Memristors

Memory ResistorsAleksey Gladkov

What are They?

Memristor is a portmanteau of the words memory and resistor.

Memristors themselves are passive, two terminal components recently created by HP labs with the ability to “remember” the charge carried across themselves even when there is not current or voltage present.

Memsistor theory was originally proposed by Dr. Leon Chua in a 1971 paper. He is currently employed at UC Berkley.

The Father of Memsistors

More Recently

In 2008, a team at Hewlett Packard Laboratories developed a working model of a memristor using a thin film of titanium dioxide. In October 2011 the same team said that the technology should be commercially available within 18 months.

Some Math

The memristor is a two-terminal variable resistor, with resistance dependent upon the magnetic flux linkage (the integral of the voltage)amount of charge q that has passed between the terminals.

A Bit of Substitution

Some substitution gives us the memristance as a function of charge over time, and, more importantly, as a function of voltage and current.

Structure

The device developed by HP Labs consists of a 50nm thin film of titanium dioxide with 5nm electrodes on either side. There are two layers to the film, one of which is oxygen depleted.

Function

The oxygen depleted spots act as charge carriers, and drift when an electric filed is applied, changing the combined resistance of the two layers. The carriers can be moved back by introducing a reversed flow of charge, which causes the device to return to it's initial state. The memristor will maintain its configuration even if the current is cut off, making it a more robust memory solution compared to the devices currently on the market.

What it all Means

As shown in the image to the left, memristors fill a previous gap in our knowledge of electronics, by providing a passive component which relates flux to charge.

Some Applications

In April of 2010 HP Labs announced that they had created a memristor with a switching speed of about 1ns (~1GHz) and a footprint of 3x3 nm. Since then, they have created some sample devices, capable of containing 12 GB of data per square cm, and are looking to increase that to 20 GB by 2013.

True Potential

The true potential of memristors lies in the fact that they are capable of having dozens, if not hundreds of different states, instead of just the two that we have come to associate with computing.

Memristors are also capable of performing logic functions, which means that the current compartmentalized structure of computing could very well be on its way out, as we create devices capable of both storing and processing data in the same space.

Questions?

References

MIT Technology Review <http://www.technologyreview.com/computing/25018/page2/>.

Wikipedia: Memristor <http://en.wikipedia.org/wiki/Memristor>.

Computer World <http://www.computerworld.com/s/article/9216745/HP_advances_next_gen_memristor_memory_technology?taxonomyId=19&pageNumber=1>

HP Labs<http://www.hpl.hp.com/news/2010/apr-jun/memristor.html>

All Images courtesy of google images