This document discusses memristors, a fourth fundamental circuit element predicted in 1971 and realized in 2008. Memristors are two-terminal devices whose resistance depends on the history of applied voltages. The first memristor was created at HP Labs using a thin film of titanium dioxide sandwiched between platinum electrodes. By drifting oxygen ions with an electric field, the device's resistance could be switched to represent binary data states. Memristors could replace other non-volatile memory types and even mimic neural behaviors, with potential applications in memory, programmable logic, and neuromorphic computing.

1. MEMRISTORS
PRESENTED BY UNDER THE GUIDANCE OF
ABHISHEK KUMAR DR. D. K. SRIVASTAVA
1104331002

2. 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

3. 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”

4. 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

5. THE FOURTH ELEMENT

6. 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

7. 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.

8. FEATURES OF A MEMRISTOR
The characteristic of a Memristor is its MEMRISTANCE
(M)
Φ = M q
It 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.

9. PIPE AND CURRENT ANALOGY

10. MATHEMATICAL ANALYSIS
Φ = M q

11. CURRENT-VOLTAGE BEHAVIOUR IN RESISTORS AND MEMRISTORS

12. 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.

13. 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.

14. TiO2-x
TiO2

15. 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.

16. 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.

17. 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.

18. 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

19. 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

20. Thank
you