Big things have small beginnings. Cutting-edge water filtration technology that could save the lives of millions still requires atomically thin layers of graphene, just as a powerful method for destroying antibiotic-resistant bacteria needs incredibly tiny “quantum dots”.
Nanoengineers, then, are basically wizards, and a new paper – published in Science – does little to dampen that image. A team of material manipulators from Cornell University and the University of Chicago have apparently pioneered a way to merge two segments of crystals together at an atomic level. Although this is compared to how we’d sew fabric together, it's more like watching two blobs of magnetic fluid jump toward each other.
And though you may think that sowing together lattices merely three atoms thick is simply showing off, it actually brings with it a myriad of benefits. As noted in a press release accompanying the study, electronic equipment of all kinds – from LEDs to chips in supercomputers – require as smooth, unbroken, and seamless connections as possible to allow for the effortless flow of electrons between the two.
This isn’t as easy as it sounds. These lattices of electronically conductive material aren’t always perfectly arranged, which means you’re not really piecing them together like matching jigsaw pieces. It’s more like trying to piece together imperfectly shattered pieces of glass – you may get a connection, but there are gaps and dents that’ll cause problems.
The primary problem emerges from the fact that the materials forming these vital connections are grown independently – via a process known as epitaxy – and, often, at different, staccato, stop-start rates. In order to circumvent this problem, the team decided to try out omnidirectional epitaxy, wherein they’d grow the crystal lattices simultaneously in an uninterrupted way, so that they’d automatically stitch themselves together up as they grew outwards.
As noted in their study, the team succeeded, creating pristine crystal layers that met in the middle to form “coherent, atomically thin superlattices”. This method meant that the beautifully colliding, malleable materials filled in any imperfections as they went along, and ultimately joined up without any gaps or bumps or inconvenient bobbles.
When they threw it into a basic diode circuit, they were understandably thrilled to see the attached LED become illuminated. It’s not a perfect technique, mind you: Their paper notes that when their superlattices were cooled down from their growth temperature of 600°C (1,112°F), thermal expansion and contraction “ripples” were seen to form.
While working on what this nuance means for electronic applications, they might want to conjure up a theory as to why their technique works, and how exactly it grows in the way they observed. As is rather beautifully noted in their study, a theory explaining all the superlattice’s nuances is “currently lacking”.
Everyday’s a school day.