The applications of 2D materials are numerous and diverse, ranging from electronics to catalysis, and from information storage to medicine.

A Focus Issue just published in Nature Reviews Materials covers the synthesis and fundamental properties of several 2D materials, as well as the devices they enable, combining Reviews, Comments and Research Highlights. In particular, a Review by Manish Chhowalla explores the use
of graphene, hexagonal boron nitride, transition metal dichalcogenides (TMDCs), phosphorene and silicene as channels in field-effect transistors. The emerging field of valleytronics and its implementation in graphene and TMDCs is the topic of a Review by John Schaibley, Xiaodong Xu and colleagues. Beyond electronics, graphene (and, more in general, carbon-based materials) is attracting growing interest as a low-cost catalyst for renewable energy production and storage: the use of heteroatom-doped graphene as a metal-free catalyst is the topic of a Review by Xien Liu and Liming Dai. In another Review, by Castro Neto and colleagues, the synthesis, properties and applications of phosphorene are discussed.

There is clearly a lot of fundamental research being carried out on 2D materials; however, it is also necessary to address their translation into commercial or medical devices. This problem is analyzed in two Comments, one by Seongjun Park and one by Kostas Kostarelos. A common theme emerging from these opinion pieces is the need for stronger collaboration between academia and industry or medical professionals.

As it was argued in other posts in this blog, the road to the commercialization of 2D-materials-based products is still long, and many challenges lie ahead. But numerous exciting developments in the field of 2D materials are keeping researchers busy, and we hope that the overview provided in this Focus Issue will be a useful tool for the community to explore them.

Giulia Pacchioni (Nature Reviews Materials)

The commercialization of graphene-based products is a recurring theme in this blog. Why after much talking about graphene being a wonder material the most high-tech graphene-based product we can buy is still a tennis racket? Nature Reviews Materials asked this question to Seongjun Park, an engineer working in Samsung and studying graphene. In a Comment piece, he reminded the readers that the commercialization of new materials and technologies always takes time, often decades — optical memory devices and phase-change memories are good examples, as it took more than 30 years to take them to the market. Compared to them, graphene is still a young technology: it is only 12 years that scientists and engineers are playing with it and tweaking its properties.

Park likens the process of commercialization to a jigsaw puzzle, in which many pieces need to fit together in order to produce a recognizable image. Many studies are carried out on graphene, but they often focus on one specific property, whereas for creating a graphene-based device multiple properties have to be optimized at the same time, and multiple engineering challenges have to be addressed. Currently, two types of applications are under development: those that are easy to develop and promise low reward, and those that are very challenging but are potential game-changers. The way to go, Park reckons, is to develop the first kind of products while we wait for the second kind to mature. One factor that is slowing down the process of graphene commercialization is the fact that academics tend to focus on research lines that are likely to lead to high-profile publications, expecting engineers in industry to develop commercial products on their own; papers reporting results from industry are often judged incremental and of little interest. A stronger link between academia and industry is thus needed to speed up graphene commercialization.

It is often said that in the Gartner hype cycle graphene has passed the peak of inflated expectations. Now is time to take a more realistic approach to what researchers and engineers can develop in the short term. It is very early to lose faith in the potential of graphene to enable new, revolutionary products.

Giulia Pacchioni (Nature Reviews Materials)

Two-dimensional layered materials and van der Waals heterostructures. From Nature Reviews Materials 16042 (2016) “Van der Waals heterostructures and devices“

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)