By Josh Perry, Editor
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Scientists at the Swiss Federal Institute of Technology in Lausanne (EPFL) found a method for controlling and standardizing the production of nanowires on silicon surfaces, which could enable new optical functionality to electronic chips.

Researchers have found a way to control the production of nanowires on silicon.
(Jamani Caillet/EPFL)

According to a report from the EPFL, this study provided a new understanding for what happens at the start of nanowire growth, which allowed researchers to make the process fully controlled and reproducible.

“The standard process for producing nanowires is to make tiny holes in silicon monoxide and fill them with a nanodrop of liquid gallium,” the article explained. “This substance then solidifies when it comes into contact with arsenic. But with this process, the substance tends to harden at the corners of the nanoholes, which means that the angle at which the nanowires will grow can’t be predicted. The search was on for a way to produce homogeneous nanowires and control their position.”

EPFL researchers focused on the ratio of diameter to height in the hole. When the correct ratio is reached, a substance forms on the ring on the edge of the hole, preventing the nanowires from growing at odd angles.

The research was recently published in Nature Communications. The abstract read:

“III-V semiconductor nanowires deterministically placed on top of silicon electronic platform would open many avenues in silicon-based photonics, quantum technologies and energy harvesting. For this to become a reality, gold-free site-selected growth is necessary.

“Here, we propose a mechanism which gives a clear route for maximizing the nanowire yield in the self-catalyzed growth fashion. It is widely accepted that growth of nanowires occurs on a layer-by-layer basis, starting at the triple-phase line.

“Contrary to common understanding, we find that vertical growth of nanowires starts at the oxide-substrate line interface, forming a ring-like structure several layers thick. This is granted by optimizing the diameter/height aspect ratio and cylindrical symmetry of holes, which impacts the diffusion flux of the group V element through the well-positioned group III droplet.

“This work provides clear grounds for realistic integration of III-Vs on silicon and for the organized growth of nanowires in other material systems.”