Universität zu Köln

German, Raphael (2022). Raman Spectroscopy on Selected Cooperative Systems. PhD thesis, Universität zu Köln.

PDF (PhD Thesis) PhD_Raphael_German.pdf - Accepted Version Download (12MB)

Abstract

In this work we present di erent classes of materials, mainly investigated by Raman spectroscopy. It will be shown that even local symmetry changes in uences the macroscopic properties of a material, and that Raman spectroscopy is a versatile tool, also in combination with other experimental and theoretical techniques, to investigate complex materials. Optical microscopy, micro-photoelectron spectroscopy and micro-Raman spectroscopy showed in Y0.63Ca0.37TiO4 that the temperature-driven conducting properties arise by the percolation of local conducting phases, forced by local structural changes. Simultaneously measured resistivity and macro-Raman spectroscopy on Ca2Ru0.99Ti0.01O4 , along with phonon mode calculations, demonstrated the impact on the metal-insulator transition and the magnetic ordering by an applied electric current. Polarizationdependent Raman scattering and density functional studies point to the conclusion in BiSbTeSe2 that the preferred local structure breaks inversion symmetry and explains consequently the unexpectedly high number of Raman active phonon modes. Timeresolved spontaneous Raman scattering spectroscopy on surface aligned 7-atom wide armchair graphene nanoribbons revealed that the exciton dynamics can be traced by optically induced changes of the phonon population.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language Raman Spektroskopie an ausgewählten kooperativen Systemen German
Creators:	Creators Email ORCID ORCID Put Code German, Raphael raphael.german@gmx.net UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-646456
Date:	11 July 2022
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language Raman Spectroscopy English Solid State Physics English Cooperative Systems English
Date of oral exam:	6 October 2022
Referee:	Name Academic Title van Loosdrecht, Paul H.M. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/64645