Seminar Presentation on MEMRISTOR

“The Fourth Basic Circuit Element”

By-Helal Uddin MullahMtech 2nd SemesterMTV/EC13/05mullahz251@gmail.com

Contents

What is Memristor?

History

Theory

Construction & Working

An analogy

Properties

Applications

Advantages

Conclusion

References

2

WHAT IS MEMRISTOR?

• A memristor is a semiconductor whose resistance varies as a function of flux and

current. This allows it to “remember” what has passed through the circuit.

• It is the fourth fundamental circuit element.

• Two terminal device.

• Its resistance depends on the amount of

charge passed through it.

• That’s why it is called “memristor”(memory resistor).

3

Memristor

Memristance• Memristance is simply charge-dependent resistance.

• Unit - ohm (Ω)

• Symbol

V(t) = M(q(t))*I(t)

Emergence Of Memristic Theory

• Theory was developed in 1971 by Professor Leon Chua at University of California, Berkeley.

• Found while exploring symmetry between the three fundamental passive linear circuit elements.

• In 2006, R.Stanley Williams developed practical model.

Three Fundamental Circuit Elements

Resistor

v R i

Capacitor

q C v

Inductor

L i

ResistorGeorg Ohm 1827

Capacitorvon Kleist 1745

InductorMichael Faraday 1831

Symmetry Of Relationships

Memristors

Φ=Mq

Voltage (V)

Current(i)

Charge (q) Flux (Φ)

Φ = Li Inductors

v=dΦ/dt i=dq/dt

Resistors

v=Ri

q=CvCapacitors

Theory

Or

Or

9

Working of TiO2 Based Memristor

Pt TiTiOv(2-x)

TiO2

3 nm

2 nm

dopeddepleted

(-)ve (+)ve

The HP device is composed of a thin (50 nm) titanium dioxide 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 doped of oxygen atoms.

The oxygen vacancies act as charge carriers, meaning that the doped layer has a

much lower resistance than the non- depleted layer.

When an electric field is applied, the oxygen vacancies drift ,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.

Memristance is displayed only when both the

doped and depleted layers contribute to resistance.

At a point of time, when enough charge will flow

in the film, no ion will be moving then the device enters

in to saturation and gives a constant value of M(q)

and remains fixed until we reverse the direction of

current flow.

In this TiO2 Memristor model, for RON<<ROFF

The memristance is

Where

μv = mobility of dopantD= thickness of the film.

Equivalent Circuit.

• Retain its resistance level even after power had

been shut down.

• Remember (or recall) the last resistance it had,

before being shut off.

• By changing the speed and strength of the

current, it is possible to change the behavior of

the device.

• A fast and hard current causes it to act as a

digital device.

• A soft and slow current causes it to act as an

analog device.

Property Of Memristor

Applications

As a switch

As a non volatile memory

Can perform logic operations

In artificial neural networks

13

1 cm3 of memristor = 1 terabit

Benefits Of Memristor Technology

• Would allow for a quicker boot up since information is not lost when the device is

turned off.

• Uses less power and produces less heat.

• Eliminates the need to write computer programs that replicate small parts of the

brain.

• Density allows for more information to be stored.

• Provides greater resiliency and reliability when power is interrupted in data centers.

• Creating a Analog Computer that works much faster than Digital ones.

• Conventional devices use only 0 and 1; Memristor can use anything between 0 and

1.

• Faster than Flash memory.

Allow digital cameras to take pictures with no delay in between.

• Compatible with current CMOS interfaces.

Not Perfect Yet !• Though hundreds of thousands of memristor

semiconductors have already been built, there is still

much more to be perfected.

• Needs more defect engineering.

• No design standards (rules).

Conclusion

In April 2010, HP labs announced that they had practical memristors working at

1 ns (~1 GHz) switching times and 3 nm by 3 nm sizes, which bodes well for

the future of the technology.At these densities it could easily rival the current

sub-25 nm flash memory technology.

So,it is sure that Memristor will change circuit design in the 21st century as radically

as the transistor changed it in the 20th.

As scientist are saying that Moore’s law is going to be saturated by 2022, we will now

have memristors as alternative to transistors.

Finally as Leon O Chua mentioned “It’s time to rewrite all the EE textbooks”

References

• L. O. Chua, “Memristor-the missing circuit element,” IEEE Trans. Circuit Theory,

vol. 18,pp. 507 -519, Sep. 1971.

• D. B. Strukov, G. S. Snider, D. R. Stewart, and R. S. Williams, “The missing

memristor found.," Nature, vol. 453, no. 7191, pp. 80 -83, 2008.

• M. Di Ventra, Yu. V. Pershin, L. O. Chua, “Circuit elements with memory:

memristors, memcapacitors and meminductors”. 2009. arXiv:0901.3682.

• L. O. Chua, “Resistance switching memories are memristors," Appl. Phys. A, vol.

102,pp. 765-783, 2011.

• http://en.wikipedia.org/wiki/Memristor

17