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Surprising Property of Ferroelectrics Might Lead to Smaller, Lighter Electronics

Surprising Property of Ferroelectrics Might Lead to Smaller, Lighter Electronics
In this artist’s conception, a needle from a scanning impedance microscope touches a domain wall in a ferroelectric material. Image credit: Ella Maru Studio.

A research team led by physics professor Keji Lai at the University of Texas at Austin has discovered that a material he studies has an unusual property that could one day lead to cell phones and other electronic devices that are smaller, lighter and more energy efficient.

To understand the unique property, first imagine you put a frozen burrito on a plate in a microwave oven and then turn it on. Notice how the burrito gets hot, but not the plate. The researchers discovered that something similar happens when they zap a certain material, called a ferroelectric, with microwave radiation.

Microwave radiation moves like a wave on the ocean, with peaks and troughs. When it hits your burrito, the water molecules flip end over end and generate heat. But not the plate; it doesn't contain water. Lai and his team discovered that when microwave radiation hits ferroelectrics, it causes narrow bands of atoms called domain walls to flip end over end too, but not the other atoms. In both cases—burritos and ferroelectrics—the flips are synchronized with the vibrations of the microwaves.

This research shows that domain walls can serve two functions—transmit microwave radiation and filter out other frequencies of radiation. Lai says these properties could allow engineers to replace two components in a cell phone with one, thus reducing its overall size, weight and energy use. The material could also be used in electronic instruments designed to be sent into space, where size and energy use are critical factors.

In this scanning impedance microscope image of a ferroelectric material, the light-colored wavy lines are domain walls. The yellow scale bar is 1 micron long, about the width of the smallest bacteria.

The research is published in the May 10 edition of the journal Science Advances.

The discovery took several years of painstaking work and was made possible by a device called a scanning impedance microscope, which uses a needle with an exceedingly fine point, just 10 to 100 nanometers wide. That allowed them to direct microwaves to very specific spots on the surface of a ferroelectric material and show that only the domain walls reacted by shaking in time with the radiation.

Lai suggests that this property could also make ferroelectric materials useful in a radically new kind of electronic chip in which circuits can be rewired with the flip of a switch. In simple terms, imagine a path made up of domain walls that carry a microwave signal though an electronic component from the south to the north. You could potentially turn some of the domain walls such that the path of the microwaves would now take a right hand turn from the south to the west.

"In integrated circuits, a signal is guided along fixed lines," says Lai. "Once it's built, it's built. That's not the case with reconfigurable components."

Lai cautions that the discovery of this unusual property in a ferroelectric is just the first of many steps that would be needed to realize a practical reconfigurable component.

Lai's co-authors are: Xiaoyu Wu, Lu Zheng and Yuan Ren at UT Austin; Urko Petralanda and Sergey Artyukhin at Istituto Italiano di Tecnologia; and Rongwei Hu and Sang-Wook Cheong at Rutgers University.

Funding for this research was provided by the National Science Foundation, the U.S. Army Research Laboratory, the U.S. Army Research Office and the Gordon and Betty Moore Foundation.

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Thursday, 25 May 2017

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