Defence of doctoral thesis in the field of applied physics, M.Sc. Natalia Berseneva

Title of the doctoral thesis is "Structure and properties of two-dimensional BCN materials from first-principles calculations"

Modern electronics demands durable materials with not only desired electronic properties, but also with specific magnetic characteristics. One way to satisfy this demand is to develop new composite systems with tuneable characteristics. Such systems can be created e.g. from two different materials that are structurally similar but have contrasting electronic properties. In particular, hexagonal boron nitride (h-BN) and graphene (consists of C atoms) are suitable candidates for this purpose.

The research presented in this thesis is focused on studying different properties of two-dimensional BCN alloys consisting of B, N, and C atoms. Different arrangements of atoms are considered – e.g., when either B, N, and C are randomly distributed across the structure, or C atoms are substituting B and N atoms in h-BN base structure.

The thesis reveals that the mechanical and electronic properties of 2D BCN structures are governed by concentrations and arrangements of the constituent elements. It is shown that the electron energy band gap of the BCN material can be continuously tuned from zero, as in graphene, to that of pristine h-BN (about 6 eV), what suggests the possibility to manufacture 2D semiconductor with a controllable band gap. The thesis illustrates that although h-BN is a non-magnetic material, it exhibits magnetic moments when B or N atoms are substituted by C. In addition, the thesis presents results on how the use of ruthenium substrate facilitates formation of a non-homogeneous BCN monolayer on top of it. The thesis also reports mechanical properties of mixed BCN systems and shows that due to their excellent mechanical properties, h-BN structures can be used as reinforcing agents in bulk materials. An example of reinforcing of bulk aluminium by h-BN sheets and nanotubes is described.

The results of this thesis can support progress in simulations and experimental work focused on 2D materials with defects.

Opponent is Professor Elena Besley, University of Nottingham, United Kingdom

Custos is Professor Patrick Rinke, Aalto University School of Science, Department of Applied Physics

Contact details of the doctoral student: [email protected]

The public defence will be organised via Zoom. Link to the event

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The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University

Electronic thesis

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