By exciting precursor molecules with a tiny, high-energy supersonic inert gas jet, researchers have dramatically accelerated the production of nanometer-scale structures. The fast additive manufacturing technology also allows them to produce structures with high aspect ratios. A theory developed to describe the technique could now lead to new applications for additive nanoproduction and new nanoscale materials.
Based on focused electron beam deposition, this technique can produce structures of gas phase precursors at rates approaching those expected in the liquid phase without increasing the temperature of the substrates. This could lead to structures in the nanometer range being produced at rates that are practical for use in magnetic memories, radio frequency antennas, quantum communication devices, spintronic and atomic resonators.
"We control matter at the atomic scale to create new modes of additive manufacturing," said Andrei Fedorov, a professor at the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. "This new science could lead to additive manufacturing applications that would otherwise be impossible, and the resulting new technology will open new dimensions for additive manufacturing at the atomic level."
the electron beams, which can be only a few nanometers in diameter. The research was supported by the US Department of Energy and published on May 28 in the journal Physical Chemistry Chemical Physics .
"When we went to the lab to use nanofabrication with focused electron beams With a size of a few nanometers, we could not build structures that were only a few nanometers in size and grew to 50 or 100 nanometers," Fedorov said. "And it took a long time to fabricate the structures, which meant we would never be able to produce them in large numbers without improvements."
Fedorov and co-workers Matthew Henry and Songkil Kim realized the reactions that the structures were slow and bound to the thermodynamic state of the substrate on which they grow. They decided to put some energy into the process to speed it up – up to a hundred times faster.
The result was the invention of a microcapillary injector measuring only a few microns in diameter, capable of injecting tiny gaseous molecules into the deposition chamber to activate precursors to nanometer-sized structures. Partly because the jet enters a vacuum chamber, the gas accelerates to supersonic speed. The energy of the supersonic jet excites the precursor molecules adsorbed on the substrate.
"This energetic heat state allows the electrons of the beam to break up chemical bonds much more easily, and as a result, the structures grow much faster," said Fedorov. "All of these amplifications, both the molecular transport and the reaction rate, are exponential, which means that a small change can result in a dramatic increase in the result."
This was experimentally observed, but to understand how to control it. The researchers processed and expanded their applications and wanted to create a theory for what they saw. They used nanoscale thermometric techniques to measure the temperature of the adsorbed atoms – also called adatoms – exposed to the beam, and used this information to understand basic physics at work.
"Once we have a model, we have it essentially becomes a design tool," said Fedorov. "With this understanding and the skills we have demonstrated, we can extend them to other areas, such as directional self-organization, epitaxial growth, and other areas, which could allow a whole new set of capabilities, such as direct nanofabrication to use." "
Developing the model and understanding the underlying physics of the first principles may also allow other researchers to search for new applications."
"This gives you almost the same growth rate as you have with liquid phase precursors, but We still have access to the wealth of possible precursors, the ability to manipulate alloying, and all the experience gathered over the years of gas phase separation, "said Fedorov." This technology will allow us to scale things up
The ability to quickly create small three-dimensional structures could open up a whole new set of applications.  "If you can adapt to additive direct-writing techniques, this could have a lot of unique abilities for Magnetic memory, superconducting materials, quantum g devices, 3D electronic circuits, and more, "he said. "These structures are currently very difficult to produce using conventional methods." In addition to using the nozzles to accelerate the deposition of precursor materials onto the substrate, researchers have also developed hybrid nozzles that contain both high energy inert gas and precursor gases that not only dramatically accelerate nanostructure growth, but also increase material composition during growth Control growth precisely. In future work, researchers plan to use these hybrid approaches to form nanostructures with phases and topologies that can not be achieved with any of the existing nanofabrication techniques.
3D nano bridges formed by electron beam writing with tiny jets of liquid precursor
Matthew R. Henry et al., Non-equilibrium Adatom Heat State Enables Rapid Additive Nanoproduction, Physical Chemistry Chemical Physics (2019). DOI: 10.1039 / c9cp01478k
Small supersonic jet injector accelerates nanoscale additive manufacturing (2019, July 2)
retrieved on 3 July 2019
This document is subject to copyright. Apart from any fair dealings for the purposes of private study or research, no
Part may be reproduced without written permission. The content is provided for informational purposes only.