Memristor documentation prepared by dhana

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CONTENTS
Page no
1. INTRODUCTION 2
2. MEMRISTOR 6
3. MANUFACTURING AND WORKING 11
4. APPLICATIONS AND BENEFITS OF MEMRISTOR 16
5. CONCLUSION AND FUTURE SCOPE 20

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CHAPTER 1
INTRODUCTION
Memristor theory 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
(themselves 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 memristor is radically different from the other fundamental circuit 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.
1.1. Need For Memristor
A memristor is one of four basic electrical circuit components, joining the resistor, capacitor,
and inductor. The memristor, short for "memory resistor" was first theorized by student Leon Chua in
the early 1970s. He developed mathematical equations to represent the memristor, which Chua believed
would balance the functions of the other three types of circuit elements.
The known three fundamental circuit elements as resistor, capacitor and inductor relates four
fundamental circuit variables as electric current, voltage, charge and magnetic flux. In that we were
missing one to relate charge to magnetic flux. That is where the need for the fourth fundamental element
comes in. This element has been named as memristor.
Memristance (Memory + Resistance) is a property of an Electrical Component that describes the
variation in Resistance of a component with the flow of charge. Any two terminal electrical component
that exhibits Memristance is known as a Memristor. Memristance is becoming more relevant and
necessary as we approach smaller circuits, and at some point when we scale into nano electronics, we
would have to take memristance into account in our circuit models to simulate and design electronic
circuits properly.

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An ideal memristor is a passive two-terminal electronic device that is built to express only the property
of memristance (just as a resistor expresses resistance and an inductor expresses inductance).
However, in practice it may be difficult to build a 'pure memristor,' since a real device may
also have a small amount of some other property, such as capacitance (just as any real inductor also
has resistance). A common analogy for a resistor is a pipe that carries water. The water itself is
analogous to electrical charge, the pressure at the input of the pipe is similar to voltage, and the rate
of flow of the water through the pipe is like electrical current. Just as with an electrical resistor, the
flow of water through the pipe is faster if the pipe is shorter and or it has a larger diameter.
1.2. HISTORY
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 to the 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 is what 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.1.1 : Describing the relation between charge, current, voltage and magnetic flux to one
another

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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.
capacitors connect voltage and charge. But one equation is missing from this group: the relationship
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, like polymers 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.
Leon’s 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.
1.2.1. HP’s first step:
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: the capacitor, 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-per-second 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 magnetic flux 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 team’s memristor design consisted of two sets of 21 parallel 40-nm-wide wires crossing
over each other to form a crossbar array, fabricated using nanoimprint lithography.

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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
array of field effect transistors surrounded the memristor crossbar array, and the memristors 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 much higher density of switches
than a comparable integrated circuit based on transistors electrodes.
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 high electric 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 material’s conductivity, a necessity for
memristors.
The researchers then sandwiched two thin titanium dioxide layers between two 5 nm thick
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 the
direction 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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CHAPTER 2
MEMRISTOR
2.1. MEMRISTOR FEATURES:
Memristor is passive two-terminal element that maintains functional relation between charge
flowing through the device (i.e. time integral of current) and flux or A memristor is a two-terminal
semiconductor device whose resistance depends on the magnitude and polarity of the voltage applied to
it and the length of time that voltage has been applied. When you turn off the voltage, the memristor
remembers its most recent resistance until the next time you turn it on, whether that happens a day later
or a year later.
Fig.2.1: An atomic force microscope image shows 17 memristors
As its name implies, the memristor can "remember" how much current has passed through it. And
by alternating the amount of current that passes through it, a memristor can also become a one-element
circuit component with unique properties. Most notably, it can save its electronic state even when the
current is turned off, making it a great candidate to replace today's flash memory 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 resistor’s 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 of circuit
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,

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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 most recent
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.2.2: Schematic diagram of pipe and current example
The reason that the memristor is radically different from the other fundamental circuit 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.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 way a 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.

