Memristor -The fourth fundumental circuit element
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The document presents information about memristors, which are described as semiconductor devices whose resistance depends on the amount of charge that has passed through. It discusses the history of memristors, first theorized in 1971 as the fourth fundamental circuit element. The document outlines the construction and working of TiO2-based memristors, how oxygen vacancies allow the resistance to change based on applied current. Applications include non-volatile memory, neural networks, and analog computing. While promising, memristors still need improvements in defects and standardization before being perfected.
Memristor -The fourth fundumental circuit element
- 1. Seminar Presentation on MEMRISTOR “The Fourth Basic Circuit Element” By- Helal Uddin Mullah Mtech 2nd Semester MTV/EC13/05 [email protected]
- 2. Contents What is Memristor? History Theory Construction & Working An analogy Properties Applications Advantages Conclusion References 2
- 3. WHAT IS MEMRISTOR? • A memristor is a semiconductor whose resistance varies as a function of flux and current. This allows it to “remember” what has passed through the circuit. • It is the fourth fundamental circuit element. • Two terminal device. • Its resistance depends on the amount of charge passed through it. • That’s why it is called “memristor”(memory resistor). 3 Memristor
- 4. Memristance • Memristance is simply charge-dependent resistance. • Unit - ohm (Ω) • Symbol V(t) = M(q(t))*I(t)
- 5. Emergence Of Memristic Theory • Theory was developed in 1971 by Professor Leon Chua at University of California, Berkeley. • Found while exploring symmetry between the three fundamental passive linear circuit elements. • In 2006, R.Stanley Williams developed practical model.
- 7. Three Fundamental Circuit Elements Resistor v R i Capacitor q C v Inductor L i Resistor Georg Ohm 1827 Capacitor von Kleist 1745 Inductor Michael Faraday 1831
- 8. Symmetry Of Relationships Memristors Φ=Mq Voltage (V) Current(i) Charge (q) Flux (Φ) Φ = Li Inductors v=dΦ/dt i=dq/dt Resistors v=Ri q=CvCapacitors
- 10. Working of TiO2 Based Memristor Pt TiTiOv(2-x) TiO2 3 nm 2 nm dopeddepleted (-)ve (+)ve The HP device is composed of a thin (50 nm) titanium dioxide film between two 5 nm thick electrodes, one Ti, the other Pt. Initially, there are two layers to the titanium dioxide film, one of which has a slight doped of oxygen atoms. The oxygen vacancies act as charge carriers, meaning that the doped layer has a much lower resistance than the non- depleted layer. When an electric field is applied, the oxygen vacancies drift ,changing the boundary between the high-resistance and low-resistance layers.
- 11. Thus the resistance of the film as a whole is dependent on how much charge has been passed through it in a particular direction, which is reversible by changing the direction of current. Memristance is displayed only when both the doped and depleted layers contribute to resistance. At a point of time, when enough charge will flow in the film, no ion will be moving then the device enters in to saturation and gives a constant value of M(q) and remains fixed until we reverse the direction of current flow. In this TiO2 Memristor model, for RON<<ROFF The memristance is Where μv = mobility of dopant D= thickness of the film. Equivalent Circuit.
- 12. • Retain its resistance level even after power had been shut down. • Remember (or recall) the last resistance it had, before being shut off. • By changing the speed and strength of the current, it is possible to change the behavior of the device. • A fast and hard current causes it to act as a digital device. • A soft and slow current causes it to act as an analog device. Property Of Memristor
- 13. Applications As a switch As a non volatile memory Can perform logic operations In artificial neural networks 13 1 cm3 of memristor = 1 terabit
- 14. Benefits Of Memristor Technology • Would allow for a quicker boot up since information is not lost when the device is turned off. • Uses less power and produces less heat. • Eliminates the need to write computer programs that replicate small parts of the brain. • Density allows for more information to be stored. • Provides greater resiliency and reliability when power is interrupted in data centers. • Creating a Analog Computer that works much faster than Digital ones. • Conventional devices use only 0 and 1; Memristor can use anything between 0 and 1. • Faster than Flash memory. Allow digital cameras to take pictures with no delay in between. • Compatible with current CMOS interfaces.
- 15. Not Perfect Yet ! • Though hundreds of thousands of memristor semiconductors have already been built, there is still much more to be perfected. • Needs more defect engineering. • No design standards (rules).
- 16. Conclusion In April 2010, HP labs announced that they had practical memristors working at 1 ns (~1 GHz) switching times and 3 nm by 3 nm sizes, which bodes well for the future of the technology.At these densities it could easily rival the current sub-25 nm flash memory technology. So,it is sure that Memristor will change circuit design in the 21st century as radically as the transistor changed it in the 20th. As scientist are saying that Moore’s law is going to be saturated by 2022, we will now have memristors as alternative to transistors. Finally as Leon O Chua mentioned “It’s time to rewrite all the EE textbooks”
- 17. References • L. O. Chua, “Memristor-the missing circuit element,” IEEE Trans. Circuit Theory, vol. 18,pp. 507 -519, Sep. 1971. • D. B. Strukov, G. S. Snider, D. R. Stewart, and R. S. Williams, “The missing memristor found.," Nature, vol. 453, no. 7191, pp. 80 -83, 2008. • M. Di Ventra, Yu. V. Pershin, L. O. Chua, “Circuit elements with memory: memristors, memcapacitors and meminductors”. 2009. arXiv:0901.3682. • L. O. Chua, “Resistance switching memories are memristors," Appl. Phys. A, vol. 102,pp. 765-783, 2011. • http://en.wikipedia.org/wiki/Memristor 17