Atomistic simulations of electronic structure and coherent transport in 1D & 2D carbon-based nanoarchitectures

PhD Program

Speaker

Xabier Diaz de Cerio
DIPC

When

2025/02/28
10:30

Place

Hemiciclo of the Faculty of Psichology (UPV/EHU), Donostia / San Sebastián

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PhD Thesis defense by Xabier Diaz de Cerio

Supervisors: Arantzazu Garcia Lekue (DIPC, Ikerbasque)

Condendes Matter Physics - Theory and simulation of electronic processes in carbon-based nanomaterials

The miniaturization of silicon-based field effect transistors over the last 60 years has led to remarkable improvements in the performance of electronic devices. However, these basic electronic components have already reached sizes of a few nanometers, where their characteristics start to be affected by quantum mechanical phenomena. One-atom-thick materials, and specially those based in graphene, emerge as promising alternatives to silicon. In particular, it has been predicted that atomically precise nanometer-size pores can introduce important modifications in the electronic properties of graphene, for example opening a gap in the band structure or introducing quantum interference effects in the electron transport.

In this thesis, we theoretically study the electronic properties of porous 1D and 2D carbon-based nanoarchitectures fabricated with atomic precision using the on-surface synthesis technique. We employ density functional theory and tight-binding models in combination with non-equilibrium Green's functions to simulate the electronic structure and coherent quantum electron transport in different size scales, ranging from the atomic to realistic device levels. We shed light on a new synthetic route to fabricate porous graphene nanoribbons (GNRs) and we investigate how those nanopores affect the electronic structure of the system. Besides, we explore new strategies to tune the electronic anisotropy and quantum electron transport in nanoporous graphene (NPG), a lateral array of coupled GNRs. We show that engineering the molecular bridges connecting adjacent GNRs can be used to enhance the electronic anistropy and control the electronic Talbot interference effect, a phase coherent phenomena governing large-scale electron transport in NPG. Apart from intrinsic modifications of the atomic structure, we explore the stacking of NPG on graphene. We analyze the dependence of the electronic properties and the Talbot effect on the twist angle between the layers and provide fingerprints for the experimental verification of our predictions. Finally, we address the origin of the deceptive electronic density confinement in spectroscopic measurements performed with scanning tunneling microscopy on GNRs and NPG. All in all, the simulations reported in this thesis provide support for the understanding and analysis of experimental measurements. Moreover, our predictions open new pathways towards the design of electronic devices based on the nanoscale control of electronic currents and phase-coherent transport phenomena in carbon-based nanoarchitectures.