Ketan Singh Seminar Report on Memristor

8/10/2019 Ketan Singh Seminar Report on Memristor

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SEMINAR REPORTON

MEMRISTOR

Submitted for the partial fulfillment of awardof

Degree of Bachelors of Technology(Electrical Engineering)

BY: - KETAN SINGH

(ROLL NO: -1113220022)

Department of Electrical EngineeringG.N.I.O.T. GREATER NOIDA

Session 2013-2014


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CERTIFICATE

This is to certify that KETAN SINGH (1113220022) of E.E. Third

Year have submitted their seminar report on Memristorunder the

guidance of Electrical Engineering Department. This seminar

report is partial fulfillment of their B.Tech course from Uttar Pradesh

Technical University, Lucknow.

Mr. PRADEEP BHARDWAJ

(SEMINAR GUIDE)


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ACKNOWLEDGEMENT

We would like to express our immense gratitude to all those who have

directly or indirectly helped us in completing our seminar onMemristor. I would like to thank themfor their effective guidance

& kind cooperation without which we would not have been able to

introduce a good presentation and complete this seminar report.

We would like to thank the faculty members of Department ofElectrical Engineering for their permission grant, constant

reminders and much needed motivation, which helped us to extract

maximum knowledge from the available sources.

Lastly, my sincere thanks to all our friends for their coordination in

completion of this seminar report.

KETAN SINGH

Roll No. : - 1113220022

(E.E. 3RDYear)


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ABSTRACT

Typically electronics has been define three fundamental circuit components-

resistors, inductors and capacitors are used to define four fundamental circuitvariables which are electric current, voltage, charge and magnetic flux.

Resistors are used to relate current to voltage, capacitors to relate voltage to

charge and inductors to relate current to magnetic flux. But there was no

element which could relate charge to magnetic flux. This lead to the idea and

development of memristors. In 1971, Leon Chua reasoned on the grounds of

symmetry that there should be a fourth Fundamental circuit element which

gives the relationship between flux and charge. He named this circuit element

the memristor, which is short for memory resistor. In May 2008, Researchers at

HP Labs published a paper announcing a model for the physical realization ofthe memristor.

Memristor is a concatenation of memory resistors. The most notable

property of a memristor is that it can save its electronic state even when the

current is turned off, making it a great candidate to replace today's flash

memory. An outstanding feature is its ability to remember a range of electrical

states rather than the simplistic "on" and "off" states that today's digital

processors recognize. Memristor-based computers could be capable of far more

complex tasks. It is proposed that memory storage devices that has very high

data density and computers that require no time for boot up can be developedusing memristor based hardware. A new physical quantity which is also

introduced associated with memristor. It also solves some unexplained voltage

current characteristics observed in certain materials at atomic levels.

HP has already started produced an oxygen depleted titanium memristor.

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TABLE OF CONTENT

CHAPTER NO. TITLE PAGE

1.

2.

3.4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

LIST OF FIGURE

INTRODUCTION

HISTORY.

ADVENT OF HP LABS..

MEMRISTOR THEORY

MEMRISTOR AND RESISTOR

MEMRISTOR VS TRANSISTOR..

APPEARANCE OF MEMRISTOR

MEMRISTOR OPERATION..

PIPE AND CURRENT ANALOGY

APPLICATION.

BENEFITS OF MEMRISTOR

FUTURE.

CONCLUSION..

BIBLIOGRAPHY..

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1

3

57

12

13

15

16

18

20

23

24

25

26

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LIST OF FIGURE

FIGURE

NO.

FIGURE NAME PAGE

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

ABOUT FOUR BASIC CIRCUIT ELEMENTS

ABOUT THE THREE FUNDAMENTAL CIRCUIT

ELEMENTS

SYMBOL OF THE MEMRISTOR

ABOUT V-I CHARACTERISTICS OF A MEMRISTOR

HYSTERESIS MODEL OF RESISTANCE VS. VOLTAGE

CURRENT VOLTAGE CHARACTERISTIC OF RESISTOR

AND MEMRISTOR

CROSSBAR ARRAY STRUCTURE

MOVEMENT OF OXYGEN DEFICIENCY

DIAGRAM OF PIPE AND CURRENT EXAMPLE

NEURAL NETWORKS

FLEXIBLE MEMORY

3

7

8

11

11

12

15

16

18

21

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Generally when most people think about electronics, they may initially think of

products such as cell phones, radios, laptop computers, etc. others, having some

engineering background, may think of resistors, capacitors, etc. which are the

basic components necessary for electronics to function. Such basic components

are fairly limited in number and each having their own characteristic function.

