Battery and memory device in one package
April 25, 2013
Resistive memory cells (ReRAM) are actually not purely passive components but must be regarded as tiny batteries, researchers at Jülich Aachen Research Alliance (JARA) have demonstrated and published in Nature Communications (open access).
Unlike the building blocks of conventional hard disk drives and memories, ReRAM cells are regarded as a promising solution for future generations of computer memories. They promise to dramatically reduce the energy consumption of modern IT systems while significantly increasing their performance.
The new finding radically revises the current theory and opens up possibilities for further applications. The research group has already filed a patent application for their first idea on how to improve data readout with the aid of battery voltage.
Conventional data memory works on the basis of electrons that are moved around and stored. However, even by atomic standards, electrons are extremely small. It is very difficult to control them, for example by means of relatively thick insulator walls, so that information will not be lost over time. This does not only limit storage density, it also costs a great deal of energy.
So researchers are working feverishly all over the world on nanoelectronic components that make use of ions, i.e. charged atoms, for storing data. Ions are some thousands of times heavier that electrons and are therefore much easier to control. In this way, the individual storage elements can almost be reduced to atomic dimensions, which enormously improves the storage density.
Active electrochemical systems
In ReRAMs, ions behave on the nanometer scale in a manner similar to a battery. The cells have two electrodes, made of silver and platinum, for example, at which the ions dissolve and then precipitate again. This changes the electrical resistance, which can be exploited for data storage. But the reduction and oxidation processes also have another effect. They generate electric voltage.
ReRAM cells are therefore not purely passive systems — they are also active electrochemical components. So they can be regarded as tiny batteries whose properties provide the key to the correct modeling and development of future data storage.
In complex experiments, the scientists from Forschungszentrum Jülich and RWTH Aachen University determined the battery voltage of typical representatives of ReRAM cells and compared them with theoretical values. This comparison revealed other properties (such as ionic resistance) that were previously neither known nor accessible.
“The new findings will help to solve a central puzzle of international ReRAM research,” says Prof. Rainer Waser, deputy spokesman of the collaborative research centre SFB 917 ‘Nanoswitches’ established in 2011. In recent years, these puzzling aspects include unexplained long-term drift phenomena or systematic parameter deviations, which had been attributed to fabrication methods.
“In the light of this new knowledge, it is possible to specifically optimize the design of the ReRAM cells, and it may be possible to discover new ways of exploiting the cells’ battery voltage for completely new applications, which were previously beyond the reach of technical possibilities,” adds Waser, whose group has been collaborating for years with companies such as Intel and Samsung Electronics in the field of ReRAM elements.