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Surface functionalization and characterization of 2D materials

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Thesis advisor : Pr Thierry ANGOT
Email and address : thierry.angot, Aix Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille, France
Tel : +334 91 28 28 02
Co-advisor : Dr Eric SALOMON, eric.salomon

Subject description :
The discovery of graphene, a material consisting in a single atomic layer of carbon, can be considered as a turning point in the development of two-dimensional (2D) materials and thus change the configuration of future device architectures. This breakthrough has opened up the possibility to isolate and explore the fascinating properties of several other materials that offer, to the status of a few atomic layers, new features as well as new applications [1, 2, 3, 4]. However, most of 2D materials can not be used in their pristine form as they do not necessarily present convenient electronic properties [5,6,7]. Therefore, a precise control of the electronic surface states of 2D materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization can be used to adjust the reactivity and electronic properties of 2D materials. This interdisciplinary project, situated at the interface between solid-state physics and supramolecular chemistry, is a largely unexplored field of research and present a great potential towards low-cost, flexible, efficient and scalable devices [8].
The topic of the proposed thesis is therefore to functionalize different 2D materials using atoms and organic molecules, characterized their physical properties and more specifically their electronic properties. More particularly we propose to work on the functionalization of two recent 2D materials : the silicene and germanene the counter part of graphene made of silicon and germanium respectively [2, 3]. We also intend to functionalize organic self-assembled monolayer either by co-adsorption of organic compound or by on-surface synthesis [9].
Growth and structural properties of the film will be characterized and determined combining low-energy electrons diffraction (LEED), scanning tunneling microscopy (STM) and Auger spectroscopy (AES). The reactivity, electronic and optoelectronic properties of the films will be probed using high-resolution electrons energy loss spectroscopy (HREELS) and photoelectron spectroscopy (PES).
The thesis will be carried out under ultra-high vacuum conditions, on an experimental station comprising :
- a sample preparation room equipped with a heating system, three calibrated evaporation sources, an atomic hydrogen source and an ion gun.
- two analysis chambers housing : a low-energy electron diffraction apparatus, a scanning tunneling microscope, an Auger spectrometer and a high-resolution electrons energy loss spectrometer.
Finally, to complete the measurements made in the laboratory and particularly for conducting the experiments by photoelectron spectroscopy, the student will also have to work on various synchrotron radiation facilities.
The candidate must have good knowledge in solid state physics and material sciences. In addition, he or she must be highly motivated by the experimental aspect of this thesis.
Bibliography :
[1] : M. Xu, et al., Chem. Rev., 113 (2013) 3766
[2] : P. Vogt, et al., Phys. Rev. Lett. 108 (2012) 155501
[3] : M. E. Dávila, et al., New Journal of Physics 16 (2014) 095002
[4] : L. Tao, et al., Nat. Nanotechnol. 10 (2015) 227
[5] : W. Wang et al., Phys. Rev. B 93 (2016) 081406(R)
[6] : D.B. Medina et al., J. Electron Spectrosc. Relat. Phenom., in press (2016)
[7] : C. Coletti et al., Phys. Rev. B 81 (2010) 235401
[8] : S. Lei et al., Nature Nanotech. 11 (2016) 465
[9] : N. Kalashnyk et al., Nat. Commun., in press (2017)