Memristortheory was formulated and named by Leon Chua in a 1971

paper. Chua strongly believed that a fourth device existed to provide conceptual

symmetry with the resistor, inductor, and capacitor. This symmetry follows

from the description of basic passive circuit elements as defined by a relation

between two of the four fundamental circuit variables. A device linking charge

and flux (they defined as time integrals of current and voltage), which would be

the Memristor, was still hypothetical at the time. However, it would not be until

thirty-seven years later, on April 30, 2008, that a team at HP Labs led by the

scientist R. Stanley Williams would announce the discovery of a switching

Memristor. Based on a thin film of titanium dioxide, it has been presented as an

approximately ideal device.

The reason that the Memristoris radically different from the other fundamentalcircuit elements is that, unlike them, it carries a memory of its past. When you

turn off the voltage to the circuit, the Memristor still remembers how much was

applied before and for how long. That's an effect that can't be duplicated by any

circuit combination of resistors, capacitors, and inductors, which is why the

Memristor qualifies as a fundamental circuit element.

1 INTRODUCTION

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The arrangement of these few fundamental circuit components form the

basis of almost all of the electronic devices we use in our everyday life. Thus

the discovery of a brand new fundamental circuit element is something not to be

taken lightly and has the potential to open the door to a brand new type of

electronics. HP already has plans to implement Memristors in a new type of

non-volatile memory which could eventually replace flash and other memory

systems.

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The story of the memristor is truly one for the history books. When Leon Chua,now an IEEE Fellow, wrote his seminal paper predicting the memristor, he was

a newly minted and rapidly rising professor at UC Berkeley. Chua had been

fighting for years against what he considered the arbitrary restriction of

electronic circuit theory to linear systems. He was convinced that nonlinear

electronics had much more potential than the linear circuits that dominate

electronics technology to this day.

Memristance was first predicted by Professor Leon Chua in his paper

Memristor. The missing circuit element published in the IEEE Transactions on

Circuits Theory (1971). In that paper, Prof. Chua proved a number of theorems

to show that there was a 'missing' two terminal circuit element from the family

of "fundamental" passive devices: resistors (which provide static resistance tothe flow of electrical charge), capacitors (which store charges), and inductors

(which resist changes to the flow of charge), or elements that do not add

energy to a circuit. He showed that no combination of resistors, capacitors, and

inductors could duplicate the properties of a memristor. This inability to

duplicate the properties of a memristor with the other passive circuit elements iswhat makes the memristor fundamental. However, this original paper requires a

considerable effort for a non-expert to follow. In a later paper, Prof. Chua

introduced his 'periodic table' of circuit elements.

Fig 1: Diagram describing the relation between charge, current, voltage and magnetic

flux to one another

2 HISTORY

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The pair wise mathematical equations that relate the four circuit quantities-charge, current, voltage, and magnetic flux to one another. These can be related

in six ways. Two are connected through the basic physical laws of electricity

and magnetism, and three are related by the known circuit elements: resistors

connect voltage and current, inductors connect flux and current, and capacitorsconnect voltage and charge. But one equation is missing from this group: therelationship between charge moving through a circuit and the magnetic flux

surrounded by that circuit. That is what memristor, connecting charge and flux.

Even before Chua had his eureka moment, however, many researchers

were reporting what they called anomalous current-voltage behavior in the

micrometer-scale devices they had built out of unconventional materials, likepolymers and metal oxides. But the idiosyncrasies were usually ascribed to

some mystery electrochemical reaction, electrical breakdown, or other spurious

phenomenon attributed to the high voltages that researchers were applying to

their devices.

