Etude théorique du transport électronique dans les empilements de matériaux 2D et les dispositifs associés

par Jean Choukroun

Projet de thèse en Electronique et Optoélectronique, Nano- et Microtechnologies

Sous la direction de Philippe Dollfus.

Thèses en préparation à Paris Saclay , dans le cadre de Electrical,Optical,Bio: PHYSICS_AND_ENGINEERING , en partenariat avec Centre de Nanosciences et de Nanotechnologies (laboratoire) , Nanoélectronique (equipe de recherche) et de Université Paris-Sud (établissement de préparation de la thèse) depuis le 01-10-2015 .


  • Résumé

    For about ten years the research on 2D materials and their applications has been limited to graphene and its nanostructres (nanoribbons, quantum dots, nanomeshes). However, the family of 2D layered materials has been recently extended to other metals, insulators and semiconductors like hexagonal-BN, silicene, phosphorene, and transition metal dichalcogenides (MoS2, MoSe2, WS2,…). It does not only enlarge the number of available layered materials but the ability to assemble them as in a lego-like game [Geim_2013] allows us also to form either in-plane heterostructures (as single sheets of graphene/BN hetero-domains) [Sutter_2012] or stacks of hetero-layers (connected by weak Van der Waals interactions) [Shi_2012, Yu_2013], which strongly broadens the possibilities of bandgap engineering and of tuning the electron and phonon transport properties, while still taking advantage of the exceptional transport properties of graphene. Additionally, as already demonstrated in bilayer graphene [Nguyen_2015], these properties may be very sensitive to the alignment of the hetero-layers, which makes the rotation of these layers an additional degree of freedom to control them. Efficient vertical transistors and thermoelectric devices have been already suggested and demonstrated [Britnell_2012, Nguyen_2014a]. However, this research area is still in its infancy and it opens a wide field of investigation with potentially high impact. The PhD thesis will consist in exploring different ways of 2D heterostructure design, from the simplest case of graphene/BN stacks were all materials are almost lattice-matched, to more complex structures including silicene or dichalcogenide mono-layers with graphene layers/contacts. Though the main objective will focus on the electron transport properties, extension to thermal transport and thermoelectric properties will be kept in mind. In each case, a multiscale approach will be developed, which will consist first in studying the basic material properties using first-principles calculation (for structures limited to about hundred atoms) and then switching to semi-empirical atomistic tight-binding simulation (with appropriate parametrization of hopping energies) in the non-equilibrium Green's function (NEGF) formalism self-consistently coupled with Poisson's equation. The latter approach is indeed suitable to the simulation of full devices of length typically greater than hundred nanometers [Berrada_2013, Nguyen_2014b]. This research will be led in collaboration with experimental groups working on this type of 2D materials. The main final objective of this work will be to propose new concepts of devices for nanoelectronics (diodes, transistors,…), able to operate under low power consumption. Optionally, thermoelectric devices will be investigated too.

  • Titre traduit

    Theoretical study of electronic transport in 2D material stacks and associated devices


  • Résumé

    For about ten years the research on 2D materials and their applications has been limited to graphene and its nanostructres (nanoribbons, quantum dots, nanomeshes). However, the family of 2D layered materials has been recently extended to other metals, insulators and semiconductors like hexagonal-BN, silicene, phosphorene, and transition metal dichalcogenides (MoS2, MoSe2, WS2,…). It does not only enlarge the number of available layered materials but the ability to assemble them as in a lego-like game [Geim_2013] allows us also to form either in-plane heterostructures (as single sheets of graphene/BN hetero-domains) [Sutter_2012] or stacks of hetero-layers (connected by weak Van der Waals interactions) [Shi_2012, Yu_2013], which strongly broadens the possibilities of bandgap engineering and of tuning the electron and phonon transport properties, while still taking advantage of the exceptional transport properties of graphene. Additionally, as already demonstrated in bilayer graphene [Nguyen_2015], these properties may be very sensitive to the alignment of the hetero-layers, which makes the rotation of these layers an additional degree of freedom to control them. Efficient vertical transistors and thermoelectric devices have been already suggested and demonstrated [Britnell_2012, Nguyen_2014a]. However, this research area is still in its infancy and it opens a wide field of investigation with potentially high impact. The PhD thesis will consist in exploring different ways of 2D heterostructure design, from the simplest case of graphene/BN stacks were all materials are almost lattice-matched, to more complex structures including silicene or dichalcogenide mono-layers with graphene layers/contacts. Though the main objective will focus on the electron transport properties, extension to thermal transport and thermoelectric properties will be kept in mind. In each case, a multiscale approach will be developed, which will consist first in studying the basic material properties using first-principles calculation (for structures limited to about hundred atoms) and then switching to semi-empirical atomistic tight-binding simulation (with appropriate parametrization of hopping energies) in the non-equilibrium Green's function (NEGF) formalism self-consistently coupled with Poisson's equation. The latter approach is indeed suitable to the simulation of full devices of length typically greater than hundred nanometers [Berrada_2013, Nguyen_2014b]. This research will be led in collaboration with experimental groups working on this type of 2D materials. The main final objective of this work will be to propose new concepts of devices for nanoelectronics (diodes, transistors,…), able to operate under low power consumption. Optionally, thermoelectric devices will be investigated too.