While it's generally held true since the 1960s, Moore's Law – the observation that the number of transistors on a single chip doubles every two years or so – can only last so long. Researchers at Cambridge and the University of Warwick have jumped ahead to its logical endpoint and shrunk wires down to a string of single atoms. Effectively one-dimensional, these "extreme nanowires" are made of tellurium, compressed inside carbon nanotubes to keep them stable.
In our three-dimensional universe (or four, if you count time), it's impossible for a material to be truly 1D or 2D – a sheet of paper still has thickness, no matter how small that may be. But materials like graphene, which is one atom thick but still has height and width, can be functionally two-dimensional. By the same token, the new nanowires are one-dimensional in the sense that they're no wider or taller than an individual atom.
But problems arise on scales this tiny. Atoms don't always behave the way scientists want or expect them to, and without some structure they tend to float apart so the material breaks down. To keep the tellurium atoms in line, the researchers injected them into the center of carbon nanotubes, which hold them together without interfering with their conductivity.
"When working with materials at very small scales such as this, the material of interest typically needs to be deposited onto a surface, but the problem is that these surfaces are normally very reactive," says Paulo Medeiros, first author of the study. "But carbon nanotubes are chemically quite inert, so they help solve one of the problems when trying to create truly one-dimensional materials. However, we're just starting to understand the physics and chemistry of these systems – there's still a lot of basic physics to be uncovered."
The team also found that by altering the diameter of the nanotubes, they could control other properties of the tellurium. The element is normally a semiconductor, but when it's confined that tightly it behaves more like a metal, the researchers found.
Making conductive wires this tiny could help shrink electronic circuits down, cramming more powerful systems into smaller phones, wearables and other devices.
The research was published in the journal ACS Nano.
Source: University of Cambridge
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