Nav: Home

Tiny supersonic jet injector accelerates nanoscale additive manufacturing

July 02, 2019

By energizing precursor molecules using a tiny, high-energy supersonic jet of inert gas, researchers have dramatically accelerated the fabrication of nanometer scale structures. The rapid additive manufacturing technique also allows them to produce structures with high aspect ratios. Now, a theory developed to describe the technique could lead to new applications for additive nanomanufacturing and new nanoscale materials.

Based on focused electron beam deposition, the technique allows structures to be fabricated from gas-phase precursors at rates approaching what could be expected in the liquid phase - all without raising the temperature of substrates. That could lead to manufacturing of the nanometer-scale structures at rates that could make them practical for use in magnetic memory, high-frequency antennas, quantum communication devices, spintronics and atomic-scale resonators.

"We are controlling matter on the atomic scale to bring about new modes of additive manufacturing," said Andrei Fedorov, a professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. "This new science could bring about additive manufacturing applications that might otherwise be impossible. The resulting new technology will open up new dimensions for additive manufacturing at the atomic scale."

The work grew out of frustration with trying to create small structures using the electron beams, which can be just a few nanometers in diameter. The research was supported by the U.S. Department of Energy's Office of Science, and was reported May 28 in the journal Physical Chemistry Chemical Physics.

"When we went to the lab to use nanofabrication with focused electron beams, which are the size of a few nanometers, we could not grow structures that were just a few nanometers. They grew to be 50 or 100 nanometers," Fedorov explained. "And it also took a long time to produce the structures, which meant that, without improvements, we'd never be able to produce them at high volume."

Fedorov and collaborators Matthew Henry and Songkil Kim realized the reactions producing the structures were slow, and tied to the thermodynamic state of the substrate on which they are being grown. They decided to add some energy to the process to speed things up - as much as a hundred times faster.

The result was the invention of a micro-capillary injector just a few micrometers in diameter that could introduce tiny jets of gaseous molecules into the deposition chamber to activate the precursors for the nanometer-scale structures. Partly because the jet is entering a vacuum chamber, the gas accelerates to supersonic speeds. Energy from the supersonic jet excites the precursor molecules that are adsorbed to the substrate.

"This energetic thermal state allows the electrons from the beam to much more easily break chemical bonds, and as a result, structures grow much faster," Fedorov said. "All of this amplification, both the molecule transport and the rate of reaction, are exponential, meaning a small change can lead to a dramatic increase in outcome."

That much has been observed experimentally, but to understand how to control the process and expand its applications, the researchers wanted to create a theory for what they were seeing. They used nano-scale thermometric techniques to measure the temperature of the adsorbed atoms - also known as adatoms - subjected to the jet, and used that information to help understand the basic physics at work.

"Once we have a model, it essentially becomes a design tool," Fedorov said. "With this understanding and the capabilities we have demonstrated, we can expand them to other fields such as directed self-assembly, epitaxial growth and other areas. This could enable a whole host of new capabilities to use this kind of direct-write nanofabrication."

Development of the model and understanding of the first-principles physics behind it could also allow other researchers to find new applications.

"With this, you can have almost the same order of magnitude growth rate as you'd have with liquid phase precursors, but still have access to the richness of possible precursors, the ability to manipulate alloying, and all the experience that has been developed over the years with gas phase deposition," Fedorov said. "This technology will allow us to do things at a scale that is meaningful from a practical standpoint and cost-effective."

The ability to rapidly produce small, three-dimensional structures could open up a range of new applications.

"If you can adapt additive direct-write techniques, this could bring a lot of unique capabilities for magnetic memory, superconducting materials, quantum devices, 3D electronic circuitry, and many more things," he said. "These structures are currently very hard to make using conventional methods."

Beyond using the jets to accelerate deposition of precursor materials already on the substrate, the researchers have also created hybrid jets that contain both high-energy inert gas and precursor gases, which allow not only dramatic acceleration of nanostructure growth but also precisely control the material composition during growth. In future work, the researchers plan to use these hybrid approaches to enable formation of nanostructures with phase and topology that cannot be achieved by any existing nanofabrication techniques.
-end-
This research was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award #DE-SC0010729.

CITATION: Matthew R. Henry, Songkil Kim and Andrei G. Fedorov, "Non-equilibrium adatom thermal state enables rapid additive nanomanufacturing." (Physical Chemistry Chemical Physics, 2019) http://dx.doi.org/10.1039/c9cp01478k

Georgia Institute of Technology

Related Lead Articles:

Stroke patients take the lead in their rehabilitation
EPFL spin-off Intento has developed a patient-controlled electrical-stimulation device that helps stroke victims regain mobility in paralyzed arms.
Preventing lead spread
While lead pipes were banned decades ago, they still supply millions of American households with water each day.
Evidence lacking to support 'lead diet'
Writing in the Journal of Pediatrics, UB researcher says public health experts need to be more up front with parents in explaining that CDC dietary recommendations may not help children who have been exposed to lead.
New drug lead identified in fight against TB
Antibacterial compounds found in soil could spell the beginnings of a new, much-needed treatment for tuberculosis, new research led by the University of Sydney has found. tuberculosis (TB) causes more deaths than any other infectious disease including HIV/AIDs.
Lead dressed like gold
Princeton researchers have taken a different approach to alchemists' ancient goal to transmute elements by making one material behave that another.
Iron supplements in the fight against lead
Targeted iron supplements in biscuits can achieve a striking reduction in the level of lead in children's blood in regions with high exposure to this toxic heavy metal.
A more accurate sensor for lead paint
A new molecular gel recipe developed at the University of Michigan is at the core of a prototype for a more accurate lead paint test.
Using urban pigeons to monitor lead pollution
Tom Lehrer sang about poisoning them, but those pigeons in the park might be a good way to detect lead and other toxic compounds in cities.
Looking beyond conventional networks can lead to better predictions
New research from a team of University of Notre Dame researchers led by Nitesh Chawla, Frank M.
What can we expect next in the long history of lead poisoning in the US?
While state and federal officials continue to criticize each other for failing to guarantee safe drinking water, the question of exactly who is responsible for crises like in Flint, Michigan, lies at the root of the problem.

Related Lead Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...