Memristor Naveed Bashir Enroll no. 38/09 Roll no. 06 7th Semester Department of Electrical

Engg., NIT Srinagar.

V i

q φ

Voltage, V Current, AResistor:

Capacitor:Inductor:

Memristor:

MEMRISTOR-The Missing Circuit Element

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Memristance:-

property of an electronic component. If charge flows in one direction through a circuit, the resistance of that component of the circuit will increase, and if charge flows in the opposite direction in the circuit, the resistance will decrease.

If the flow of charge is stopped by turning off the applied voltage, the component will 'remember' the last resistance that it had

Memristor:-The Memristor is formally defined as a two-terminal passive

element in which the magnetic flux Φm between the terminals is a function of the amount of electric charge q that has passed through the device.

Exhibits memristanceElectronic symbol

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

HistoryIn 1971, Prof.

Leon Chua formulated the

theory of memristors.

In 2008, Stanley

Williams form HP Labs

developed the first stable prototype.

Analogy for a memristorA water pipe where :-

1. Pressure is analogous to voltage 2. Water is analogous to charge 3. Rate of flow of water is analogous to current

If water flows through the pipe in one direction, the diameter of the pipe increases, thus enabling the water to flow faster. If water flows through the pipe in the opposite direction, the diameter of the pipe decreases, thus slowing down the flow of water.

If the water pressure is turned off, the pipe will retain its most recent diameter until the water is turned back on. Similarly a memristor retains its resistance when it is disconnected from supply.

Fabrication:-

Materials used include :- 1. Transition metal oxides like that of Titanium

2. Perovskite oxides

A film of titanium dioxide is sandwiched between two metal electrodes as shown in figure below.

Working:-

Within the titanium oxide film itself, there are 2 layers viz. Doped and Undoped.

Doped layer has a slight depletion of oxygen atoms.

Oxygen vacancies in doped region act as positive charge carriers.

Doped region has lesser resistance than undoped region.

Oxygen vacancies drift in electric field changing the boundary between high resistance(Undoped) and low resistance layers(Doped).

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

Relative lengths of doped and undoped layers contribute to total resistance.

R(off) = High resistance/whole length of film undoped

R(on) = Low resistance/whole length of film doped

Expression for memristance:-

where M(q) = Memristance of a device as a function of charge

Roff = High resistance state Ron = Low resistance state

µv = Mobility of charge

q(t) = Charge flowing thorough device at any time t D = Thickness of semiconductor film sandwiched

between two metal contacts

Benefits of using a memristor:-

the energy it would take to store or retrieve a bit of information is just a hundredth of that in existing flash memory.

flash memory devices switch at 10,000 nanoseconds while as memristors switch at 90ns or even lower.

So, significantly faster than the existing flash memory.Combines the jobs of working memory and hard drives into one tiny device.

Would allow for a quicker boot up since information is not lost when the device is turned off.

Memory devices built using memristors have greater data density . 100 gigabits within a square centimetre

Less power consumption

Applications:-

Replacement of flash memory and better mass storagedevices

Replacement of DRAM which is slow, energy consuming and volatile as well

In nanoelectronic chips it can facilitate use of lesser number of other circuit elements with added functions

In combination with meminductors and memcapacitors,It can be used in remote sensing applications

DRAM

Mass storage devices

END Thank You

Any questions?