April 05, 2014
In the past, researchers have found that multi-crystal synthesis – the process of synthesising small graphene particles to produce large-area graphene – deteriorated the electric and mechanical properties of the material, limiting its application range and making it difficult to commercialise.
The new method involves synthesising large-area graphene into a single crystal on a semiconductor, while maintaining its electric and mechanical properties. By developing a method for growing a single crystal graphene into a large area, the researchers claim they could displace the tech industry’s reliance on silicon.
"This is one of the most significant breakthroughs in graphene research in history,” said the laboratory leaders at SAIT’s Lab. “We expect this discovery to accelerate the commercialisation of graphene, which could unlock the next era of consumer electronic technology."
Science - Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium
ABSTRACT
The uniform growth of single-crystal graphene over wafer-scale areas remains a challenge in the commercial-level manufacturability of various electronic, photonic, mechanical, and other devices based on graphene. Here, we describe wafer-scale growth of wrinkle-free single-crystal monolayer graphene on silicon wafer using a hydrogen-terminated germanium buffer layer. The anisotropic twofold symmetry of the germanium (110) surface allowed unidirectional alignment of multiple seeds, which were merged to uniform single-crystal graphene with predefined orientation. Furthermore, the weak interaction between graphene and underlying hydrogen-terminated germanium surface enabled the facile etch-free dry transfer of graphene and the recycling of the germanium substrate for continual graphene growth.
21 pages of supplemental material
So, we now have had at least 3 teams in the last 12 months announce
solutions to the grain boundary problems of graphene CVD sheets. There
is the Columbia Engineering group last May 31, IIRC, who said they'd
found an etchant for removing the copper substrate that left the sheet
of graphene 90% as strong in tension as a single crystalline grain is,
at 180 times the tensile strength of Steel, instead of 200 times. There
is the group that found they could anneal the copper substrate for
graphene deposition so that the crystal sizes of the copper substrate
were much larger, giving larger far larger graphene crystals. Now, we
have a Samsung group saying that they can use thermal release tape to
remove the substrates.
I am awaiting the combination of one or more of these methods with the work by Dr. Greer's Caltech group and their 3d nano-architectured materials.
http://www.jrgreer.caltech.edu...
We already have heard that a graphene sheet can be a base from which to grow vertically aligned 3d carbon nanotubes. It seems the nano-lattices the Greer Group is making should be doable with graphene, even using copper substrates deposited on their original plastic lattice. Lastly, there are recent reports of starting with multilayered graphene sheets, adding excess hydrogen to the atmosphere in which they grow, and seeing those multiple sheets transform into well-ordered diamond crystalline sheets, without high pressures. If this can be added to the above, then a composite graphene/diamond 3d nano-architectured material could have the toughness of high tensile strength graphene reinforcement inside a stiff diamond matrix, ...all as the basic material for the nano-lattice structured materials the Greer Group has been speaking about.
This would allow many good things to be built, such as SSTO vehicles light enough that when they re-enter they could float in the lower atmosphere until they compress enough air for ballast to bring them to ground, and figurative "cloud-castles" in the sky, to live in. However, it would also make the use of in situ resources in Space more economical more quickly. We could haul in 10s of thousands of tons of asteroid material in the next several decades.
Still, with the above technology combinations we could build structures equal to what we would build here today with 100s of thousands of tons of materials, using a few hundred tons of raw asteroid material. It is not at all impossible that the atmospheres it holds in Space would be the majority of the mass of a habitat. This would seem to shift the emphasis at the start of asteroid mining from finding huge amounts of asteroid materials to processing smaller amounts of them to make the easily obtained small amounts into what we want for the first several decades. Far lower capital costs that way!
I am awaiting the combination of one or more of these methods with the work by Dr. Greer's Caltech group and their 3d nano-architectured materials.
http://www.jrgreer.caltech.edu...
We already have heard that a graphene sheet can be a base from which to grow vertically aligned 3d carbon nanotubes. It seems the nano-lattices the Greer Group is making should be doable with graphene, even using copper substrates deposited on their original plastic lattice. Lastly, there are recent reports of starting with multilayered graphene sheets, adding excess hydrogen to the atmosphere in which they grow, and seeing those multiple sheets transform into well-ordered diamond crystalline sheets, without high pressures. If this can be added to the above, then a composite graphene/diamond 3d nano-architectured material could have the toughness of high tensile strength graphene reinforcement inside a stiff diamond matrix, ...all as the basic material for the nano-lattice structured materials the Greer Group has been speaking about.
This would allow many good things to be built, such as SSTO vehicles light enough that when they re-enter they could float in the lower atmosphere until they compress enough air for ballast to bring them to ground, and figurative "cloud-castles" in the sky, to live in. However, it would also make the use of in situ resources in Space more economical more quickly. We could haul in 10s of thousands of tons of asteroid material in the next several decades.
Still, with the above technology combinations we could build structures equal to what we would build here today with 100s of thousands of tons of materials, using a few hundred tons of raw asteroid material. It is not at all impossible that the atmospheres it holds in Space would be the majority of the mass of a habitat. This would seem to shift the emphasis at the start of asteroid mining from finding huge amounts of asteroid materials to processing smaller amounts of them to make the easily obtained small amounts into what we want for the first several decades. Far lower capital costs that way!
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