Carbon-based transistors take a big step forward

Transistors based on carbon instead of silicon can bring faster speeds to computers and drastically reduce power consumption (think of a mobile phone that can hold power for months), but from the current point of view, building an effective carbon-based circuit requires The toolset is still incomplete
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The team of chemists and physicists at the University of California at Berkeley finally created the last tool in the toolbox, a metal wire made entirely of carbon, which laid the foundation for further research to build carbon-based transistors
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Felix Fischer, professor of chemistry at the University of California, Berkeley, said: “Integrating this technology together is in the field of carbon fiber materials, staying in the same material.
” He pointed out that the ability to make all circuit components with the same material can make Come out, and more relaxed
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"This is one of the key things missing in the overall carbon-based integrated circuit architecture
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" Felix Fischer emphasized? Metal wires (such as metal channels used to connect transistors in computer chips) transport electrons from one device to another.
, And interconnect the semiconductor elements in transistors (the building blocks of computers)
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The UC Berkeley team has been working on how to use graphene nanoribbons to make semiconductors and insulators.
Graphene nanoribbons are one-dimensional narrow graphene ribbons that are only one atom thick.
This structure Composed entirely of carbon atoms, arranged in a hexagonal shape connected to each other, similar to a chicken thread
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? The new carbon-based metal is also graphene nanoribbons, but the design should pay attention to the conductive electrons between the semiconductor nanoribbons in the all-carbon transistor
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Fischer’s colleague Michael Crommie, a professor of physics at the University of California, Berkeley, said that metal nanoribbons are assembled from smaller, identical building blocks, using a bottom-up approach
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Each structural unit contributes an electron, which can flow freely along the nanobelt
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? Although other carbon-based materials (such as expanded 2D graphene and carbon nanotube sheets) can be metallic, they also have problems
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For example, remodeling 2D graphene sheets into nano-scale strips can spontaneously turn them into semiconductors or even insulators
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Carbon nanotubes are excellent conductors and cannot be produced in large quantities with the same precision and repeatability as nanobelts
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? Crommie said: "Nanobelts allow us to chemically access various structures using a bottom-up approach, which nanotubes have not yet been able to do
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" "This allows us to basically stitch together electrons to create metallic nanoribbons.
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Which has not been done before .
This is one of the major challenges in the field of graphene nanoribbons technology, and it is why we are so excited about it
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"? Metallic graphene nanoribbons (featured by a wide, partially filled metal electronic band) ) It has a conductivity comparable to that of 2D graphene itself
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? We believe that the metal wire is indeed a breakthrough; Fischer added that this is the first time we have deliberately used carbon-based materials to intentionally create an ultra-narrow metal conductor-a good intrinsic conductor
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• Crommie, Fischer and colleagues of the University of California, Berkeley and Lawrence Berkeley National Laboratory (Berkeley Lab) will publish their findings in the September 25 issue of Science
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? Adjust the topology? According to Moore's Law, silicon-based integrated circuits have been empowering computers for decades, and their speed and performance are constantly improving, but they have reached the speed limit-that is, they can be between zero and one.
The speed of switching
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Reducing power consumption has also become more and more difficult
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Computers have consumed a large part of the world's energy production
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Fischer said that carbon-based computers can switch many times faster than silicon computers and consume only a small amount of power
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? Graphene is pure carbon and is the main competitor for these next-generation carbon-based computers
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Narrowband graphenes are mainly semiconductors.
However, the challenge is to make them act as both insulators and metal (on the contrary, completely non-conductive and completely conductive respectively) insulators and metals, so that transistors and processors are made entirely of carbon
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? A few years ago, Fischer and Crommmie collaborated with Physics professor at the University of California at Berkeley and theoretical materials scientist Steven Louie to discover a new way to connect small-length nanoribbons to reliably create the entire conductive property domain
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? Two years ago, the team proved that by correctly connecting the short segments of the nanoribbon, the electrons in each segment can be arranged into a new topological state (a special quantum wave function), resulting in tunable semiconductor properties
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In this new work, they used a similar technique to stitch together short sections of nanoribbons to create a conductive metal wire tens of nanometers long and only a few nanometers wide
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? Nanobelts are chemically produced and are imaged on a very flat surface using a scanning tunneling microscope
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Simple heating can cause the molecules to react chemically and bind together in the right way
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Fischer compared the assembly of daisy chain building blocks with a set of Lego toys, but the design of Lego toys is suitable for atomic level
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"They are all precisely designed, so they can only be assembled in one way
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It's like you hold a bag of Lego toys, then shake it, and you come out with a fully assembled car," he said
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"This is the magic of chemically controlling self-assembly
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" After the assembly is complete, the electronic state of the new nanoribbon is a metal.
As Louie predicted, each part contributes a conductive electron
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? The final breakthrough can be attributed to the small changes in the nanoribbon structure
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? "Using chemistry, we have produced a small change, that is, only one chemical bond in every 100 atoms has changed, but this has increased the metallicity of the nanoribbons by 20 times.
From a practical point of view, this is very important.
It becomes a very good metal," Cromi said
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The two researchers are collaborating with electrical engineers at the University of California, Berkeley, to assemble their toolboxes of semiconductor, insulating, and metallic graphene nanoribbons into working transistors
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? Fischer said: "I believe this technology will change the way we build integrated circuits in the future", "This should allow us to significantly improve the best performance than can be expected
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We now have a lower Power consumption is the way to achieve faster switching speeds
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This is the reason why the carbon-based electronic semiconductor industry will be promoted in the future
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