Konrad Wilczyński
supervisor: Mariusz Zdrojek
The purpose of this work is the study of temperature dependence of lattice vibration energies in layered materials, including two-dimensional films and heterestructures. The analysis is being performed with the use of ab-initio and molecular dynamics computational methods. The understanding of the phonon properties is necessary to properly interpret experimental results of Raman spectroscopy, which is one of the preferrable methods for material characterization.
Ab-initio simulations enable to study quantum-mechanical properties of lattice vibrations (i.e. their energy levels) and identify physical phenomenons responsible for the observed experimental results (such as phonon-phonon interactions, thermal expansion, lattice defects). Molecular dynamics computation, on the other hand, as performed at different lattice temperatures, helps to identify creation of lattice defects and enables to validate the results obtained with quantum-mechanical methods.
The material being studied in the thesis at the moment is titanium disulphide (TiS2). Its potential, promising applications include: thermoelectric devices, biosensors, energy storage and solar cells. However, phonon properties of titanium disulphide are still poorly understood: the origin of one of the experimentally observed Raman peaks is unknown and its temperature dependence is intriguing. The understanding of this phenomenon can be useful for further characterization of TiS2 films for advanced applications.