UNO-AMRI Spearheads Discoveries Expected to Substantially Increase Data Storage Capacity

Research that started several years ago at the University of New Orleans has led to groundbreaking discoveries expected to substantially increase data storage capacity -- allowing cell phones, computer hard drives, memory flash drives and other technological devices to increase their storage capabilities six-fold, while becoming cheaper, lighter and more-energy efficient.
 
The scientific achievements of Gabriel Caruntu and his colleagues, revealed this month in Nature Materials, one of the world’s most prestigious scientific journals, are considered to form a cornerstone of nanoscience and nanotechnology, or the study and application of extremely small things.
 
“It’s hard for me to put it in simple words,” said Caruntu, who joined UNO’s Advanced Materials Research Institute (UNO-AMRI) in 2008. “We’re just at the beginning.”

Scientific breakthroughs

Caruntu, an assistant professor of chemistry and materials science at UNO, conducts much of his research in the field of nanotechnology, which is science, engineering, and technology conducted at the nanoscale, or the study and application of extremely small things.
 
To put his work in perspective, Caruntu gave this analogy: A human is one billion times smaller than the sun, and one nanometer is one billion times smaller than a human.
 
Caruntu and UNO graduate assistant Amin Yourdkhani belong to an interdisciplinary team of scientists whose members hail from the U.S. Department of Energy and research institutions including the University of California-Berkeley, Brookhaven National Laboratory, Lawrence Berkeley National Laboratories and Central Michigan University. Together, the scientists recently achieved several “firsts” in their field.
 
Using the world’s most powerful microscopes, the scientists were able to visualize individual atoms, getting a close look at not only the atoms themselves, but at electrical dipoles located on the atoms they form, said I.R. “Poncho” De Leon, assistant director of UNO-AMRI.
 
Dipoles are transmitters of sorts: two equal and opposite magnetized or electrically charged poles separated by a short distance. By using sophisticated electron microscopy techniques, the scientists were able to visualize for the first time the position of atoms composing a free-standing nanometer-sized ferroelectric particle.

They achieved the world's closest look at the atom.
 
A close look at atomic particles and how they work
 
Very few microscopes in the world are able to view atoms at the molecular level – two of them are located at the laboratories at Brookhaven and UC-Berkeley, Caruntu said. The electron microscopes’ resolution goes below the nanometer scale down to the angstrom scale, or atomic resolution.
 
Working off cutting-edge research that Caruntu began in 2009, the interdisciplinary team used these electron microscopes to analyze the positions of ions, or electrically charged atoms, in polar materials and to investigate elements of ferro-electricity at the nanoscale.
 
(Ferro-electricity is a phenomenon described as the existence of a spontaneous, switchable polarization as a result of crystal asymmetry in some materials. The effect is similar to that of an electrical current.)
 
While arriving at their conclusions, researchers became the first in history to get an up-close look at the polar structure – electrical dipoles of an individual ferroelectric nanocrystal, never seen before today at quite the same degree of proximity, Caruntu said.
 
“These experiments helped the researchers to gain a fundamental understanding about the distribution of the electrical dipoles within the crystal structure -- and its dependence on temperature or electric fields, which are ultimately responsible for the amazing properties of these materials,” De Leon said.
 
“Scaling down the size of these materials while preserving their properties, and assembling them into devices will open the door to the design of cheap, portable and low power consumption electronic devices with ultra-high storage capacity.”
 
Early work at UNO-AMRI
 
In recent years at UNO-AMRI, Caruntu has studied perovskites, a class of naturally occurring ferroelectric minerals which have been used in the design of electronic components.  Perovskites have the unique property of having a structural asymmetry, which leads to the formation of electrical dipoles, De Leon said. The generation and manipulation of such dipoles make perovskites key materials for use in many advanced technologies such as data sensing, data storage and energy conversion.
 
Since 2009, Caruntu has examined the behavior of these materials at the microscale and the nanoscale, with the immediate goal of understanding the materials’ internal structure and mechanism of formation, along with their size and shape.
 
