The memristor was first postulated in a paper published in 1971 by Professor Leon Chua, from the University of California Berkeley. He looked at the basics of circuit design and saw four variables, but only three elements – resistor, capacitor and inductor. His view was the fourth fundamental circuit element – the memristor – would combine resistance and memory, properties that cannot be duplicated by any combination of the other three elements. However, the memristor remained theoretical until its discovery in 2008 by a team led by Dr Stan Williams of HP Labs, pictured.
The memristor is thought to enable more energy efficient computing systems, with memories that retain information even after the power is off. The researchers also believe it may be possible to create systems with some of the pattern matching abilities of the brain.
When HP announced its discovery of the memristor, it said the crucial issue was for the device's atoms to change location when a voltage was applied. In the latest work, the HP/UC Santa Barbara team looked to map the chemistry and structure of the conductive channel responsible for the switching in the device.
By using highly focused xrays, the team probed the memristor, discovering a 100nm region with concentrated oxygen vacancies where the memristive switching occurs. This region was surrounded by a newly developed structural phase, which acted like a thermometer telling researchers where and how hot it became.
In a paper published in Nanotechnology, the team noted: "We resolved a single conducting channel that is made up of a reduced phase of … titanium oxide. Moreover, we observed sufficient Joule heating to induce a crystallisation of the oxide surrounding the channel, with a peculiar pattern that finite element simulations correlated with the existence of a hot spot close to the bottom electrode, thus identifying the switching location."
For more on memristors, click here and here.
