Engineers from MIT have developed a technique to fabricate ultra-thin semiconducting films made from a host of exotic materials other than silicon.
The new technique, researchers say, will provide a cost-effective method to fabricate flexible electronics made from any combination of semiconducting elements, that could perform better than current silicon-based devices.
People have mostly used silicon wafers because they're cheap
To demonstrate their technique, the researchers fabricated flexible films made from gallium arsenide, gallium nitride, and lithium fluoride. These are materials that exhibit better performance than silicon but until now have been prohibitively expensive to produce in functional devices.
"We've opened up a way to make flexible electronics with so many different material systems other than silicon," says Jeehwan Kim, career development associate professor in the departments of Mechanical Engineering and Materials Science and Engineering.
Kim envisions the technique can be used to manufacture low-cost, high-performance devices such as flexible solar cells, and wearable computers and sensors.
We've opened up a way to make flexible electronics with so many different material systems other than silicon
The researchers tested their hypothesis by using remote epitaxy to copy semiconducting materials with various degrees of polarity, from neutral silicon and germanium, to slightly polarised gallium arsenide, and finally, highly polarized lithium fluoride - a better, more expensive semiconductor than silicon.
They found that the greater the degree of polarity, the stronger the atomic interaction, even, in some cases, through multiple sheets of graphene. Each film they were able to produce was flexible and merely tens to hundreds of nanometers thick.
With this new understanding, he said that researchers can now simply look at the periodic table and pick two elements of opposite charge. Once they acquire or fabricate a main wafer made from the same elements, they can then apply the team's remote epitaxy techniques to fabricate multiple, exact copies of the original wafer.
"People have mostly used silicon wafers because they're cheap," Kim said.
Researchers can now simply look at the periodic table and pick two elements of opposite charge
"Now our method opens up a way to use higher-performing, non-silicon materials. You can just purchase one expensive wafer and copy it over and over again, and keep reusing the wafer. And now the material library for this technique is totally expanded."
The scientists believe that this remote epitaxy could be used to fabricate ultra-thin, flexible films from a wide variety of previously exotic, semiconducting materials - as long as the materials are made from atoms with a degree of polarity.
Such ultra-thin films could potentially be stacked, one on top of the other, to produce tiny, flexible, multifunctional devices, such as wearable sensors, flexible solar cells, and even, in the distant future, 'cellphones that attach to your skin'.
"In smart cities, where we might want to put small computers everywhere, we would need low power, highly sensitive computing and sensing devices, made from better materials," Kim added. "This unlocks the pathway to those devices."
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