Mar Garcia Hernandez, a researcher at the Institute of Materials Science in Madrid (ICMM), talks to science journalist Anna Demming about her career to date. Garcia Hernandez also comments on the topical review article she recently co-ordinated for the journal 2D Materials about producing and processing graphene and related materials
What is the focus of your own research?
We grow graphene on insulators of technological interest and then explore the nature of the interfaces between the substrates and graphene so as to optimize the electrical properties of the materials we grow. Examples include glass, Si/SiO2 wafers, TiO2, as well as grown layers of 2D transition metal dichalcogenides (TMDs). We are also developing a new platform that will allow us to functionalize 2D materials for various device applications under conditions compatible with the device itself, while preserving the properties of the pristine material. Our main focus is functionalization with biomolecules for biomedical applications.
How did you find yourself working on this field?
I had been working on the growth and characterization of complex perovskite heterostructures for spintronics applications for quite a number of years – in fact I still work in this field now. I was interested in the new physics that these systems reveal at the interfaces, such as the appearance of superconductivity at the interface of two insulating materials or the build-up of magnetism at the interface between non-magnetic materials. So I was familiar with exploring the interfaces between two grown 2D layers and was very much interested in these low-dimensional materials. Then graphene was discovered and shown to be the thinnest known material, as well as exhibiting fascinating electronic transport properties. A new series of free-standing 2D materials started to enlarge the catalogue of interest for 2D flatlands research and presented a feasible path towards the fabrication of different kinds of multifunctional heterostructures of different 2D materials. So I decided to explore these 2D materials with a view to building up heterostructures.
What would you identify as the most important recent achievement for characterization and fabrication of these materials?
There are some very recent results on the growth of hexagonal boron nitride (hBN) on platinum that deserve particular attention as these layers provide nearly perfect crystals that we can then transfer to encapsulate high-quality graphene and meet the requirements of electronic foundries. This is technologically very relevant as there is no way to preserve graphene’s outstanding properties without proper encapsulation.
Is standardization a problem for other 2D materials as it has been for graphene?
Yes indeed, different synthesis routes render materials with very different properties, so standardization is a problem for all 2D materials. The problem will continue until the standardization international bodies establish corresponding standards. This will take a very long time because the procedures have to be non-ambiguous and robust, and these 2D materials are very new. In the meantime, it would be desirable to refer to a good practice code for labelling these materials.
What prompted you to draw up this review for the journal 2D Materials?
The Graphene Flagship has gathered a large set of world-class researchers with outstanding expertise in the synthesis of materials, that attend meetings together and organize workshops to exchange their most recent findings. I saw that there was a great opportunity to offer an overall picture on the synthesis of graphene and other 2D materials to a broader audience and started to lay out a basic scheme for this review.
The review covers synthesis methods for 2D materials, ranging from chemistry routes to ultrahigh vacuum methods. It also tackles the processing and characterization methods suitable for this class of materials. I lead the materials work package in the Graphene Flagship and succeeded in encouraging Flagship partners to send in their contributions. I also attended many other work package meetings to spot other groups working on the synthesis of these materials that were not covered by my own work package, so that I could invite them to contribute. Finally, I contacted other contributors to fill in the gaps for any topics that had not been specifically addressed by the Graphene Flagship. The result is this comprehensive review dealing with many aspects of the synthesis, processing and characterization of these materials.
The scope covers a huge field these days – how did you draw the line over what to include and what not?
We decided to include the topics that could attract a large audience, those that according to the literature have proven to be the most popular and useful. The Graphene Flagship had already targeted most of the hot topics related to the synthesis of 2D materials and this helped a lot. Once the basic content was decided, most of the co-authors knew pretty well how to describe the major findings in their respective fields. Obviously the participation of a large number of people in the writing of the review is only possible at the expense of losing some homogeneity in the coverage.
What would you consider the main outstanding challenge?
One of the main challenges from the view point of synthesis is producing high-quality 2D materials in large quantities in a reproducible way under conditions compatible with current industrial technologies. This would speed up the integration of this new class of materials in real world products.