Science and Technology of Graphene
A little more than a decade ago, graphene has moved into the focus of scientists. Graphene “is a single carbon layer of graphite structure, describing its nature by analogy to a polycyclic aromatic hydrocarbon of quasi infinite size”.1 Graphene has been known before (even though it was sometimes called differently). For example, the electronic structure of graphene was already calculated in 1947 by Wallace2 using a tight binding approach. Interestingly, its calculated electronic and vibrational properties were frequently employed to explain electronic and vibrational properties of carbon nanotubes (see e.g. Refs. 3 and 4). The increase in truly graphene-focused activities, however, was triggered by reports on high carrier mobility and unconventional magneto-transport properties.5-8 The fascinating properties of graphene – some of which are record setting – have since then been investigated by many groups.
As a result of the increased interest in the field of graphene a round table meeting funded by the German Research Council (Deutsche Forschungsgemeinschaft, DFG) was held in September 2008 at Kloster Banz (Germany) with 30 participants from institutions all over Germany. The program included 22 presentations covering various aspects of graphene research including theoretical and experimental work on graphene properties, transport, growth and devices, giving an overview of activities in Germany. Following this meeting, a proposal for a DFG Priority Programme was developed and submitted in fall 2008. The DFG granted the Priority Programme 1459 Graphene in spring 2009 and the first funding period with 38 scientific projects and one coordination project commenced in fall 2010. In the second funding period 40 scientific projects and one coordination project were funded. The projects covered many subtopics of graphene science, including theoretical and experimental studies of basic physical properties of graphene, electronic transport and magneto-transport, graphene synthesis and growth of graphene and graphene nanoribbons on various substrates, the chemistry of graphene, and graphene device physics.
The present special issue of Annalen der Physik with the title “Science and Technology of Graphene” includes 14 Feature Articles, 3 Review Articles and 6 Original Papers, summarizing and reporting research performed within the Priority Programme 1459 Graphene. Five contributions review and report on various aspects of graphene growth by chemical vapor deposition on metal substrates, sublimation growth on silicon carbide, or by using aromatic self-assembled monolayers as a precursor. Both, extended graphene layers and graphene ribbons are considered, and interface manipulation by intercalation is discussed. Six papers are focused on charge carrier transport and magneto-transport in graphene, bilayer graphene and related carbon materials taking into account effects of dimensionality, twist angles in bilayer graphene, defects such as monolayer/bilayer transitions or stacking faults. In two contributions, scanning tunneling microscopy and spectroscopy are used to study the electronic states of graphene quantum dots as well as of ultra-thin metallic layers on graphene. The technological aspects of the integration of graphene into devices and the physics of graphene devices is the topic of four papers. In particular, field effect devices with extended graphene sheets as well as with graphene nanoribbons are discussed. Two papers are focused on theoretical and experimental investigations of the charge carrier dynamics in graphene. The interaction of light with graphene is the topic of another two contributions. While one deals with the interaction of THz radiation with graphene, the other one is focused on inelastic scattering processes (Raman scattering) in graphene nanoribbons. In one paper, self-energy effects on the magnetic ordering transition in monolayer and bilayer graphene are studied theoretically. Finally, one paper reviews synthesis and applications of novel 1D and 2D graphdiynes.
The interest in graphene is still very high as indicated by the still growing number of publications and requested funding. On the other hand, being a relatively young material, graphene still has to overcome several issues such as, for example, cheap large scale production in quantities and qualities depending on the application, process compatibility, etc. Furthermore, it has to compete with other, often more mature materials and technologies. Through more than 350 publications, the research performed within the SPP 1459 had a considerable impact on the current understanding of the science and technology of graphene, hence contributing to the foundation on which future applications can be developed.
Graphene, the single carbon layer of graphite structure (see above), is also the first truly two-dimensional material that has been investigated in depth. However, there are numerous materials that – like graphene – exist in the form of covalently bound layers stacked on-top of each other by van-der-Waals interaction.9-12 Monolayers of various representatives of this group have been prepared which frequently show different properties as compared to 3D bulk crystals. As an example the direct bandgap of monolayer MoS2 shall be mentioned which gives rise to a high photoluminescence yield.13 There is an ongoing development of various two-dimensional materials with different electronic properties (metallic, insulating, semiconducting, or even superconducting) and increased research activity in the field of 2D materials with the ultimate goal to integrate them, for example in the form of 2D heterostructures, into electronic devices. On the way to that goal, new and interesting scientific and technological results can be expected.
I would like to thank several persons who have had a great impact on the SPP 1459. First, I would like to acknowledge Dr. Michael Mößle from the DFG and his team for excellent and continuous support before and during the two funding periods. Furthermore, I would like to thank all the colleagues who contributed to the initial proposal for the SPP, especially U. Starke, J. Wintterlin, R. Haug, J. Smet, B. Trauzettel, H. Kurz and D. Neumaier. Last but not least, I would like to thank my co-coordinators Björn Trauzettel and Heinrich Kurz. Sadly, Heinrich Kurz passed away unexpectedly on the 12th of March, 2016. His passion for the topic was essential input for the SPP 1459.
Chemnitz, 16th of August, 2017
Thomas Seyller
Acknowledgements
Funding of the SPP 1459 was provided by the DFG. The coordination of the SPP 1459 was supported by the DFG through the projects SE 1087/11-1 and SE 1087/11-2.
