MEMRISTORS

PRESENTED BY UNDER THE GUIDANCE OFABHISHEK KUMAR DR. D. K. SRIVASTAVA1104331002

CONTENTS INTRODUCTION WHAT IS A MEMRISTOR BASIC WORKING OF A MEMRISTOR FEATURES OF A MEMRISTOR PIPE AND CURRENT ANALOGY V vs I CURVE THE HP MEMRISTOR MATERIALS USED ADVANTAGES POTENTIAL APPLICATIONS TIMELINE REFERENCES

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). In 1971, Professor LEON CHUA of University of California suggested the existence of a fourth fundamental passive element which related magnetic flux and charge.This missing fourth element was later confirmed to be existing by HP LABS in 2008, and was named a “MEMRISTOR”

THE MISSING ELEMENT…???

Resistor

Capacitor Inductor

Voltage (V)

Current(i)

Charge (q)

Flux (Φ)

v=dΦ/dt i=dq/dt

???

q=Cv Φ = Li

v=Ri

THE FOURTH ELEMENT

WHAT IS A MEMRISTOR

A MEMRISTOR is basically a “MEMORY RESISTOR”

It is a passive two-terminal element that maintains functional relation between charge flowing through the device and flux

BASIC WORKING

It 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 the voltage is turned off, 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.

FEATURES OF A MEMRISTOR

The characteristic of a Memristor is its MEMRISTANCE (M)

Φ = M qIt can remember its last resistance state even if voltage supply is cut off. Hence, it ‘remembers’ its last state.Unit of Memristance is Ω (ohms)

SYMBOL OF A MEMRISTOR

Resistance depends on magnitude, polarity and time application of voltage.

PIPE AND CURRENT ANALOGY

MATHEMATICAL ANALYSIS

Φ = M q

CURRENT-VOLTAGE BEHAVIOUR IN RESISTORS AND MEMRISTORS

THE HP MEMRISTOR

In 2008, after 37 years since the existence of memristor was predicted, a team at HP LABS under the leadership of R. Stanley Williams created the first memristor.

The memristor was constructed with the help of TiO2 and TiO2 –x layers.

Initially, one layer is depleted of oxygen, while the other is abundant of oxygen atoms.

The depleted layer has much lower resistance than the non depleted layer.

WORKING OF HP MEMRISTOR

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.

Two thin titanium dioxide layers are sandwiched 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 the device shuts down, the oxygen atoms stay put, retaining their state and the data they represent.

TiO2-x

TiO2

MATERIALS USED

Oxides such as WO3,Ir2O3,ZrO2 and RhO2

Platinum electrodes Perovskite material (Variable resistance or

tuneable resistance material such as SrTiO3, SrZrO3, and BaTiO3)

Molecular and polymer material- rotaxane which exhibits switchable resistance.

BENEFITS OF MEMRISTORS

Does not lose information when turned off. Have great data density. Combines the jobs of working memory and

hard drives into one tiny device Uses less energy and produces less heat. Allows 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 Faster than Flash memory.

POTENTIAL APPLICATIONS

Can be used in place of Solid State Memories (SSD), providing more speed and using lesser area.

Can be used as non volatile memories instead of DRAM, thus preventing loss of data on power interruption and faster boot.

Can be used in Programmable Logic Arrays (PLA)

Can be used in artificial neural networks. Can be used as a replacement to CMOS based

logic implementation.

TIMELINE 1968 - Argall publishes an article showing the resistance

switching effects of TiO2 which was later claimed in 2008 to be evidence of a memristor by researchers from Hewlett Packard.

1971 - Leon Chua postulated a new two-terminal circuit element characterized by a relationship between charge and flux linkage as a fourth fundamental circuit element.

1976 - Chua and his student Sung Mo Kang generalized the theory of memristors and memristive systems including a property of zero crossing in the Lissajous curve characterizing current vs. voltage behavior.

2008 - On April 15 U.S. Patent was issued to, including basic claims to a nanoscale 2-terminal resistance switch crossbar array formed as a neural network.

2010 – HP teams up with HYNIX to produce a product named re-ram.

2012 -On March 23 HRL Laboratories and the University of Michigan announced the first functioning memristor array built on a CMOS chip for applications in neuromorphic computer architectures

REFERNCES http://www.spectrum.ieee.org/may08/6207 Memristor - Wikipedia, the free encyclopedia Compact models for memristors based on charge flux

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

How We Found the Missing Memristor‖ By R. Stanley Williams, December 2008 · IEEE Spectrum,

http://memristor.pbworks.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

http://www.hpl.hp.com

Thankyou