Leons discovery is similar to that of the Russian chemist Dmitri

Mendeleev who created and used a periodic table in 1869 to find many

unknown properties and missing elements.

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Even though Memristance was first predicted by Professor Leon Chua,

Unfortunately, neither he nor the rest of the engineering community could come

up with a physical manifestation that matched his mathematical expression.

Thirty-seven years later, a group of scientists from HP Labs has finally

built real working memristors, thus adding a fourth basic circuit element to

electrical circuit theory, one that will join the three better-known ones: thecapacitor, resistor and the inductor.

Interest in the memristor revived in 2008 when an experimental solid

state version was reported by R. Stanley Williams of Hewlett Packard. HP

researchers built their memristor when they were trying to develop molecule-sized switches in Teramac (tera-operation-persecond multiarchitecture

computer). Teramac architecture was the crossbar, which has since become the

de facto standard for nanoscale circuits because of its simplicity, adaptability,

and redundancy.

A solid-state device could not be constructed until the unusual behavior

of nanoscale materials was better understood. The device neither uses magneticflux as the theoretical memristor suggested, nor do stores charge as a capacitor

does, but instead achieves a resistance dependent on the history of current using

a chemical mechanism.

The HP teams memristor design consisted of two sets of 21 parallel 40-

nm-wide wires crossing over each other to form a crossbar array, fabricated

using nano imprint lithography. A 20-nm-thick layer of the semiconductor

titanium dioxide (TiO2) was sandwiched between the horizontal and vertical

nanowires, forming a memristor at the intersection of each wire pair. An arrayof field effect transistors surrounded the memristor crossbar array, and thememristors and transistors were connected to each other through metal traces.

The crossbar is an array of perpendicular wires. Anywhere two wires

cross, they are connected by a switch. To connect a horizontal wire to a vertical

wire at any point on the grid, you must close the switch between them. Note that

a crossbar array is basically a storage system, with an open switch representing

a zero and a closed switch representing a one. You read the data by probing the

switch with a small voltage. Because of their simplicity, crossbar arrays have a

3 ADVENT OF HP LABS

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much higher density of switches than a comparable integrated circuit based ontransistors.

Stanley Williams found an ideal memristor in titanium dioxide the stuff

of white paint and sunscreen. In TiO2, the dopants don't stay stationary in a highelectric field; they tend to drift in the direction of the current. Titanium dioxide

oxygen atoms are negatively charged ions and its electrical field is huge. This

lets oxygen ions move and change the materials conductivity, a necessity for

memristors.

The researchers then sandwiched two thin titanium dioxide layers between

two 5 nm thick electrodes. Applying a small electrical current causes the atoms

to move around and quickly switch the material from conductive to resistive,

which enables memristor functionality.

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 thedirection of current. Since the HP device displays fast ion conduction at

nanoscale, it is considered a nanoionic device In the process, the device uses

little energy and generates only small amounts of heat. Also, when the device

shuts down, the oxygen atoms stay put, retaining their state and the data they

represent.

On April 30, 2008, the Hewlett-Packard research team proudly announced

their realization of a memristor prototype.

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Origin of the Memristor :-

There are four fundamental circuit variables in circuit theory. They are

current, voltage, charge and flux. There are six possible combinations of the

four fundamental circuit variables. We have a good understanding of five of

the possible six combinations. The three basic two-terminal devices of

circuit theory namely, the resistor, the capacitor and the inductor are defined

in terms of the relation between two of the four fundamental circuit

variables. A resistor is defined by the relationship between voltage andcurrent, the capacitor is defined by the relationship between charge and

voltage and the inductor is defined by the relationship between flux and

current. In addition, the current is defined as the time derivative of the

charge and according to Faradays law the voltage is defined as the time

derivative of the flux. These relations are shown in Fig. 2

Fig.2: The three circuit elements defined as a relation between four circuit variables

4 MEMRISTOR THEORY

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Definition of a Memristor :-

Memristor, the contraction of memory resistor, is a passive device that

provides a functional relation between charge and flux. It is defined as a

two-terminal circuit element in which the flux between the two terminals isa function of the amount of electric charge that has passed through the

device. Memristor is not an energy storage element. Fig. 3 shows the

symbol for a memristor.