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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 cross point.
Memristors are passive elements, meaning they cannot introduce energy into a circuit. In order
to function, memristors need to be integrated into circuits that 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.
This new circuit element shares many of the properties of resistors and shares the 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.In ordinary resistors there is a linear relationship
between current and voltage so that a graph comparing current and voltage results in a
straightline. However, for memristors a similar graph is a little more complicated.
Fig.2.3: Current voltage characteristic of resistor and memristor

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2.3. Definition of Memristor
“The memristor is formally defined as a two-terminal 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.”
Chua defined the element as a resistor whose resistance level was based on the amount of charge
that had passed through the memristor.
2.4. MEMRISTANCE
Memristance is a property of an electronic component to retain its resistance level even after power
had been shut down or lets it remember (or recall) the last resistance it had before being shut off.
Fig.2.4: Memristor Symbol
The memristor is formally defined as a two-terminal 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.
Each memristor is characterized by its memristance function describing the charge- dependent rate of
change of flux with charge.
Noting from Faraday's law of induction that magnetic flux is simply the time integral of 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).

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This equation reveals that memristance defines a linear relationship between current and voltage, as long
as charge does not vary. The power consumption characteristic recalls that of a resistor, I2R.

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CHAPTER 3
MANUFACTURINGAND WORKING
3.1.MANUFACTURING
Manufacturers could make memristors in the same chip fabrication plants used now, so
companies would not have to undertake expensive retooling or new construction. And memristors
are by no means hard to fabricate. The titanium dioxide structure can be made in any semiconductor
fab currently in existence. The primary limitation to manufacturing hybrid chips with memristors is that
today only a small number of people on Earth have any idea of how to design circuits containing
memristors.
Fig.3.1: Schematic of our fabrication approach.
One of the key fabrication advantages of the crossbar architecture is that the structure is a well
ordered, periodic and simple structure. However, to achieve Nanoscale resolutions the standard
lithography approaches are insufficient. The manufacturing techniques for the Nanoscale crossbar
devices developed by Hewlett-Packard include nanoimprint lithography, which uses a stamp-like
structure with nanometer resolution to transfer a pattern of Nanoscale resolution to a substrate.
Additional nanoscale fabrication approaches can include self-assembly techniques in which a mixture of
polymers or other materials can form periodic structures on a surface base on processes of energy
minimalization. These self-assembly techniques can be used to form a periodic mask structure over a
metal film which can act as a resist to control removal of metal layers in regions not covered by the
mask resulting in the desired metal nanowires required for the crossbar structure.

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Fig.3.2: Images of a 1 × 21 array of memristors.
(a) Optical microscope image. (b) SEM image of the junction area. (c) AFM image of part of the
array.
3.2. HOW MEMRISTOR WORKS???
3.2.1. Appearance – HP Labs' memristor has Crossbar type memristive circuits contain a lattice of 40-
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. The entire 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.3.3 : Showing crossbar architecture and magnified memristive switch.

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3.2.2. Operation – The memristor’s 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 the memristor. 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 halfway between conductance and semi-
conductance. Two wires are selected to apply power 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.
Step 2 – The second step involves a process that takes place at the atom level and is not visible 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 initial state 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 greater ratio slowing the current in the circuit. When the current is raised the switch is
considered open (HI) and for data purposes a binary 1. As current is reversed and the current is
dropped the switch is considered closed (LOW) or a binary 0 for data purposes.
Fig.3.4 : Diffusing of Oxygen molecules

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(a) 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.
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 resist that can remember
what current passed through it. When power is no longer applied to the circuit switches, the oxygen
vacancies remain 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 won’t affect the movement
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.
3.3. Transistor versus Memristor
The first transistor was a couple of inches across which was developed about 60 years
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, essentially all 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 silicon semiconductor, 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 nanometres which make the transistor more unpredictable in nature. It will be more
difficult and costly to press forward additional research and equipment involving these unpredictable
behaviours as they occur. Therefore the electronic designs will have to replace their transistors to the
memristors which are not steadily infinitesimal, but increasingly capable.

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Table: Difference between Transistor and Memristor:
Transistor Memristor
 3-terminal switching device with an
o input electrode (e.g. source), an
output electrode (e.g. drain),
and a control electrode (e.g.
gate).
 Requires a power source to retain a data
state.
 Stores data by electron charge.
 Scalable by reducing the lateral length
and width dimensions between the input
and output electrodes.
 Capable of performing analog or digital
electronic functions depending on
applied bias voltages.
 Fabrication requires optical lithography.
 2-terminal device with one of the electrodes
o acting either as a control electrode or a
source electrode depending on the voltage
magnitude.
 Does not require a power source to retain a data
state.
 Stores data by resistance state.
 Scalable by reducing the thickness of the
memristor materials.
 Capable of performing analog or digital
electronic functions depending on particular
material used for memristor.
 Fabrication by optical lithography but
alternative (potentially cheaper) mass production
techniques such as nanoimprint lithography and
self assembly have also been implemented
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 today’s 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 and more potential for inventions and
designs. Also, the dependency on getting the transistors to work efficiently in atom sized is lessened.
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.

