Meso Nano and Microscale Technologies

There are important electronic properties in electronic technologies that change when responding to voltage or current.  Scientists want to understand these changes, in terms of a substance's structure at the microscale, nanoscale and mesoscale. 

The microscale is the thickness of a piece of paper and the nanoscale is a few atoms thick. Beyond that, there is a realm that is seldomly mentioned. It spans from 10 billionths to 1 millionth of a meter, named the mesoscale.  

Researchers at the US Department of Energy (DOE) Argonne National Laboratory are working with Rice University and DOE's Lawrence Berkley National Laboratory. The teams are working together to widen their understanding of the mesoscale properties of a ferroelectric substance under an electric field. The research was published in August's edition of the journal Science. 

The research examines potential improvements in computer memory, sensors for ultra precise measurements and even lasers used in scientific instruments. 

The material examined is ferroelectric. It's a complex mixture of magnesium, niobium, lead, titanium and is an oxide. Researchers are calling this material a relaxor ferroelectric. It is distinguished by pairs of positive and negative charges, or dipoles, that group into into clusters called "polar nanodomains".

The dipoles align in the same direction when under an electric field. This causes the substance to strain and shape. Correspondingly, applying a strain can change the dipole direction, which creates an electric field. 

Yue Cao is an Argonne physicist. He states, "If you analyze a material at the nanoscale, you only learn about the average atomic structure within an ultra small region. But materials are not necessarily uniform and do not respond in the same way to an electric field in all parts. This is where the nanoscale can paint a more complete picture bridging the nano to microscale."

Professor Lane Martin's group at Rice University created a fully workable deice that is based on relaxor ferroelectric. It was designed to test the substance under similar operating conditions.  The main component of the relaxor ferroelectronic device is a very thin film that measures 55 nanometers. It is placed in between nanoscale layers. These serve as electrodes that researchers can apply voltage to produce an electric field.

Using photon measuring tools, the Argonne team was able to map the mesoscale structures inside the relaxor. Researchers used coherent X-ray nano diffraction. It is available through the Hard X-ray nanoprobe which is run by the Center for Nanoscale Materials at Argonne and the APS.

The results are interesting. They show that under an electric field the nanodomains self assemble into mesoscale constructs, made of dipoles that align in a very complex tile-like pattern. This occurs along the borders of the pattern and any region that appears to respond more strongly to the electric field. 

John Mitchell is an Argonne Distinguished Fellow. He states "These submicroscale structures represent a new form of nanodomain self assembly not known previously. Amazingly, we could trace their origin all the way back to underlying nanoscale atomic motions."

Lane Martine is quoted as saying, "Our insights into the mesoscale structures provide a new approach to the design of smaller electromechanical devices that work in ways not thought possible."

Hao Zheng is the lead author of this research and is a beam line scientist at the APS. He says, " The brighter and more coherent X-ray beams now possible with the recent APS upgrade will allow us to continue to improve our device. We can assess whether the device has application for energy efficient micro electronics, such as neuromorphic computing modeled on the human brain."

Microelectronics that are low powered are important for keeping up with the demands of cell phones, desk top computers and super computers around the world!