Fig.3: Symbol of the memristor

A memristor is said to be charge-controlled if the relation between flux and

charge is expressed as a function of electric charge and it is said to be flux-

controlled if the relation between flux and charge is expressed as a function

of the flux linkage.

What is Memristance?

Memristance is a property of the memristor. When charge flows in adirection through a circuit, the resistance of the memristor increases. When

it flows in the opposite direction, the resistance of the memristor decreases.

If the applied voltage is turned off, thus stopping the flow of charge, the

memristor remembers the last resistance that it had. When the flow of

charge is started again, the resistance of the circuit will be what it waswhen it was last active.

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The memristor is essentially a two-terminal variable resistor, withresistance dependent upon the amount of charge q that has passed between

the terminals.

To relate the memristor to the resistor, capacitor, and inductor, it is helpful

to isolate the term M(q), which characterizes the device, and write it as adifferential equation:

Where Q is defined by =

and is defined by =

The variable ("magnetic flux linkage") is generalized from the circuit

characteristic of an inductor. The symbol may simply be regarded as the

integral of voltage over time.

Thus, the memristor is formally defined as a two-terminal element in which

the flux linkage (or integral of voltage) between the terminals is a

function of the amount of electric charge Q that has passed through the

device. Each memristor is characterized by its memristance function

describing the charge-dependent rate of change of flux with charge.

Substituting that the flux is simply the time integral of the voltage, and

charge is the time integral of current, we may write the more convenient

form

It can be inferred from this that memristance is simply charge-dependent

resistance. If M(q(t)) is a constant, then we obtain Ohm's law

R(t) = V(t)/ I(t).However, the equation is not equivalent because q(t) and

M(q(t)) will vary with time.

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Solving for voltage as a function of time we obtain

This equation reveals that memristance defines a linear relationship

between current and voltage, as long as M does not vary with charge.

Furthermore, the memristor is static if no current is applied. If I(t) = 0, wefind V(t) = 0 and M(t) is constant. This is the essence of the memory

effect.

The power consumption characteristic recalls that of a resistor, I2R

As long as M(q(t)) varies little, such as under alternating current, the

memristor will appear as a constant resistor.

Properties of a Memristor

CurrentVoltage Curve of a Memristor

An important fingerprint of a memristor is the pinched hysteresis

loop current voltage characteristic. For a memristor excited by a

periodic signal, when the voltage v(t) is zero, the current i(t) is also

zero and vice versa. Thus, both voltage v(t) and current i(t) have

identical zero-crossing. Another signature of the memristor is thatthe pinched hysteresis loop shrinks with the increase in the

excitation frequency. Figure 4 shows the pinched hysteresis loop

and an example of the loop shrinking with the increase in

frequency. In fact, when the excitation frequency increases towardsinfinity, the memristor behaves as a normal resistor.

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Fig. 4: The pinched hysteresis loop and the loop shrinking with the increase in

frequency

HYSTERESIS MODEL

Hysteresis model illustrates an idealized resistance behavior

demonstrated in accordance with above current-voltage

characteristic wherein the linear regions correspond to a relatively

high resistance (RH) and low resistance (RL) and the transition

regions are represented by straight lines.

Fig 5: Idealized hysteresis model of resistance vs. voltage for memristance switch.

Thus for voltages within a threshold region (-VL2


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This new circuit element shares many of the properties of resistors and sharesthe same unit of measurement (ohms). However, in contrast to ordinary

resistors, in which the resistance is permanently fixed, memristance may be

programmed or switched to different resistance states based on the history of the

voltage applied to the memristance material. This phenomena can be understood

graphically in terms of the relationship between the current flowing through a

memristor and the voltage applied across the memristor. In ordinary resistors

there is a linear relationship between current and voltage so that a graphcomparing current and voltage results in a straight line. However, for

memristors a similar graph is a little more complicated.

Fig 6: Current voltage characteristic of resistor and memristor

5 MEMRISTOR AND RESISTOR

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The first transistor was a couple of inches across which was developed about 60years ago. Today, a typical laptop computer uses a processor chip that contains

over a billion transistors, each one with electrodes separated by less than 50 nm

of silicon. This is more than a 1000 times smaller than the diameter of a human

hair. These billions of transistors are made by top down methods that involve

depositing thin layers of materials, patterning nano-scale stencils and effectively

carving away the unwanted bits. This approach has become overly successful.

