Transistors based on carbon instead of silicon can potentially increase the speed of a computer by more than 1,000 times and reduce its power consumption by more than a thousand times. For example, a cell phone can be charged once for several months, but it is required to build an effective carbon circuit The tools and means have not been complete.
A team of chemists and physicists at the University of California, Berkeley, finally created the last necessary means in this toolbox, which is a conductive wire made entirely of carbon, laying the foundation for further research to build carbon-based transistors, and Ultimately it is the computer.
Felix Fischer, a professor in the Department of Chemistry at the University of California, Berkeley, said: "Integrating this technology together is to maintain the same materials in the field of carbon fiber materials." The same material is used to make all circuit components. Ability can be made easier. "This has always been one of the key factors missing in the overall picture of the all-carbon-based integrated circuit architecture."
Wires, such as metal conductors used to connect transistors in computer chips, can pass current between devices and connect the semiconductor components in the transistors, that is, the components of the computer.
The research team has worked on how to use graphene nanoribbons to make semiconductors and insulators. Graphene nanoribbons (GNR) are one-dimensional, atom-thick graphene ribbons. This structure is composed entirely of carbon atoms, arranged to be connected to each other. Hexagons.
The structure of graphene nanoribbons has high electrical conductivity, high thermal conductivity, and low noise. These excellent qualities have promoted graphene nanoribbons to become another choice for integrated circuit interconnect materials, which may replace copper metal.
The new carbon-based is graphene nanoribbons, but the design should pay attention to the conductive electrons between the semiconductor nanoribbons in the all-carbon transistor. The researchers say that Daodian nanoribbons are assembled by assembling them from smaller, identical building blocks: a bottom-up approach. Each structural unit contributes an electron, which can flow freely along the nanobelt.
Although other carbon-based materials, such as graphene and two-dimensional expansion plates of carbon nanotubes, can be used as wires, they have problems. For example, remodeling 2D graphene sheets into nano-scale strips can spontaneously turn them into semiconductors or even insulators. Carbon nanotubes are excellent conductors and cannot be produced in large quantities with the same precision and repeatability as nanobelts.
The researchers said: "Nanobelts allow us to use bottom-up manufacturing methods to chemically contact a variety of structures, and nanotubes have not been able to do this." "This allows us to basically stitch electrons in Together to create conductive nanoribbons, which has not been done before. This is one of the major challenges in the field of graphene nanoribbons technology, which is why we are so excited about it."
Graphene nanoribbons have the characteristics of wide, partially filled metal electronic bands, which are comparable to the conductivity of 2D graphene itself. "We believe that carbon wire is indeed a breakthrough; this is the first time we have deliberately used carbon-based materials to make an ultra-narrow conductor, a good intrinsic conductor, without external doping."
Scanning tunneling microscope image of broadband graphene nanoribbons. Each protruding cluster corresponds to a single occupied electron orbit. The formation of pentagonal rings near each cluster will increase the conductivity of graphene nanoribbons by more than ten times. The width of the graphene nanoribbons backbone is 1.6 nanometers.
Adjust the topology
According to Moore's Law, silicon-based integrated circuits have been serving computers for decades, and their speed and performance are constantly improving, but they have reached the speed limit and reducing power consumption has become increasingly difficult. Computers have consumed a large part of the world's energy production. The switching speed of a carbon-based computer can be many times faster than that of a silicon computer and consumes only a small amount of power.
Graphene is pure carbon and is the main competitor for these next-generation carbon-based computers. Narrowband graphenes are mainly semiconductors. However, the challenge is to make them also used as insulators and conductors to form transistors and processors entirely from carbon.
A few years ago, the research team discovered a new way to connect small-length nanoribbons, thereby reliably creating the entire conductive property domain. Two years ago, the team demonstrated 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.
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.
The nanoribbons are produced chemically and are imaged on a very flat surface using a scanning tunneling microscope. Simple heating is used to induce chemical reactions between molecules and bind them together in the right way. Researchers compare the assembly of daisy-chain building blocks to Lego toys, but this is a Lego toy designed for atomic level.
"They are all precisely designed, so they can only be assembled in one way. It's as if you hold a bag of Lego toys, then shake it, and then you have a fully assembled car." "This It is to use chemical methods to control the magic of self-assembly." After the assembly is completed, the electronic state of the new nanoribbon is a kind of conductor, and each part contributes a conductive electron.
The final breakthrough can be attributed to the small changes in the nanoribbon structure. "Through chemistry, we have made a small change, that is, only one chemical bond in every 100 atoms changes, but this has increased the metallicity of the nanoribbons by 20 times. From a practical point of view, this is very important to make it Has become a very good conductor."