Aachen Graphene & 2D Materials Center
From material science to new device applications
The exceptional electronic properties of graphene make it a material with large potential for low-power, high-frequency electronics. However, the performance of a graphene-based device depends not only on the properties of the graphene itself, but also on the quality of its metal contacts. The lack of effective and manufacturable approaches to establish good ohmic contacts to a graphene sheet is one of the factors that limit today the full application potential of graphene technology.
One of the great assets of two-dimensional (2D) materials is the possibility of placing different materials on top of each other to form heterostructures with properties tailored to specific application scenarios. However, the quality of the final material stack strongly depends on the electronic coupling between the different materials. Measuring this coupling in a non-destructive way is therefore an important aspect for material development. Researchers from AMO GmbH, RWTH Aachen University and AIXTRON SE have now established a methodology based on Raman spectroscopy for estimating quantitatively the coupling between graphene and molybdenum disulfide (MoS2) in heterostructures up to the mm2-scale.
One of the big selling points of two-dimensional (2D) materials is their self-passivated nature, which allows them to be deposited on any substrate and opens up new possibilities for three-dimensional material stacks. The downside is their weak adhesion to the substrate, which can be a source of device instability. Quantifying the adhesion of 2D materials to three-dimensional surfaces is therefore an essential step for the reliable integration of devices based on 2D materials. A team of researchers around Max Lemme has now shown that the adhesion between 2D materials and substrates can be efficiently quantified using button-shear testing.
Researchers at the Aachen Graphene & 2D Materials Center have released an open-source platform to automatically identify and classify exfoliated flakes of two-dimensional (2D) materials on a substrate, shortening one of the most time-consuming and tedious tasks in the study of 2D materials.
In a recent study published in Nature Communications, researchers from RWTH Aachen University and Forschungszentrum Jülich have reported the observation of coherent charge oscillations in bilayer graphene quantum dots. This marks a significant milestone on the way to spin and valley qubits in a two-dimensional material system.
Good news for the community working on two-dimensional materials in Europe: a team of researchers at RWTH Aachen University has successfully implemented the process for growing high-quality hexagonal Boron Nitride at atmospheric pressure and high temperature, increasing the resilience of the supply chain of this unique material.
Scientists from RWTH Aachen, AMO GmbH, Forschungszentrum Julich and the University of Regensburg have shown that in twisted heterobilayers of WSe2 and MoSe2 there is a transfer of valley polarization from excitons in WSe2 to free carriers in MoSe2. This mechanism, which is strongly dependent on the twist angle, may allow the realization of opto-valleytronic devices where the valley polarization is optically excited but extracted and measured by electrical means. The results are reported in npj 2D Materials and Applications.
Researchers at RWTH Aachen University and Forschungszentrum Jülich have uncovered important characteristics of double quantum dots in bilayer graphene, an increasingly promising material for possible applications in quantum technologies. The team has demonstrated near-perfect particle-hole symmetry in graphene quantum dots, which could lead to more efficient quantum information processing. The study has been published in Nature.
Nowadays it is possible to grow high-quality graphene on large scale using chemical vapor deposition (CVD). What remains a major bottleneck for the industrialization of the material is the transfer of graphene from the growth substrate to a target one. A team of researchers from the University of Cambridge and RWTH Aachen University has now developed a methodology for optimizing simultaneously the growth and the transfer process, showing that it is possible to dry-transfer graphene with high-yield, if the crystallographic orientation of the growth surface is chosen appropriately.
Using advanced spectroscopic techniques, researchers from RWTH Aachen University have been able to observe for the first-time domains of tetralayer graphene with ABCB stacking. The results have been reported in ACS Nano.