The end result is billions of individual components on a single chip, essentiallyall working perfectly and continuously for years on end. No other manufactured

technology comes close in reliability or cost.

Still, miniaturization cannot go on forever, because of the basic properties

of matter. We are already beginning to run into the problem that the siliconsemiconductor, copper wiring and oxide insulating layers in these devices are

all made out of atoms. Each atom is about 0.3 nm across.

The entire body of the transistor is being doped less consistently

throughout as its sizes are reduced below the nanometers which make thetransistor more unpredictable in nature. It will be more difficult and costly to

press forward additional research and equipment involving these unpredictablebehaviors as they occur. Therefore the electronic designs will have to replace

their transistors to the memristors which are not steadily infinitesimal, but

increasingly capable.

The memristor is very likely to follow the similar steps of how the

transistor was implemented in our electronic systems. They may argue that the

transistor took approximately sixty years to reach the extent of todays research

and capabilities. Therefore, the memristors may take approximately just as long

to actually create some of its promising potentials such as artificial intelligence.This new advancement means more jobs for research and development andmore potential for inventions and designs. Also, the dependency on getting the

transistors to work efficiently in atom sized is lessened.

6 MEMRISTOR VS TRANSISTOR

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Transistor Memristor

3-terminal switching device withan input electrode (e.g. source),

an output electrode (e.g. drain),and a control electrode (e.g. gate).

Requires a power source to retaina data state.

Stores data by electron charge.

Scalable by reducing the laterallength and width dimensions

between the input and outputelectrodes.

Capable of performing analog ordigital electronic functions

depending on applied bias

voltages.

Fabrication requires opticallithography.

2-terminal device with one of theelectrodes acting either as a

control electrode or a sourceelectrode depending on the

voltage magnitude.

Does not require a power sourceto retain a data state.

Stores data by resistance state.

Scalable by reducing the

thickness of the memristormaterials.

Capable of performing analog ordigital electronic functions

depending on particular material

used for memristor.

Fabrication by optical lithographybut alternative (potentially

cheaper) mass productiontechniques such as nano imprint

lithography and self assemblyhave also been implemented

Another reason for incorporating memristors is the materials used to make each

element. Transistors are usually made of silicon, a non-metal. While this has

proven to be a very reliable source, it returns to the problem of transistors

needing to become smaller. Because they are made of a non-metal it is muchharder to make them much smaller. Memristors, on the other hand, are made of

titanium oxide. Titanium is a metal which is much easier to make into smaller

size. Since memristors have twelve times the power of transistors, however,

products can be made smaller and more powerful without reducing the size of

the product that powers them.

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HP Labs' memristor has Crossbar type memristive circuits contain a lattice of40-50nm wide by 2-3nm thick platinum wires that are laid on top of one another

perpendicular top to bottom and parallel of one another side to side. The top and

bottom layer are separated by a switching element approximately 3-30nm in

thickness. The switching element consists of two equal parts of titanium dioxide

(TiO2). The layer connected to the bottom platinum wire is initially perfect

TiO2 and the other half is an oxygen deficient layer of TiO2 represented by

TiO2-x where x represents the amount of oxygen deficiencies or vacancies. Theentire circuit and mechanism cannot be seen by the naked eye and must be

viewed under a scanning tunneling microscope, as seen in Figure 6, in order to

visualize the physical set up of the crossbar design of the memristive circuit

described in this section.

Fig 7: figure showing crossbar architecture and magnified memristive switch having

platinum electrodes and 2 layers of TiO2

7 APPEARANCE OF MEMRISTOR

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The memristors operation as a switch can be explained in three steps. These

first of these steps is the application of power or more importantly current to thememristor. The second step consists of the amount of time that the current flows

across the crossbar gap and how the titanium cube converts from a semi-conductor to a conductor. The final step is the actual memory of the cube that

can be read as data.

