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Two-dimensional materials have a large fraction of their atoms, if not all of them, directly "feeling the world" around them. Their properties can thus be strongly influenced by the contact to other materials, for instance a growth substrate, and in return, materials with a large contact-to-volume ratio will be influenced by their interface with the two-dimensional material. Different kinds of interactions and sometimes unconventional properties are found depending on the nature of the two-dimensional material and of the contacted material. In the past few years, we have addressed single-layer graphene and molybdenum disulphide, which have very different electronic properties -- semimetallic and semiconducting respectively. We prepare these materials by epitaxial growth on metallic substrates, and in between the two materials, we intercalate very thin layers of transition or alkali metals. Our first concern is to understand (and hopefully, control) how the process of intercalation occurs, whenever possible with the help of real-time observations. Is it reversible? Is the space between the two-dimensional material and the substrate, where the intercalated material grows, sealed? And how confined growth can occur in such a sealed two-dimensional region? Our interest is then on the effects of the interaction between the two-dimensional material and the intercalated layer. We have discovered that the magnetic properties of cobalt intercalated underneath graphene are very unusual, with a strong tendency to perpendicular-to-the-surface magnetisation that is appealing for spintronics applications. Using cesium intercalation, we observe electron doping in molybdenum disulphide together with a significant electronic disorder.

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Johann Coraux, Institute Neel, Grenoble
Seminar Room of the Institute of Physics II
Contact: T. Michely