Phase field crystal modeling of graphene/hexagonal boron nitride interfaces
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Journal Title
Journal ISSN
Volume Title
Perustieteiden korkeakoulu |
Master's thesis
Authors
Date
2019-06-18
Department
Major/Subject
Physics of advanced materials
Mcode
SCI3057
Degree programme
Master’s Programme in Engineering Physics
Language
en
Pages
140+8
Series
Abstract
Two-dimensional materials such as graphene and hexagonal boron nitride(h-BN) are an important class of materials that have enhanced structural and electronic properties in comparison to their bulk counterparts. However, the limited length and time scales of the traditional modeling methods, such as the molecular dynamics (MD) and the quantum mechanical density functional theory (QMDFT) methods poses a severe challenge to study the underlying mechanism of various properties of these materials and their heterostructures. The phase field crystal (PFC) model can reach diffusive time scales (relevant e.g. in nucleation and growth of crystallites, relaxation of strain-driven 2D monolayers, and thermal conduction) that are much larger in comparison to MD and QMDFT methods while retaining atomic resolution. The model also incorporates an atomic length scale and elastic and plastic deformations in a natural manner. Various PFC models have been used to study topological defects, such as pentagon-heptagon (5|7) defects and inversion grain boundaries formed in the graphene and h-BN monolayers, respectively. In this work, we generalize the one-mode PFC model to study graphene/h-BN interface heterostructure by using the conserved dynamics to describe the dynamics of the model. The model was used to determine the elastic constants of the graphene and h-BN monolayers by uniaxial and biaxial stretching of the respective single crystals. The model highlighted the formation of topological defects such as pentagon-heptagon (5|7) defects at the interface of the in-plane graphene/h-BN heterostructure. Lastly we used the model to find the equilibrium shape of crystal of the h-BN crystal embedded in a graphene monolayer.Description
Supervisor
Ala-Nissila, TapioThesis advisor
Hirvonen, PetriKeywords
graphene-hexagonal boron nitride interfaces, phase field crystal model, conserved dynamics, mechanical properties, equilibrium shape of crystal, chemical potential fields