STEP 1:-

As explained above, each gap that connects two platinum wires contains a

mixture of two titanium oxide layers. The initial state of the mixture is halfwaybetween conductance and semi-conductance. Two wires are selected to applypower to in either a positive or negative direction. A positive direction will

attempt to close the switch and a negative direction will attempt to open the

switch. The application of this power will be able to completely open the circuit

between the wires but it will not be able to completely close the circuit since the

material is still a semi-conductor by nature. Power can be selectively placed on

certain wires to open and close the switches in the memristor.

Fig 8: TiO2-x layer having oxygen deficiencies over insulating TiO2 layer. (b) Positive

voltage applied to top layer repels oxygen deficiencies in to the insulating TiO2 layer

below. (c) Negative voltage on the switch attracts the positively charged oxygen bubbles

pulling them out of the TiO2.

8 MEMRISTOR OPERATION

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STEP 2:-

The second step involves a process that takes place at the atom level and is notvisible by any means. It involves the atomic process that the gap material, made

from titanium dioxide, goes through that opens and closes the switch. The initialstate of the gap is neutral meaning that it consists of one half of pure titanium

dioxide TiO2 and one half of oxygen starved titanium dioxide TiO2-x where x

in the initial state is 0.05. As positive current is applied, the positively charged

oxygen vacancies push their way into the pure TiO2 causing the resistance in

the gap material to drop, becoming more conductive, and the current to rise.

Inversely, as a negative current is applied the oxygen vacancies withdraw from

the pure TiO2 and condense in the TiO2-x half of the gap material causing the

pure and more resistive TiO2 to have a greater ratio slowing the current in the

circuit. When the current is raised the switch is considered open (HI) and fordata purposes a binary 1. As current is reversed and the current is dropped theswitch is considered closed (LOW) or a binary 0 for data purposes.

STEP 3:-

Step three explains the final step of memristance and is the actual step that

makes the circuit memristive in nature. As explained previously, the concept of

memristance is a resistor that can remember what current passed through it.

When power is no longer applied to the circuit switches, the oxygen vacanciesremain in the position that they were last before the power was shut down. This

means that the value of the resistance of the material gap will remain until

indefinitely until power is applied again. This is the true meaning of

memristance. With an insignificant test voltage, one that wont affect themovement of molecules in the material gap will allow the state of the switches

to be read as data. This means that the memristor circuits are in fact storing data

physically.

If we want a positive voltage to turn the memristor off, then we want the

titanium oxide layer with vacancies on the top layer. But if you want a positive

voltage to turn the memristor on, then you need the layers reversed. In its initial

state, a crossbar memory has only open switches, and no information is stored.

But once you start closing switches, you can store vast amounts of information

compactly and efficiently.

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A common analogy to describe a memristor is similar to that of a resistor. Think

of a resistor as a pipe through which water flows. The water is electric charge.The resistors obstruction of the flow of charge is comparable to the diameter of

the pipe: the narrower the pipe, the greater the resistance. For the history ofcircuit design, resistors have had a fixed pipe diameter. But a memristor is a

pipe that changes diameter with the amount and direction of water that flows

through it. If water flows through this pipe in one direction, it expands

(becoming less resistive). But send the water in the opposite direction and the

pipe shrinks (becoming more resistive). Further, the memristor remembers its

diameter when water last went through. Turn off the flow and the diameter of

the pipe freezes until the water is turned back on. , the pipe will retain it mostrecent diameter until the water is turned back on. Thus, the pipe does not store

water like a bucket (or a capacitor) it remembers how much water flowed

through it.

Fig 9 .Schematic diagram of pipe and current example

The reason that the memristor is radically different from the other fundamentalcircuit elements is that, unlike them, it carries a memory of its past. When you

turn off the voltage to the circuit, the memristor still remembers how much wasapplied before and for how long. That's an effect that can't be duplicated by any

9 PIPE AND CURRENT ANALOGY

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circuit combination of resistors, capacitors, and inductors, which is why thememristor qualifies as a fundamental circuit element. Technically such a

mechanism can be replicated using transistors and capacitors, but, it takes a lot

of transistors and capacitors to do the job of a single memristor.

