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Identifier

000404331

Title

Single-electron quantum states in gold nanostructures

Alternative Title

Μελέτη κβαντικών καταστάσεων ενός ηλεκτρονίου σε νανοδομές

Author

Ραπτάκης, Αντώνιος

Thesis advisor

Ρεμεδιάκης, Ιωάννης

Reviewer

Kοπιδάκης, Γεώργιος
Παπάζογλου, Δημήτριος

Abstract

In this master thesis, we studied surface-localized electronic states of metals. In particular, we determine characteristic properties of Schockley surface states[11,12,13,14,15] for Au and Cu slabs. We did the calculation using Density Functional Theory (DFT)[9,10]. We construct slabs with different number of atomic layers. These layers are parallel to the (100) and (111) plane of FCC structure. We solved the Ν-electron Schrödinger equation[8] as implemented in the open-source package Grid-based Projector Augmented Wave method (GPAW) [9,10,18]. We locate surface states by observing Bloch States, ( n⃗k ), where the probability of finding electrons at surface atoms is much higher than the probability of finding them in bulk atoms. We modify slab thickness (number of layers) and observe when the probability starts to converge. We confirm the surface states by applying three methods. In the first method, we find the diagram of the probability density per atom. The next method was a graphical way to prove the surface state, in which we examine wavefunction plots. For this method, we used VMD and ASE[17]. In the last method, we plot the probability density in real space. All three methods are used to confirm that a particular Bloch state is indeed a surface state. Subsequently, we repeated the same process for relaxed surfaces, in which the first and the last atom of slabs are allowed to relax. The next step of the thesis concerns the computational calculation of the workfunction for different thicknesses of slabs. We fitted the square of the absolute value of wavefunction and applying Schockley's Surface State theory, we found values for the metal's workfunction in very good agreement to direct simulation. Finally, we repeated the same process for Cu slabs. So far, Schockley's theory was applied and explained results in semiconductors. In this thesis,it is confirmed that this theory could be applied also to metalic surfaces, because it derived from nearly free electrons model.

Language

English

Subject

Surface states

Επιφανειακές καταστάσεις

Μοντέλο Schockley

Issue date

2016-11-18

Collection

School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Post-graduate theses

Type of Work--Post-graduate theses

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