A new method to produce large, monolayer single-crystal-like graphene films more than a foot long relies on harnessing a “survival of the fittest” competition among crystals. The novel technique, developed by a team led by the Department of Energy’s Oak Ridge National Laboratory, may open new opportunities for growing the high-quality two-dimensional materials necessary for long-awaited practical applications.
Making thin layers of graphene and other 2D materials on a scale required for research purposes is common, but they must be manufactured on a much larger scale to be useful.
Graphene is touted for its potential of unprecedented strength and high electrical conductivity and can be made through well-known approaches: separating flakes of graphite—the silvery soft material found in pencils—into one-atom-thick layers, or growing it atom by atom on a catalyst from a gaseous precursor until ultrathin layers are formed.
The ORNL-led research team used the latter method—known as chemical vapor deposition, or CVD—but with a twist. In a study published in Nature Materials, they explained how localized control of the CVD process allows evolutionary, or self-selecting, growth under optimal conditions, yielding a large, single-crystal-like sheet of graphene.
“Large single crystals are more mechanically robust and may have higher conductivity,” ORNL lead coauthor Ivan Vlassiouk said. “This is because weaknesses arising from interconnections between individual domains in polycrystalline graphene are eliminated.”
“Our method could be the key not only to improving large-scale production of single-crystal graphene but to other 2D materials as well, which is necessary for their large-scale applications,” he added.
Much like traditional CVD approaches to produce graphene, the researchers sprayed a gaseous mixture of hydrocarbon precursor molecules onto a metallic, polycrystalline foil. However, they carefully controlled the local deposition of the hydrocarbon molecules, bringing them directly to the edge of the emerging graphene film. As the substrate moved underneath, the carbon atoms continuously assembled as a single crystal of graphene up to a foot in length.
“The unencumbered single-crystal-like graphene growth can go almost continuously, as a roll-to-roll and beyond the foot-long samples demonstrated here,” said Sergei Smirnov, coauthor and New Mexico State University professor.
As the hydrocarbons touch down the hot catalyst foil, they form clusters of carbon atoms that grow over time into larger domains until coalescing to cover the whole substrate. The team previously found that at sufficiently high temperatures, the carbon atoms of graphene did not correlate, or mirror, the substrate’s atoms, allowing for nonepitaxial crystalline growth.
Since the concentration of the gas mixture strongly influences how quickly the single crystal grows, supplying the hydrocarbon precursor near the existing edge of single graphene crystal can promote its growth more effectively than the formation of new clusters.
“In such a controlled environment, the fastest-growing orientation of graphene crystals overwhelms the others and gets ‘evolutionarily selected’ into a single crystal, even on a polycrystalline substrate, without having to match the substrate’s orientation, which usually happens with standard epitaxial growth,” Smirnov said.
They found that to ensure optimal growth, it was necessary to create a “wind” that helps to eliminate the cluster formations. “It was imperative that we create an environment where the formation of new clusters ahead of the growth front was totally suppressed, and enlargement of just the growing edge of the large graphene crystal was not hindered,” Vlassiouk said. “Then, and only then, nothing stands in the way of the ‘fittest’ crystalline growth when the substrate is moving.”
The team’s theoreticians, led by coauthor Rice University professor Boris Yakobson, provided a model explaining which crystal orientations possess the unique properties that make them fittest in the run for survival, and why the choice of a winner may depend on the substrate and the precursors.
“If graphene or any 2D material ever advances to industrial scale, this approach will be pivotal, similar to Czochralski’s method for silicon.” Yakobson said. “Manufacturers can rest assured that when a large, wafer-size raw layer is cut for any device fabrication, each resulting piece will be a quality monocrystal. This potentially huge, impactful role motivates us to explore theoretical principles to be as clear as possible.”
Practical scaling up of graphene using the team’s method remains to be seen, but the researchers believe their evolutionary selection single-crystal growth method could also be applied to promising alternative 2D materials such as boron nitride, also known as “white graphene,” and molybdenum disulfide.
The Latest on: Scalable 2D materials
via Google News
The Latest on: Scalable 2D materials
- 2D magnetic insulator makes electrically switchable spin-FET on April 16, 2019 at 10:26 am
Researchers at Cornell University in the US have now succeeded in fabricating a new spin tunnel field-effect transistor (TFET) from a 2D van der Waals material that can be ... which will allow for a ... […]
- Casting New Light on Killer Applications on April 9, 2019 at 1:07 pm
If there’s one constant throughout my career in both 2D and 3D printing ... approximately 1.4 kilograms of material goes in the waste bin. With additive manufacturing, the parts comes out ... […]
- Photo-induced ultrafast active ion transport through graphene oxide membranes on April 8, 2019 at 7:08 pm
Sub-nanometer scale integration of atomically-thin 2D materials enables fabrication of highly compact ... their photo-responsiveness can be further extended for scalable and more precise applications ... […]
- Bring life to your surface on April 2, 2019 at 5:10 pm
For a product or application we are the one-stop-shop for the development of scalable printing processes ... size or weight as well as bringing new functions to (flexible and formable) 2D/3D surfaces ... […]
- 2D Material with Optically Addressable Spin Defects Shows Promise as Host for Quantum Emitters on February 12, 2019 at 4:00 pm
Researchers at Stevens Institute of Technology and Columbia University have developed a scalable, precise method for creating ... Could Aid Next-Gen Biosensors Atom-flat sensors, made from 2D ... […]
- Can 2D materials contribute to consumer electronics? on January 22, 2019 at 10:15 pm
The snag is that graphene from most of these more scalable fabrication methods is prone to defects, which although they may not greatly affect the material’s mechanical properties, significantly ... […]
- The Quantum Flagship selects 2D materials to play a key role in quantum technologies on October 29, 2018 at 2:50 pm
Thus, the new European project 2D·SIPC intends to bring a solution to this problem by developing 2-D material on-chip quantum components (single photon emitters, single photon detectors, photonic ... […]
- Efficient and scalable synthesis of highly aligned and compact two-dimensional nanosheet films with record performances on August 28, 2018 at 2:48 am
Atomically thin two-dimensional (2D) materials have attracted tremendous interests since ... Moreover, these methods are not suitable for scalable production in terms of either time consuming, ... […]
- EFRI 2-DARE: Scalable Synthesis of 2D Layered Materials for Large Area Flexible Thin Film Electronics on July 30, 2018 at 5:00 pm
This project will research an approach for assembling electronics-grade, continuous films of two-dimensional layered materials from nanoplates suspended in liquids. Such a process promises to ... […]
- NEWLIMITS-T3: Advanced Manufacturing & Processing of 2D Materials, Novel Semiconductors & Topological Insulators on May 9, 2018 at 3:19 am
The theme vision is to establish large-scale synthesis of 2D transition metal dichalcogenides ... semiconductors and novel materials using selective deposition and processing. The goals include: ... […]
via Bing News