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Author:Kanerva, Pekka Tapani
Title:Application of the phase field crystal model to strained metallic overlayers
Faasikenttäkidemallin soveltaminen jännittyneisiin metallisiin päällyskerroksiin
Publication type:Licentiate thesis
Publication year:2013
Pages:57      Language:   eng
Department/School:Teknillisen fysiikan laitos
Main subject:Fysiikka (laskennallinen fysiikka)   (Tfy-105)
Supervisor:Ala-Nissilä, Tapio
Instructor:Ala-Nissilä, Tapio ; Merikoski, Juha
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201507013624
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  3731   | Archive
Keywords:phase-field crystal
amplitude expansion
heteroepitaxy
thin films
faasikenttämallinnus
amplitudikehitelmä
heteroepitaksiaaliset systeemit
ohutkalvot
Abstract (eng): Most metallic systems experience a phenomenon called surface reconstruction where the surface atoms on a crystal have a structure that is different from the bulk.
Surface reconstruction often arises in heteroepitaxial systems, where a crystalline adsorbate film is grown on a crystalline substrate of a different material.
In such systems, a mismatch is present between the lattice spacing of the adsorbate and that of the substrate.
Due to the mismatch, strain is generated at the interface between the materials, which often leads to spontaneous surface patterning.

In this thesis, an amplitude expansion methodology of the Phase-field crystal (PFC) model is used to model the structure of stable and metastable heteroepitaxial films on length scales of several hundred nanometres while being also able to resolve the atomistic resolution.
We were able to reproduce realistically the surface ordering that can be seen experimentally in many metallic heteroepitaxial overlayers and make predictions for systems where the experimental results are limited.
Abstract (fin): Useimmilla metalleilla voidaan havaita ilmiö, jossa pinnan atomit uudelleenjärjestäytyvät, eli kiteen pinta-atomien hilarakenne on erilainen kuin kiteen sisällä olevien atomien hilarakenne.
Tämä ilmiö on hyvin yleinen heteroepitaksiaalisissa (engl. heteroepitaxial) systeemeissä, joissa kiteinen, adsorboitunut ohutkalvo kasvaa eri materiaalista koostuvalle kiteiselle alustalle.
Tällaisissa systeemeissä adsorboituneen materiaalin hilavakio on erisuuruinen kuin alustan hilavakio.
Hilavakioiden välinen ero aiheuttaa jännitystä materiaalien väliselle rajapinnalle, mikä usein johtaa spontaaniin pintarakenteiden muodostumiseen.

Tässä tutkimuksessa käytetään faasikenttäkidemallin (engl.
Phase-field crystal, PFC) amplitudikehitelmämenetelmää (engl. amplitude expansion) stabiilien ja metastabiilien kalvojen rakenteen mallintamiseen.
Mallinnetut kalvot ovat jopa useiden satojen nanometrien kokoisia ja myös niiden atomirakenne voidaan selvittää.
Menetelmällä voitiin jäljentää realistisesti monissa metallisissa heteroepitaksiaalisissa systeemeissä kokeellisesti havaittuja pinnan järjestäytymisiä sekä tehdä ennustuksia systeemeille, joista kokeellisia havaintoja on niukasti.
ED:2013-04-03
INSSI record number: 46027
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