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CHAPTER 4
APPLICATIONS AND BENEFITS OF MEMRISTOR
4.1. APPLICATIONS:
The three main areas of application currently under development for memristor electronics
are :-
(i) Non-volatile memory
(ii) Logic/computation, and
(iii) Neuromorphics.
4.1.1. Non-volatile Memory:
Non-volatile memory is the dominant area being pursued for memristor technology. 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 Moore’s 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 Von Neumann’s 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.

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4.1.2. Logic/Computation:
The uses of memristor technology for logic and computational electronics is 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 integration
density and reconfigurability of such systems. In addition, since some memristor materials are capable
of tunablity in their resistance state they can 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.
4.1.3. Neuromorphic Electronics :
Neuromorphics has been defined in terms of electronic analog circuits that mimic neuro- biological
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 similar to 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.
4.2. Other applications:
Signal processing with memristors, Arithmetic processing with memristors, Pattern comparison
with memristors, Memristors and artificial intelligence, Memristors and robotics.
4.2.1. Materials:
Although the different memristor materials have their respective merits and possess differences
in terms of their underlying physics each material share the same resistance switching properties
possessed by memristors. Variety of binary oxides such as WO3, Ir2O3, MoO3, ZrO2, and RhO2
adjusted to have memristive properties. A variety of other memristor variations based on TiO, CuO,
NiO, ZrO, and HfO materials have been under experimental investigation for the past several years.
4.2.2. Metallization Cell:
The memristive effect is due to the formation of metallic filaments which interconnect two
electrodes separated by an electrolytic material. The metallic filaments can be broken or reformed
depending on the polarity of an applied voltage.

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4.2.3. Perovskite:
Perovskite materials are based on a variety of ternary oxides including PCMO, SrTiO3, SrZrO3,
and BaTiO3. These types of materials appear to have variable resistances which are more easily
tunable via pulse number modulation which may make these materials more attractive for analog
memristor electronics than the metallization cell or binary oxide materials.
4.2.4. Molecular/Polymer:
Molecular and polymer materials have been investigated by Hewlett-Packard and Advanced
Micro Devices as the basis for new types of non-volatile memory. HP has been working with molecular
systems called rotaxane which are thought to exhibit a resistance switching effect based on a
mechanical reconfiguration of the molecule. AMD has been focusing on ionic molecular and polymer
materials which also produce resistance switching behavior and may have superior analog memristive
properties than other materials.
4.3. BENEFITS OF MEMRISTOR:
 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.

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 High Defect Tolerance allows high defects to still produce high yields as opposed to one bad
transistor which can kill a CPU.
4.4. Major Challenges
 The memristor’s major challenges are its relatively low speeds and the need for designers to
learn how to build circuits with the new element.
 Though hundreds of thousands of memristor semiconductors have already been built, there is
still much more to be perfected.

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5.CONCLUSION AND FUTURE SCOPE
CONCLUSION:
By re-designing certain types of circuits to include memristors, it is possible to 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 be 1000 times faster than magnetic disks
and use much less power.
As rightly said by Leon Chua and R.Stanley Williams (originators of memristor),
memrisrors are so significant that it would be mandatory to re-write the existing electronics
engineering textbooks.
FUTURE SCOPE:
Memristor bridges the capability gaps that electronics will face in the near future according to
Moore’s 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 business side 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.

21. 21
REFERENCES:
1. IEEE Spectrum: The Mysterious Memristor By Sally Adee
http://www.spectrum.ieee.org/may08/6207
2. Memristors Ready For Prime Time R. Colin Johnson URL:
http://www.eetimes.com/showArticle.jhtml?articleID=208803176
3. Flexible memristor: Memory with a twist Vol. 453, May 1, 2008. PHYSorg.com
L. O. Chua, Memristor The missing circuit element, IEEE Trans. Circuit Theory, vol.
CT-18, pp. 507–519, 1971.
4. Memristor - Wikipedia, the free encyclopedia
http://www.hpl.hp.com/
“How We Found the Missing Memristor” By R. Stanley Williams, December 2008 •
IEEE Spectrum, www.spectrum.ieee.org
http://avsonline.blogspot.com/
http://memristor.pbworks.com/
http://4engr.com/
http://knol.google.com/k