Structural and Electronic Surface Dynamics
Max Planck Research Group
Fritz Haber Institute of the Max Planck Society
Department of Physical Chemistry
room: A 1.16
phone: +49 30 8413 5135
fax: +49 30 8413 5106
2006-2011: Physics Diploma, University of Patras, Greece.
2011-2013: Master of Materials Science, University of Patras, Greece (Supervisor Dr. S.N. Yannopoulos).
August-October 2011: Undergraduate Internship in FORTH/ICEHT.
March-May 2013: Erasmus Placement in Forschungszentrum Julich.
2012-2014: Research assistant in FORTH/ICEHT.
Previous scientific interests
1) Laser-assisted fabrication of low dimensional Chalcogen nanostructures: Laser irradiation of low-band gap and low melting point Chalcogens leads to intense evaporation. From the supersaturated mixture of vapors and air, crystallites are precipitated with a certain geometry that reflects the symmetry of the crystalline lattice. Those crystallites act as seeds for further condensation of vapors. If the crystalline lattice is highly anisotropic (as in the case of t-Te and t-Se) one dimensional nanostructures (tubes or rods) are created. The process is carried out in ambient atmosphere and without the use of any hazardous solvents like in wet-chemistry approaches.
Reference: Th. Vasileiadis, V. Dracopoulos, M. Kollia, and S. N. Yannopoulos, “Laser-Assisted Growth of t-Te Nanotubes and their Controlled Photo-induced Unzipping to ultrathin core-Te/sheath-TeO2 Nanowires“, Scientific Reports (Nature) 3, 1209 (2013).
2) Photo-induced structural changes of Chalcogens: Chalcogens and their compounds have high sensitivity to external stimuli such as heat or light. During irradiation with low light intensity and visible wavelengths photo-induced oxidation and amorphization of t-Te is observed. Absorption of Oxygen distorts the Te chains resulting in a new wide peak in the Raman spectrum that corresponds to a-Te. The exact mechanism of oxidation must involve segmentation of Te chains and creation of unsaturated edges with an unpaired electron since the energy of photons is not sufficient to excite O2 molecules and make them reactive. For short exposure times and low intensity a small amount of oxide is formed that is confined on the surface. Surface confinement affects the short range order of glassy TeO2 as it is observed by Raman spectrum.
Reference: Vasileiadis, Thomas and Yannopoulos, Spyros N., “Photo-induced amorphization and oxidation of trigonal Tellurium: A means to engineer hybrid nanostructures and explore glass structure under spatial confinement“, Journal of Applied Physics 116, 103510 (2014).