Public defence in Engineering Physics, M.Sc. Seyed Arsalan Hashemi Petrudi

Title of the doctoral thesis: Modeling Raman and Photoluminescence Spectra of Defective Materials

Opponent: Professor Pekka Koskinen, University of Jyväskylä, Finland
Custos: Professor Tapio Ala-Nissilä, Aalto University School of Science, Department of Applied Physics

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

Electronic thesis

Public defence announcement:

The doctoral thesis "Modeling Raman and Photoluminescence Spectra of Defective Materials" focuses on simulating Raman and photoluminescence spectra to investigate defects signatures in materials. An efficient computational method to simulate Raman spectra of large systems, which applies to alloys and systems with a small number of defects is devised. The method is based on the projection of vibrational eigenvectors of the supercell to the eigenvectors from the pristine primitive unit cell and using the Raman tensors calculated for the latter. Using photoluminescence and accounting for electron-phonon interactions, we investigate vibronic structures of color centers and calculate phonon side bands. Through this thesis, the behavior of phonons in several two-dimensional semiconducting alloys is explored. We demonstrate that (i) the so-called mass approximation significantly facilitates the calculation of Raman spectra, (ii) simulating the Raman spectra for defective materials can be done by a combination of empirical potentials and quantum mechanical density functional theory calculations, (iii) the so-called phonon confinement model can be used to capture the asymmetric broadening of the prominent peaks. In the context of photoluminescence, we compare the vibronic structures of different color centers by evaluating several important characteristics that are experimentally achievable.

Contact details of the doctoral student: [email protected], 0468464230

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