USIAS Fellows seminar: Playing atomically thin drums
By Stéphane Berciaud (2015 Fellow)
Over the past fifteen years, intense research activity has emerged on the science of so-called two-dimensional (2D) materials. These systems compose a unique toolkit of one or several atom-thick building blocks. In their planes, 2D materials are held together by strong chemical bonds, but stack out of their planes due to much weaker electrostatic interactions, known as van der Waals forces. Graphene (made from the well-known material graphite), boron nitride (BN) and transition metal dichalcogenides (for instance molybdenum disulfide, MoS2) are currently the most popular members of the 2D materials family.
Two-dimensional materials are endowed with remarkable electronic properties and interact strongly with light, for instance with a laser beam. Such assets are suitable for efficient opto-electronic devices (e.g., photodetectors, solar cells). At the same time, 2D materials are lightweight and sensitive nanomechanical systems that can be finely controlled electrically and optically, as illustrated in figure 1.
In this seminar, Stéphane Berciaud will introduce the basic features of 2DM, with a strong focus on graphene. He will then explain how one can fabricate the thinnest possible drum-skins (made from one atom thick graphene membranes!). Finally, he will survey the main results of the USIAS research project, which explored the interplays between the macroscopic vibrations of graphene membranes and their intrinsic, microscopic electronic and vibrational degrees of freedom. The latter are probed using an optical technique called Raman scattering spectroscopy, that will also be introduced.
This work was supported by the USIAS grant GOLEM (2015) and performed in collaboration with X. Zhang, K. Makles, D. Metten, H. Majjad and P. Verlot (USIAS co-fellow).
Legend: (left) Crystal structure of selected 2D materials, namely graphene (Gr), boron nitride (BN) and transition metal dichalcogenides (TMD). (Middle) Schematic of an opto-electro-mechanical system made from a suspended 2D membrane. (Right) Frequency-dependent displacement of an electrostatically actuated monolayer graphene drum (Data: Xin Zhang et al, IPCMS).
