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Aurélien Lherbier

Study of electronic and transport properties of semiconducting nanowires and graphene planes

Published on 10 October 2008

Thesis presented October 10, 2008

This simulation and theoretical work is dedicated to the study of the electronic and mesoscopic transport properties of nanostructures. We use an efficient numerical method which allows us to compute the Kubo-Greenwood conductivity from a tight binding framework. This approach offers us the possibility to precisely study systems of several millions of atoms and thus to understand the transport mecanisms involved in low dimensionality disordered systems. After a brief description of the two nano-objects which we have been interessed in, the 1D silicon nanowires and the 2D graphene planes, and after a chapter describing the numerical methodology and the concepts related to the Kubo-Greenwood approach in real space, we study the impact of surface roughness on the electronic transport in silicon nanowires. We show that the transport performances of the material can be directly linked to the actual underlying electronic structure. We also show that as a function of their crystallographic orientation, great differences appear in the silicon nanowires electronic structure, which further condition the transport properties. Then we look at the case of doping the silicon nanowires and we discuss about the electronic screening effects. Finally, the last chapter is devoted to the impact of Anderson disorder and to the influence of dopants on transport in graphene planes. We notably show that the introduction of dopants can break the initial electron-hole symmetry which takes place in ideal graphene planes.

Nanowire, tight binding, electronic transport, semiconducting, localization, mobility, conductivity, surface roughness, doping

On-line thesis.