 nm

± Memristor N AND Area 3 x (FP)² = .05µ² @ 45 nm



� Though hundreds of thousands of memristor

semiconductors have already been built, there is

still much more to be perfected.

� Dissipates heat when being written to or read.

� Needs more defect engineering.

� No design standards (rules).

� Fair endurance (overlookable e.g.. Transistors).



� Hope to one day have a computer thatprocesses information in the same way asthe human brain.

� Could lead to the replacement of thetransistor.

� Used in common devices for unbelievable

storage.� Appliances that ³learn´ from experiences.





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Memristors and Memristic Systems