Plastic memory

Researchers at the University of Groningen in the Netherlands and scientists at Philips Research have developed novel organic field-effect transistors that use a polymer ferroelectric gate dielectric.


Researchers at the University of Groningen in the Netherlands and scientists at Philips Research have developed novel organic field-effect transistors that use a gate dielectric (the insulating layer between the transistor’s gate and its channel) composed of a polymer ferroelectric material.



Ferroelectrics are materials that can be switched between two different ‘charge’ states by the application of a high voltage pulse. Each state is stable, persisting long after the voltage pulse is removed.



Although FeFET (Ferroelectric Field Effect Transistor) structures have been developed before, the University of Groningen/Philips Research team claims that it’s the first to produce a device with a short programming time, long data retention time and high program-cycle endurance using a low-temperature low-cost technology.



‘One of the major breakthroughs we have made is finding ways of laying down the different layers of material in such a way that the ferroelectric effect is not masked by other effects such as charge trapping at the interface between the ferroelectric and semiconducting layers or by material impurities,’ said Ronald Naber at the University of Groningen.



All the device’s operating voltages, such as the voltage needed to program and read individual memory cells, are within the limits of RFID tagging applications, and can be reduced even further by downscaling of the transistor dimensions.



An important feature of the fabrication process is that the ferroelectric layer, as well as the other layers, can deposited from a solution, which means that spin-coating or printing techniques can be used to make the devices. The low process temperatures also suit the fabrication of memories on flexible substrates such as cheap plastics.