Dutch research teams breakthrough in non-volatile plastic memory could pave the way for innovative new radio frequency tag applications.
Researchers at the University of Groningen in Holland and scientists at Philips Research have made a major breakthrough in plastic electronics. They have for the first time developed a non-volatile plastic memory technology that meets the performance needs of commercial plastic electronics applications such as radio frequency (RF) identification tags.
The researchers claim that the new technology could do for plastic electronics what Flash memory has done for silicon chips.
The advent of Flash - a non-volatile memory that does not lose its data when the power is turned off - revolutionised consumer electronics. It is used to store the numbers in mobile phones, the pictures taken with digital cameras and the music tracks in MP3 players.
Non-volatile memory could also play a major role in plastic electronics, paving the way for innovative applications such as food packaging that can alert consumers when its contents are close to their use-by date and power-saving electronic price tags that remember the sale price even when they are turned off.
The non-volatile plastic memory developed by the University of Groningen and Philips Research teams is based on organic field-effect transistors in which the gate dielectric (the insulating layer between the transistors gate and its channel) is composed of a polymer ferroelectric material. Ferroelectrics are materials that can be switched between two different charge states using 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 transistors drain electrode and detecting whether or not current flows in its channel. Although ferroelectric field effect transistors have been researched before, the University of Groningen/Philips Research team is the first to produce a device with short programming time, long data retention time and high programme-cycle endurance using a low-temperature low-cost technology. In addition, all the devices 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.” An important feature of the fabrication process is the ability to deposit the ferroelectric layer as well as the other layers out of a solution. This makes the process suitable for large-scale industrialisation using low-cost techniques such as spin-coating or printing.
The low process temperature also allows the manufacture of memory on flexible substrates such as cheap plastics.