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Hybrid organic/inorganic memory elements for integration of electronic and photonic circuitry

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New mechanisms of memory storage

Non-volatile memory (NVM), in contrast to random access memory, retains information even with no power input. NVM elements that can be addressed optically as well as electrically extend functionality and open new markets.

Digital Economy

Despite its huge savings in energy consumption and the potential for much faster data transfer, NVM is currently used as secondary or long-term storage. Enhancements in materials and device capabilities are an important area of research and development. EU-funding of the HYMEC (Hybrid organic/inorganic memory elements for integration of electronic and photonic circuitry) project supported investigations into the fundamental information storage mechanisms of nano-structured hybrid materials. New knowledge led to the realisation of NVM elements based on resistance switching and an extension of functionality to enable optical and electrical addressing of devices. Resistance switching refers to a change in resistance of a dielectric when exposed to an electric field or current. Typical systems employ a transition metal oxide dielectric and an ordinary metal electrode. The change in resistance is non-volatile and reversible. HYMEC identified the resistance switching mechanisms of a system consisting of inorganic metal nanoparticles embedded in matrices of conjugated organic materials (organic semiconductors). It is based on filament formation rather than charge storage on the metal nanoparticles, as has been assumed to date. This discovery meant that direct manipulation of the resistance by light was not possible. The team turned its attention to the device's diode in series with the memory that was used to implement the single memory elements into a device network. By using the diode instead of the memory resistor for the optical addressing, HYMEC successfully extended the functionality of the NVM element without compromising overall system performance. The team used a combination of state-of-the-art experimental and theoretical techniques to extensively characterise system properties. Enhanced understanding supported establishment of reliable design rules for such devices in technologically relevant applications and was instrumental in establishing cost-efficient production routes. Researchers also explored miniaturisation of NVM elements by novel nano-structuring processes. HYMEC NVM technology that is both electrically and optically accessible is expected to have major impact on a new generation of devices integrating photonics and electronics. Low-cost production and miniaturisation will further enhance the attractiveness of the functionality for a leading European role in a growing market sector.

Keywords

Memory storage, non-volatile memory, data transfer, memory elements, electronic and photonic

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