Interacting si nanocrystals in a-SiO2 : a Monte Carlo study

Εμβυθισμένοι νανοκρύσταλλοι si σε a-SiO2 : μαι μελέτη Monte Carlo

Κλεοβούλου, Κωνσταντίνος

Κελίρης, Παντελής

Silicon nanocrystals (Si-nc) embedded in amorphous dielectric matrices (a-SiO2) have attracted considerable attention both for their fundamental properties and potential applications in Si-based optoelectronic and quantum computing devices. It is particularly a very interesting subject to realize ordered Si-nc assemblies (quantum dot photonic crystals or two-dimensional superlattices). For such an aim, it is necessary to control both the size of Si-nc and their inter-particle distances and positioning/ordering. Despite its importance, a lot of issues concerning the interparticle interaction of Si-nc still remain unclear. We present here results of Monte Carlo simulations which shed light onto these issues. In our approach, the generation of the embedding a-SiO2 structure is achieved via a modified Wooten-Winer-Weaire method. Starting from crystalline betacristobalite, the network is amorphized through bond-breaking and switching moves. The Si-nc is positioned at the center of the cell. The energies are calculated using the Keating-like potential. Bond-conversion moves of the type Si-Si to Si-O-Si, and vice versa, allows us to study interdiffusion in the system. A 3.0 nm Si-nc is chosen for our simulations. Through the periodic boundary conditions the inter-particle distance of the nc vary from 0.5 to 4.0 nm. The energetics, stability and mechanical properties of embedded Si-nc in a-SiO2 and their variations versus the inter-particle distances are examined. We have shown that the interface properties of Si-nc are strongly influenced by the embedding amorphous oxide matrix. We especially find that the interfacial energy decreases with the variation of the interparticle distance, indicating higher stability of the entire nanocomposite system. There is also indication for preferential ordered arrangements of Si nanocrystals at optimum distances. Large deformations were observed, with the deviations in bond angles to be the dominant contributor to the strain energy. Our findings might play a crucial role in understanding and optimizing the PL properties of ordered Si-nc assemblies. (EN)

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Τύπος Εργασίας--Μεταπτυχιακές εργασίες ειδίκευσης

Εμπειρικό δυναμικό

Empirical potential

Metropolis algorithm

Μέθοδος των www

www method

Πανεπιστήμιο Κρήτης

E-Locus Ιδρυματικό Καταθετήριο

Elocus

Αγγλική γλώσσα

2009-11-20

http://elocus.lib.uoc.gr:443/dlib/2/e/4/metadata-dlib-e3f27c073e3e17d5936b56f8ff22c5ef_1258706503.tkl

000351179

Σχολή/Τμήμα--Σχολή Θετικών και Τεχνολογικών Επιστημών--Τμήμα Φυσικής--Μεταπτυχιακές εργασίες ειδίκευσης