Memristance is measured by the electrical component memristor. The waya resistor measures resistance, a conductor measures conduction, and an

inductor measures inductance, a memristor measures memristance. An ideal

memristor is a passive two-terminal electronic device that expresses only

memristance. However it is difficult to build a pure memristor, since every real

device contains a small amount of another property.

Two properties of the memristor attracted much attention. Firstly, its

memory characteristic, and, secondly, its nanometer dimensions. The memory

property and latching capability enable us to think about new methods for nano-

computing. With the nanometer scale device provides a very high density and is

less power hungry. In addition, the fabrication process of nano-devices is

simpler and cheaper than the conventional CMOS fabrication, at the cost of

extra device defects.

At the architectural level, a crossbar-based architecture appears to be the

most promising nanotechnology architecture. Inherent defect-tolerance

capability, simplicity, flexibility, scalability, and providing maximum density

are the major advantages of this architecture by using a memristor at each crosspoint.

Memristors are passive elements, meaning they cannot introduce energy

into a circuit. In order to function, memristors need to be integrated into circuitsthat contain active elements, such as transistors, which can amplify or switch

electronic signals. A circuit containing both memristors and transistors could

have the advantage of providing enhanced functionality with fewer components,

in turn minimizing chip area and power consumption.

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NON-VOLATILE MEMORY : -

Non-volatile memory is the dominant area being pursued for memristortechnology. Of course most of the companies listed (with the exception

of Hewlett Packard) do not refer to their memory in terms of the

memristor and rather use a variety of acronyms (i.e. RRAM, CBRAM,

PRAM, etc.) to distinguish their particular memory design. While these

acronyms do represent real distinctions in terms of the materials used or

the mechanism of resistance switching employed, the materials are still

all memristors because they all share the same characteristic voltage-induced resistance switching behavior covered by the mathematical

memristor model of Chua. Flash memory currently dominates the

semiconductor memory market. However, each memory cell of flash

requires at least one transistor meaning that flash design is highly

susceptible to an end to Moores law. On the other hand, memristor

memory design is often based on a crossbar architecture which does not

require transistors in the memory cells. Although transistors are still

necessary for the read/write circuitry, the total number of transistors for a

million memory cells can be on the order of thousands instead of

millions and the potential for addressing trillions of memory cells exists

using only millions (instead of trillions) of transistors. Another

fundamental limitation to conventional memory architectures is VonNeumanns bottleneck which makes it more difficult to locate

information as memory density increases. Memristors offer a way to

overcome this hurdle since they can integrate memory and processing

functions in a common circuit architecture providing a de-segregation

between processing circuitry and data storage circuitry.

LOGIC/COMPUTATION : -

The uses of memristor technology for logic and computational electronicsis less well developed than for memory architectures but the seeds of

innovation in this area are currently being sown. Memristors appear

particularly important to the areas of reconfigurable computing

architectures such as FPGAs in which the arrangement between arrays of

basic logic gates can be altered by reprogramming the wiring

interconnections. Memristors may be ideal to improve the integrationdensity and reconfigurability of such systems. In addition, since some

10 APPLICATIONS

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memristor materials are capable of tunablity in their resistance state theycan provide new types of analog computational systems which may find

uses in modeling probabilistic systems (e.g. weather, stock market, bio

systems) more efficiently than purely binary logic-based processors.

NEUROMORPHIC ELECTRONICS: -

Neuromorphics has been defined in terms of electronic analog circuits

that mimic neurobiological architectures. Since the early papers of Leon

Chua it was noted that the equations of the memristor were closely related

to behavior of neural cells. Since memristors integrate aspects of both

memory storage and signal processing in a similar manner to neural

synapses they may be ideal to create a synthetic electronic system similarto the human brain capable of handling applications such as pattern

recognition and adaptive control of robotics better than what is achievable

with modern computer architectures.

Fig 10: neural networks

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Provides greater resiliency and reliability when power is interrupted in

data centers.

Have great data density.

Combines the jobs of working memory and hard drives into one tiny

device.

Faster and less expensive than MRAM.

Uses less energy and produces less heat.

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

the device is turned off.

