2D goes 3D
If you are reading this blog, you probably already think that 2D materials are awesome. However, stacks combining several 2D materials could be even better — they open almost endless possibilities for new properties and devices, as they draw from a wide library of 2D materials with different electronic properties, ranging from insulating to metallic, conductive and superconductive, which can be mixed and matched to create hybrid structures with unique functionalities. Xiangfeng Duan and colleagues bring us on an inspiring journey to discover van der Waals heterostructures in a newly published Review in Nature Reviews Materials. Flexible and transparent electronic and optoelectronic devices based on van der Waals stacks have already been demonstrated, including tunneling transistors, vertical field-effect transistors, wearable electronics and innovative solar cells.
The ‘ingredients’ for the heterostructures feature graphene as the most common component, but they can also include boron nitride, transition metal dichalcogenides, phosphorene and other materials. Thanks to the fact that the interlayer interactions are van der Waals in nature, highly disparate materials can be integrated without limitations imposed, for example, by lattice mismatches. Because all the components of a device can be integrated in a single membrane without needing to incorporate a substrate, flexible and adaptable devices can be obtained.
There are still important challenges that lie ahead; namely, the difficulty of developing fabrication methods that are both scalable and precise, and the need to produce reliable contacts. But van der Waals heterostructures promise to enable amazing functionalities in electronic and optoelectronic devices — maybe it is this growth in the third dimension that will realize the full potential of 2D materials.
Giulia Pacchioni (Nature Reviews Materials)