3rd May 2018
New material offers 50 times greater current density than conventional copper
Engineers at the University of California, Riverside, have demonstrated prototype devices made of an exotic material able to conduct a current density 50 times greater than conventional copper interconnect technology.
Current density is the amount of electrical current per cross-sectional area at a given point. As transistors in integrated circuits become smaller and smaller, they need higher and higher current densities to perform at the desired level. Most conventional electrical conductors, such as copper, tend to break due to overheating or other factors at high current densities, presenting a barrier to creating increasingly small components. The electronics industry needs alternatives to silicon and copper that can sustain extremely high current densities at sizes of just a few nanometres.
The advent of graphene has resulted in a massive, worldwide effort to find other two-dimensional, or 2D, layered materials that could meet the need for nanoscale electronic components able to sustain a high current density. While 2D materials consist of a single layer of atoms, 1D materials consist of individual chains of atoms, weakly bound to one another – but their potential for electronics has not been as widely studied. One can think of 2D materials as like thin slices of bread, while 1D materials are like spaghetti. Compared to 1D materials, 2D materials seem huge.
Now, researchers at UC Riverside have discovered that nanoribbons made of zirconium tritelluride, or ZrTe3, have an exceptionally high current density that far exceeds any conventional metals like copper. The team's breakthrough could help to push research from 2D to 1D materials – an important advance for the future generation of electronics.
“Conventional metals are polycrystalline. They have grain boundaries and surface roughness, which scatter electrons,” explains Alexander A. Balandin, distinguished professor of electrical and computer engineering, who led the work. “Quasi-one-dimensional materials, such as ZrTe3, consist of single-crystal atomic chains in one direction. They do not have grain boundaries and often have atomically smooth surfaces after exfoliation. We attributed the exceptionally high current density in ZrTe3 to the single-crystal nature of quasi-1D materials.”
These new materials could be grown directly into nanowires, with a cross-section that corresponds to an individual atomic chain, the team says. The level of current they observed for ZrTe3 was higher than reported for any metals or other 1D materials.
Electronic devices depend on special wiring to carry information between different parts of a circuit or system. As developers continue to shrink devices with each passing year, the internal parts must also become smaller, and the interconnects that carry information between parts must become smallest of all. Depending on how they are configured, ZrTe3 nanoribbons could form either nanometre-scale local interconnects, or device channels for components of the tiniest devices.
The UC Riverside group’s experiments were conducted with nanoribbons sliced from a pre-made sheet of material. Industrial applications need to grow nanoribbon directly on the wafer. This manufacturing process is already under development, and Prof. Balandin believes that 1D nanomaterials hold real possibilities for applications in future electronics: “The most exciting thing about the quasi-1D materials is that they can be truly synthesised into the channels or interconnects with the ultimately small cross-section of one atomic thread – approximately one nanometre by one nanometre.”
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