Low-power, high-efficiency electronic memory comes closer to reality

April 17th, 2009 - 1:28 pm ICT by ANI  

Washington, Apr 17 (ANI): Paving the way for low-power, high-efficiency electronic memory, scientists have deposited a well-known oxide on silicon to create a ferroelectric state, which could be the key to next-generation memory devices.

For the study, Cornell materials scientist Darrell Schlom took strontium titanate, and deposited it on silicon in such a way that the silicon squeezes it into a special state called ferroelectric.

One can see ferroelectric materials in “smart cards” that are used in many subways and ski resorts, and are made with materials like lead zirconium titanate or strontium bismuth tantalate, which can instantly switch between different memory states using very little electric power.

When waved before a reader, a tiny microwave antenna inside the card reveals and updates stored information.

The study is the first to use ferroelectric materials in transistors, which could lead to “instant-on” computing - no more rebooting the operating system or accessing memory slowly from the hard drive.

“Adding new functionality to transistors can lead to improved computing and devices that are lower power, higher speed and more convenient to use. Several hybrid transistors have been proposed specifically with ferroelectrics in mind. By creating a ferroelectric directly on silicon, we are bringing this possibility closer to realization,” said Schlom.

While strontium titanate in its relaxed state is not ferroelectric at any temperature, the researchers have shown that extremely thin films of the oxide - just a few atoms thick - become ferroelectric when squeezed atom by atom to match the spacing between the atoms of underlying silicon.

“Changing the spacing between atoms by about 1.7 percent drastically alters the properties of strontium titanate and turns it into a material with useful memory properties,” said Long-Qing Chen, professor of Materials Science and Engineering at Pennsylvania State University.

It was Chen’s calculations that had predicted the observed behaviour five years ago.

The researchers successfully described how to grow the strontium titanate on top of silicon using molecular-beam epitaxy-a technique akin to atomic spray painting.

The study has been published in the journal Science. (ANI)

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