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Atomic-scale solutions for Microsoft

In the push for ever smaller and faster computer chips, Microsoft has funded researchers using Microscopy Australia’s facility at the University of Sydney to help to understand the behaviour of a potential new type of material for making computer chips.

Silicon, which has been used since the beginning of modern computing, is currently etched into layers of interconnecting silicon nanowires processed so that electrons only need to travel approximately three nanometres to carry signals around the chip. As this is the thickness of only a few atoms, there is hardly any room left to manoeuvre: silicon chips have hit a limit.

To overcome this problem, new materials are being explored. One of these is indium arsenide (InAs). Even though indium and arsenic atoms are larger than silicon atoms, electrons can flow faster through InAs than through silicon.

Research collaborators in Denmark have grown nanowires made of InAs. These need to be grown on top of an indium gallium arsenide (InGaAs) core. One tricky issue is that at the high temperatures used to grow the nanowires, indium and gallium diffuse easily. When the gallium diffuses into the outer InAs layer, it compromises the purity of that layer, reducing its electron carrying capacity. Microsoft wanted to know how they can visualise the extent of that diffusion.

By using atom probe tomography and atomic-resolution transmission electron microscopy at the University of Sydney, the researchers were able to accurately measure how much diffusion had occurred during nanowire growth and therefore help inform the design of these nanowires into the future.

Ref. Jiangtao et al. 2022, Applied Materials & Interfaces,

TEM image of a nanowire showing an InAs layer grown on an inGaAs core.