First natural van der Waals heterostructure exfoliated

(Nanowerk News) Scientists at The University of Manchester have ‘re-discovered’ a material, which could make the construction of 2D van der Waals heterostructures easier to build.
Franckeite naturally stacks into 2D sheets
Franckeite naturally stacks into 2D sheets. (Image: University of Manchester)
Graphene was the world’s first two-dimensional material isolated in 2004 at The University of Manchester, it is 200 times stronger than steel, lightweight, flexible and more conductive than copper.
Since then a whole family of other 2D materials have been discovered and continues to grow.
Using graphene and other 2D materials, scientists can layer these materials, similar to stacking bricks of Lego in a precisely chosen sequence known as van der Waals heterostructures to create high-performance structures tailored to a specific purpose.
One of the challenges when creating these heterostuctures is the painstaking stacking of the individual components on top of each other.
However, as reported in Nature Communications ("Exfoliation of natural van der Waals heterostructures to a single cell thickness"), a team supervised by Professor Robert Dryfe have discovered that franckeite (a mixed-metal sulphide mineral first discovered in 1893) naturally stacks into 2D sheets.
This results in van der Waals heterostructures, which can be exfoliated down to a single layer using simple scotch-tape mechanical exfoliation- the method used to isolate graphene.
Importantly, this behaviour is likely to be common in a wider family of materials and could be exploited as an alternative to artificial stacking of two-dimensional materials.
Franckeite also opens us new possibilities for energy storage applications such as solar energy and supercapacitors due to its excellent electrical conductivity and remarkable electrochemical properties.
Research Associate Matej Velicky who led the experimental work said “We believe that this work will be followed by further studies of other natural van der Waals heterostructures and that the results will accelerate progress in the emerging “bottom-up” chemical synthesis of such complex structures”.
Prof Robert Dryfe said, “This work is a perfect demonstration of the continual surprises that are revealed through the study of 2D materials”.
Source: University of Manchester