Operating outside of 0s and 1s allows it to imitate brain functions.

Does not lose information when turned off.

Has the capacity to remember the charge that flows through it at a given

point in time.

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

between 0 and 1(0.3, 0.8, 0.5, etc.)

Faster than Flash memory.

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.

100 GBs of memory made from memristors on same area of 16 GBs of

flash memory.

High Defect Tolerance allows high defects to still produce high yields

as opposed to one bad transistor which can kill a CPU.

Compatible with current CMOS interfaces.

As non-volatile memory, memristors do not consume power when idle.

3 Memristors to make a NAND gate, 27 NAND gates to make a

Memristor!!!

More magnetic than magnetic disks.

11 BENEFITS OF MEMRISTOR

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Memristor bridges the capability gaps that electronics will face in the near

future according to Moores Law and will replace the transistor as the main

component on integrated circuit (IC) chips.

The possibilities are endless since the memristor provides the gap to

miniaturizing functional computer memory past the physical limit currently

being approached upon by transistor technology.

When is it coming? Researchers say that no real barrier prevents

implementing the memristor in circuitry immediately. But it's up to the businessside to push products through to commercial reality. Memristors made to

replace flash memory (at lower cost and lower power consumption) will likely

appear first; HP's goal is to offer them by 2012. Beyond that, memristors will

likely replace both DRAM and hard disks in the 2014-to-2016 time frame. As

for memristor-based analog computers, that step may take 20-plus years.

Fig 11: Flexible memory

12 FUTURE

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Thus the discovery of a brand new fundamental circuit element is something notto be taken lightly and has the potential to open the door to a brand new type of

electronics. Memristor will change circuit design in the 21st century as radically

as the transistor changed it in the 20th. Note that the transistor was lounging

around as a mainly academic curiosity for a decade until 1956, when a

revolutionary app the hearing aid brought it into the marketplace.

By redesigning certain types of circuits to include Memristors, it is possibleto obtain the same function with fewer components, making the circuit itself

less expensive and significantly decreasing its power consumption. In fact, it

can be hoped to combine Memristors with traditional circuit-design elements to

produce a device that does computation. The Hewlett-Packard (HP) group is

looking at developing a memristor-based nonvolatile memory that could be1000 times faster than magnetic disks and use much less power.

Memristor open door to a wide area of research in the field of computer

hardware and memory storage devices that has much higher data density. As

rightly said by the originators of memristor, Leon Chua and R . Stanley

Williams, Memristors are so significant that it would be mandatory to re-

write the existing electronic engineering textbooks.

13 CONCLUSION

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1. Memristor resistance modulation for analog applications Tsung Wen Lee

and Janice H Nickel IEEE,electron device letters, vol 33,oct ,2012

2. Memristor applications for programmable analog ICs, Sangho Shin and

Kyungmin Kim,IEEE Transactions on nanotechnology, vol 10,2011

3. Compact models for memristors based on charge flux constitutive

relationships, IEEE,2010 IEEE Spectrum: The Mysterious Memristor By

Sally Adee http://www.spectrum.ieee.org/may08/6207

4. Memristors Ready For Prime Time R. Colin Johnson

URL:http://www.eetimes.com/showArticle.jhtml?articleID=208803176

5. Flexible memristor: Memory with a twist Vol. 453, May 1, 2008.

PHYSorg.com

6. L. O. Chua, Memristor The missing circuit element, IEEE Trans. Circuit

Theory, vol. CT-18, pp. 507519, 1971.

7. Memristor - Wikipedia, the free encyclopedia

8. http://www.hpl.hp.com/

9. How We Found the Missing Memristor By R. Stanley Williams,

December 2008 IEEE Spectrum, www.spectrum.ieee.org10. http://avsonline.blogspot.com/

11. http://memristor.pbworks.com/

12. http://4engr.com/

13. http://knol.google.com/

14. http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/

hi/technology/7377063.stm

15. http://hubpages.com/topics/technology/5338

16. http://totallyexplained.com/

14 BIBLIOGRAPHY
http://4engr.com/http://4engr.com/http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/7377http://4engr.com/

Documents

Ketan Singh Seminar Report on Memristor