Technique is moving towards producing solar cells within the next two years

Will circuits of the future be grown on gold?  That's what Lars Samuelson, Professor of Semiconductor Physics at Lund University, Sweden believes.  He's devised an unusual process for semiconductor fabrication that's turning heads in the chipmaking world.

He recalls in a press release, "When I first suggested the idea of getting rid of the [silicon] substrate, people around me said 'you're out of your mind, Lars; that would never work'. When we tested the principle in one of our converted ovens at 400°C, the results were better than we could have dreamt of."

Most circuits are grown via techniques like vapor deposition with crystals of different chemistry being deposited on a wafer substrate of polycrystalline silicon.  Professor Samuelson's method also uses gas deposition, but it throws out the traditional substrate, instead using gold nanoparticles suspended in the flowing gas.  Nanoscopic semiconductor structures grow via deposition on the gold nanoparticle.  The finished structures then float into later ovens for curing.

"The basic idea was to let nanoparticles of gold serve as a substrate from which the semiconductors grow", Professor Samuelson describes, "This means that the accepted concepts really were turned upside down!"

Nanowire production
Nanoparticles grow through ovens, growing nanowires via vapor deposition.
[Image Source: Nature]

Currently, the method is growing standard conductive nanowires -- tiny strands of semiconductor that can be mere atoms thick -- but they hope to eventually extend the method to produce special kinds of nanowires, such as wires that act as p-n diodes.

At this point you may be thinking, "Great, but how are these nanowires going to form a circuit?"

That's an excellent question, and admittedly a drawback to this novel form of fabrication of circuit components -- after formation, the completed components must be somehow self-assembled into a structure.  Professor Samuelson is currently working with fellow Lund University researchers to use a type of epitaxy process called "aerotaxy", which prompts nanorods to undergo directed self-assembly into circuit structures.

Thin film solar
The university hopes to produce solar panels with the new technique within two years.
[Image Source: EnergyInformative]

The university says that the process could one day be commercialized to form "energy-saving solar cells, LEDs, batteries and other electrical equipment that is now an integrated part of our lives."

Professor Samuelson hopes to have a prototype of the solar-cell circuit production process done in the next two years, and then move on to other circuit types.

His work has been published in a paper in the prestigious peer-reviewed journal Nature.  Other authors on the paper include Magnus Heurlin, David Lindgren, Martin Ek, Reine Wallenberg, and Knut Deppert -- all Lund University researchers or faculty -- and Martin Magnusson of Sol Voltaics AB, a solar startup that hopes to help Professor Samuelson commercialize his technique. 

Sources: Nature, Lund University [press release]

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