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Using light to store information with photo-ferroelectric materials

ICMAB researchers have discovered that, through the application of pulsed light, photoresponsive ferroelectric materials can switch from a low-resistance to a high-resistance state. These materials have made possible the design of memories that are able to store information permanently in different resistance states.

The studied devices combine light sensor and memory functions. These devices behave like a memristor, a device that can display multiple resistance states according to the stimulus it has received. Memristors are one of the basic devices needed for the development of neuromorphic computing systems, a technology in development that imitates the functioning of neuron biological systems. Therefore, the developed device opens a path to be explored in relation to its integration into neuromorphic vision systems, where the system learns to recognize images.

While commercial electric memories are based in the writing of information by pulsed electric light, the developed device with photo-ferroelectric materials will allow storing information permanently by optical means and without using a pulsed light.

Applications

These new devices could be applied in the future to make “sensors with memory” for cameras or data storage, for example.

Today, applications of neuromorphic vision are already available in systems of assisted driving and robots. However, these devices are made of a complex wire structure with sensors, processors and memories, so a simpler system is desirable. This is precisely what the developed device will bring along: a sole element that integrates all these other devices and achieves to replicate the functional properties of the human eye.

Ignasi Fina, ICMAB researcher and co-author of the study, explains that “materials that show changes of resistance under illumination are abundant, although the effect is typically volatile and the material recovers its initial state after some dwell time. For devices that are going to be used in computing and data storage in the future, non-volatile optical control of electrical resistance is of potential interest. ‘Non-volatile’ means that the information can be retained in the device, even when the power is off”.

In the explored photo-ferroelectric devices, an electric field is used to write and change the ON/OFF states, combined with the optical stimulus, and modulate the resistance from high to low.

These devices are energetically efficient for two main reasons: firstly, the energy consumption is reduced when the memory state is written, as it does not need any charge current flow. Secondly, as the information is stored in a non-volatile manner, the state is preserved and there is no need to refresh the information (re-writing) as is continuously done in current computer DRAM memories, for example.

The observed optical switch is not restricted to the studied materials and, thus, opens a path towards further investigations on this phenomenon.

The study has been published in Nature Communications. One of the authors, Ignasi Fina, has been granted with a BBVA Foundation Leonardo Grant to further explore this topic.

Reference

Non-volatile optical switch of resistance in photoferroelectric tunnel junctions
Xiao Long, Huan Tan, Florencio Sánchez, Ignasi Fina, Josep Fontcuberta
Nature Communications, 2021
DOI: 10.1038/s41467-020-20660-9

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