STÉPHANE BERCIAUD ‘Optical Spectroscopy of Two-Dimensional Materials: From Suspended Graphene to van der Waals Heterostructures’
In the wake of graphene, a large family of layered materials has (re-)emerged as an outstanding playground to investigate the interplay between photons, electrons and phonons in the (quasi) two-dimensional (2D) limit. In particular, graphene, as a 2D semimetal with excellent electron transport properties and transition metal dichalcogenides (MX2, with M=Mo, W and X=S, Se, Te) as 2D semiconductors exhibiting strong light-matter interaction are promising candidates for realistic applications in electronic, opto-electronic and opto-electro-mechanical devices. In this seminar, we will focus on the fundamental properties of i) suspended graphene and ii) graphene-MX2 van der Waals heterostructures.
First, we will demonstrate how magneto-Raman spectroscopy can be employed to probe electronic excitations and many-body effects in pristine suspended graphene layers. We will then discuss our recent Raman-based study of deflection, strain and doping in opto-electro-mechanical devices made from suspended graphene.
In a second part, we will investigate near-field coupling in simple van der Waals heterostructures composed of a MX2 monolayer covered by a graphene monolayer. Using Raman and photoluminescence spectroscopies, we are able to quantify the efficiency of photoinduced electron transfer from MX2 to graphene and to address the competition between this process and other relaxation pathways, such as non-radiative energy transfer.
Work done with: G. Froehlicher (IPCMS), E. Lorchat (IPCMS), D. Metten (IPCMS), C. Faugeras (LNCMI), M. Potemski (LNCMI), D.M. Basko (LPMMC).
ICFO’s Seminar Room
Hosted by Prof. Adrian Bachtold