1. Introduction...................................................................................................................................1

2. Memristor features.......................................................................................................................2

3. Physics of the device......................................................................................................................4

4. History...........................................................................................................................................5

5. HP’s first step.................................................................................................................................7

6. How memristor works???..............................................................................................................8

7. Transistor versus memristor........................................................................................................10

8. Applications.................................................................................................................................12

Non-volatile Memory...................................................................................................................12

Logic/Computation......................................................................................................................12

Neuromorphic Electronics...........................................................................................................12

Signal processing with memristors, Arithmetic processing with memristors, Pattern comparison with memristors, Memristors and artificial intelligence, Memristors and robotics.........................13

9. Materials......................................................................................................................................13

Metallization Cell.........................................................................................................................13

Molecular/Polymer......................................................................................................................13

10. Manufacturing.....................................................................................................................13

11. Benefits of Memristor..............................................................................................................14

12. Major challenges.....................................................................................................................15

13. Future..................................................................................................................................15

14. Conclusion...........................................................................................................................16

15. References...........................................................................................................................17

MEMRISTOR the fourth fundamental electronic element 2010

MEMRISTOR “the fourth fundamental electronic element”

1. Introduction For nearly 150 years, the known fundamental passive circuit elements were limited to the

capacitor (discovered in 1745), the resistor (1827), and the inductor (1831). Anyone familiar with electronics knows the trinity of fundamental components: the resistor, the capacitor, and the inductor. Typically 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, transistors, etc. which are the basic components necessary for electronics to function. Such basic components are fairly limited in number and each has their own characteristic function. For example, resistors perform the function of electrical energy dissipation, capacitors perform the function of electrical energy storage, and transistors perform the functions of electrical energy amplification and switching. The arrangement of these few fundamental circuit components form the basis of almost all of the electronic devices we use in our everyday life.

In a brilliant but underappreciated 1971 paper, Leon Chua, a professor of electrical engi -neering at the University of California, Berkeley, predicted the existence of a fourth fundamental device, which he called a memristor. He proved that memristor behavior could not be duplicated by any circuit built using only the other three elements, which is why the memristor is truly fundamental. Memristor is a contraction of “memory resistor,” because that is exactly its function: to remember its history.

2. 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 1: An atomic force microscope image shows 17 memristors sandwiched between a single bottom wire’ that makes contact with one side of the device and a top wire that contacts the’ opposite side. The wires here are 50-nm wide.

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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, 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.

Fig2: 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

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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 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. 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 graph comparing current and voltage results in a straight line. However, for memristors a similar graph is a little more complicated.

Fig 3: Current voltage characteristic of resistor and memristor

3. Physics of the device

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Fig 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). If M(q(t)) is significant, however, the equation is not equivalent because q(t) and M(q(t)) will vary with time. 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 charge does not vary. 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 resistor. If M(q(t)) increases rapidly, however, current and power consumption will quickly stop. Furthermore, the memristor is static if no current is applied. If I(t) = 0, we find V(t) = 0 and M(t) is constant. This is the essence of the memory effect.

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4. 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 5: Diagram describing the relation between charge, current, voltage and magnetic flux to one another

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 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.

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5. 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. 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.

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 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 the direction of current.[6] Since the HP device displays fast ion conduction at nanoscale, it is considered a nanoionic device

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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. In October 2011, the same team announced the commercial availability of memristor technology within 18 months, as a replacement for Flash, SSD, DRAM and SRAM. In March 2012, a team of researchers from HRL Laboratories and the University of Michigan announced the first functioning memristor array built on a CMOS chip for applications in neuromorphic computer architectures.

6. How memristor works??? 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 6: figure showing crossbar architecture and magnified memristive switch having platinum electrodes and 2 layers of TiO2.

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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.

Fig 7: (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.

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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 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 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.

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 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.

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.

7. 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

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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.

Transistor Memristor 3-terminal switching device with an

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 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. Because they are made of a non-metal it is much harder 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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8. Applications The three main areas of application currently under development for memristor electronics are non-volatile memory, logic/computation, and Neuromorphics.

Non-volatile MemoryNon-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.

Logic/ComputationThe 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.

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.

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Other applications

Signal processing with memristors, Arithmetic processing with memristors, Pattern comparison with memristors, Memristors and artificial intelligence, Memristors and robotics.

9. 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.

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.

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.

Molecular/PolymerMolecular 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.

10. 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

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

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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.

Fig 8: Schematic of our fabrication approach. The cross-shaped trenches are patterned by one NIL step and RIE in resists. After depositing the 3 layers, a liftoff process concludes the fabrication.

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 based 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.

Fig 9: Images of a 1 × 21 array of memristors fabricated using one NIL step. (a) Optical microscope image. (b) SEM image of the junction area. (c) AFM image of part of the array. The junction area is 100 × 100 nm2.

11. 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.

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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.

12. 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.

Dissipates heat when being written to or read.

No design standards (rules).

Needs more defect engineering.

13. Future 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.

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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.

14. Conclusion 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. Memristor will change circuit design in the 21st century as radically as the transistor changed it in the 20th. Don’t forget that the transistor was lounging around as a mainly academic curiosity for a decade until 1956, when a killer app—the hearing aid—brought it into the marketplace. My guess is that the real killer application for memristors will be invented by a curious student who is now just deciding what EE courses to take next year.

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15.References IEEE Spectrum: The Mysterious Memristor By Sally Adee

http://www.spectrum.ieee.org/may08/6207 Memristors Ready For Prime Time R. Colin Johnson URL:

http://www.eetimes.com/showArticle.jhtml?articleID=208803176 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. 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 http://newsvote.bbc.co.uk/mpapps/pagetools/email/news.bbc.co.uk/2/hi/technology/

7377063.stm http://hubpages.com/topics/technology/5338 http://totallyexplained.com/ A hybrid nanomemristor/transistor logic circuit capable of self-programming Julien

Borghetti, Zhiyong Li, Joseph Straznicky, Xuema Li, Douglas A. A. Ohlberg, Wei Wu, Duncan R. Stewart,and R. Stanley Williams1

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