A New Type of Memristors for Less Rigid Computing Two IT giants, Intel and HP, have entered a race to produce a commercial version of memristors (the fourth basic component of electronic circuits alongside resistors, capacitors and inductors) that could one day replace transistor-based flash memory, used in USB drives, SD cards and SSD hard drives.

�Basically, memristors require less energy since they work at lower voltages,� explains Jennifer Rupp, Professor in the Department of Materials at ETH Zurich and holder of a SNSF professorship grant. �They can be made much smaller than today memory modules, and therefore offer much greater density. This means they can store more megabytes of information per square millimetre.�

Now, a group of researchers funded by the Swiss National Science Foundation have developed a new memristor prototype, based on a slice of perovskite just 5 nanometres thick. The interesting thing about it is that is has not two, but three stable resistive states, meaning it can store both the 0 and 1 of a bit, as well as the 0, 1, and 2 of a �trit�.

The study has been published in the journal ACS Nano.

According to Rupp, the new memristor could be used in future IT that relies on logic, which provides for information located �between� the 0 and 1. This has interesting implications for what is called fuzzy logic, which seeks to incorporate a certain level of uncertainty into the processing of digital information. Rupp calls this �less rigid computing�.

Another possible application could be neuromorphic computing, which, as the name suggests, aims to use electronics in a way that mimics the way neurons process information in organic brains. At any given moment, the properties of a memristor � just like those of a single neuron � depend on what has happened before. In both cases, state shift happens only once a specific activation threshold has been activated.

To explain how the new component works, researchers at ETH Zurich had conducted a series of electro-chemical studies, which they describe in great detail in their new paper.

�We were able to identify the carriers of electrical charge and understand their relationship with the three stable states,� said Rupp. �This is extremely important knowledge for materials science which will be useful in refining the way the storage operates and in improving its efficiency.�

The principles of a memristor were first described in 1971, and since the 2000s, researchers have suggested that certain types of resistive memory could act as memristors.