Plastic fantastic
The researchers claim that the new plastic memory could pave the way for totally new concepts such as food packaging that can alert consumers when its contents are getting close to their use-by date and power-saving electronic price tags that remember the sale price even when they are turned off.
The new plastic memory technology was made using organic field-effect transistors in which the gate dielectric (the insulating layer between the transistor's gate and its channel) is 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.
Because each state is stable, persisting long after the voltage pulse is removed, the transistor can be used as a memory device. The charge difference between these two states changes the threshold voltage (turn-on voltage) of the transistor, which means that the contents of the memory can be read electrically by applying a voltage to the transistor's drain electrode and detecting whether or not current flows in its channel.
Although ferroelectric field effect transistor (FeFET) structures have been researched before, the University of Groningen/Philips Research team is the first to produce a device with a short programming time, long data retention time and high programme-cycle endurance using a low-temperature lowcost technology.
In addition, all the device's operating voltages, such as the voltage needed to programme and read individual memory cells, are within the limits of tagging applications, and can be reduced even further by downscaling the transistor dimensions.
"Knowing the physics and making it work are two different things," said Ronald Naber of the University of Groningen.
"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."