In this work, Caruntu held an eventual goal of fabricating perovskites with predictable properties which can be integrated into various types of functional devices.
 
“We are among the very few labs in the world that are able to fabricate these materials with a very high quality,” said Caruntu. “I was interested in getting more information about what happens with the ferroelectric properties of these materials when the size of the constituting grains is decreased to the nanometer-sized scale -- and initiated the collaboration with other labs, both in the U.S. and Europe. We were first interested in performing these kinds of fundamental experiments to investigate the existence of electrical dipoles, visualize them and understand the conditions responsible for their stability and/or suppression. This is what scientists do.”
 
Worldwide Interest
 
Worldwide interest in his latest scientific research stems from intense need to increase data storage capacity, said Caruntu, who said that flash memory drives and other daily devices include natural materials applied to science. (Although public awareness related to the use of these materials is low, they have permeated all aspects of modern technologies.)

Five years ago, people were happy to be able to have conversations over the cellular phone and send text messages, he said. Now, they want to transfer video files, even fast-transfer them.
 
Ever-increasing use of data storage devices has naturally also led to an interest in devices with increased capacity and lower power consumption developed in a smaller size at lower cost.
 
In recent years, computational chemists have predicted that, similar to their magnetic counterparts, the dipoles in nanoscale ferroelectrics can organize into circular patterns instead of the rectilinear, or straight-line, patterns described in existing theories.
 
“It’s been a big race for experimentalists to try to prove this,” said Caruntu. “The way we control and manipulate these small dipoles is the key to improving the performance of these materials,” he said.
 
“At the same time, we are trying to scale down the device, to decrease the size of the grains these materials are made of. The smaller the grains are, the more information we can store. However, there is a physical limit below which the electrical dipoles disappear. This fundamental problem is known as the limit of ferroelectric order -- the size at which the spontaneous polarization will be eradicated and this causes the loss of the data stored in devices incorporating such materials.”
 
Memory expansion
 
In an attempt to address these questions, Caruntu’s team uncovered the existence of dipoles for aggregate-free nanocrystals -- and confirmed that nanocrystals as small as 10 nanometers are able to retain electricity.
 
This means that ultimately manufacturers would be able to make materials wherein each individual nanocrystal could store one bit of information, Caruntu said.
 
“This work points the way to multi-terrabytes per square inch memory. Now the storage capacity on a commercial flash memory is 120 gigabytes, so we can increase this to multiple terrabytes per square inch.”
 
The team’s discoveries are expected to lead to more cutting-edge discoveries as experimentalists race to continue to improve technology.
 
Future applications
 
The groundbreaking discoveries could have many applications, including applications in the biomedical field, said Caruntu. Understanding how electrical dipoles work in nanocrystals could also be pivotal to advancements in understanding primary sources of energy and energy use.
 
“Solar energy is abundant and, more importantly, free. And most of solar energy is wasted because we cannot convert it efficiently into chemical or mechanical,” Caruntu said. “We are interested in using these examples in directing these materials as catalysts to split water -- for example, if we split water into hydrogen and oxygen, hydrogen can be used as an environmentally-friendly fuel in vehicles. And these materials seem to be promising in this field.”
 
The discoveries, published this month in Nature Materials under the title “Ferroelectric order in individual nanometer scale crystals” are reverberating in scientific periodicals around the world, and opening doors for UNO-AMRI, where scientists plan to continue advancing their research through integrating these materials into devices, such as capacitors and tiny transistors, and testing them, said Caruntu.
 
“This is the beginning of the journey, I hope, because these results are very exciting,” Caruntu said.  “We’ll be trying to do more work on this, to get more information on the internal structure and properties of these crystals and to integrate them into functional devices such as nanocapacitors and transistors. In the long term, these structures show a great potential towards commercialization but, for now, we can’t do commercialization from the lab bench. So this has to be integrated into the device, and the device should be tested, optimized."