Optical spectroscopy of intrinsic graphene and graphene-based hybrid systems

Par Stéphane BERCIAUD, Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS

le mardi 16 Septembre à 14h, Salle des séminaires 3e étage bâtiment A4

Since 2004, graphene has risen as an outstanding system to investigate the interplay between photons, electrons and phonons in reduced dimensions. Furthermore, graphene is a promising candidate for realistic applications in electronic and optoelectronic nano-devices. In this seminar, we will focus on the optical response of monolayer graphene in the two limiting cases of i) a bare suspended sample and ii) a hybrid system composed of a single nano-emitter physisorbed on graphene.
First, we will show how the intrinsic properties of graphene can be probed using inelastic light (or Raman) scattering. This technique provides quantitative information about the electronic structure, the position of the Fermi level (i.e. the doping level), as well as the influence of disorder, strain, temperature, etc…. We will introduce two original studies based on Raman spectroscopy: i) an all-optical determination of the mechanical properties (Grüneisen parameters and Young’s modulus) of a pressurized graphene blister [1] and ii) the observation of (magneto-)Raman scattering by inter-Landau level electronic excitations in mono to penta-layer graphene [2].
The second part of this seminar will address the potential of graphene for the design of new hybrid materials and devices. In particular, we will discuss the interaction between graphene and colloidal semiconductor nanostructures, another promising class of nano-materials for photonics and photovoltaics. We performed a detailed study of resonant energy transfer (FRET) between individual CdSe-based (0-dimensional) nanocrystals and (two-dimensional) nanoplatelets deposited on (two-dimensional) graphene. Highly efficient energy transfer results in a shortening of the luminescence decay [3] and subsequent luminescence quenching. The energy transfer rate is further monitored as a function of the distance between the emitter the graphene layer. Our work demonstrates the realization of prototype graphene-based molecular rulers and uncovers the major influence of dimensionality on the FRET rate.
[1] An all-optical blister test on suspended graphene
D. Metten, F. Federspiel, M. Romeo, & S. Berciaud
arxiv :1407.1938
[2] Probing Electronic Excitations in Mono- to Pentalayer Graphene by Micro Magneto-Raman Spectroscopy
S. Berciaud, M. Potemski, & C. Faugeras
Nano Letters 14, 4548 (2014) doi : 10.1021/nl501578m
[3] Energy Transfer from Individual Semiconductor Nanocrystals to Graphene
Z. Chen, S. Berciaud, C. Nuckolls, T.F. Heinz, & L.E. Brus
ACS Nano 4, 2964 (2010) doi : 10.1021/nn1005107