Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 22: Poster Monday: Surface Structure, Epitaxy, Growth and Tribology
O 22.1: Poster
Montag, 5. September 2022, 18:00–20:00, P4
Ordering processes and phase transitions in amorphous carbon thin films induced by optical excitation — •Carl Arne Thomann1, Adrian Wittrock1, Alexandra Wittig2, Filipe Lopes Dias2, Dominic Stangier2, Wolfgang Tillmann2, and Jörg Debus1 — 1Experimentelle Physik 2, TU Dortmund — 2Lehrstuhl für Werkstofftechnologie, TU Dortmund
Amorphous carbon is a metastable network of short-range ordered carbon atoms often used as protective coatings owing to their exceptional tribological properties. However, high temperatures in a tribological contact may cause considerable changes in the structural ordering, solid-to-solid phase transitions, and degradation of the film. In this work, we present an optical method to initiate and investigate the structural evolution including ordering processes of differently modified films. A pulsed pump laser with micrometer spot size introduces heat into the film, while a second laser probes the Raman scattering signatures. Increasing with laser power, five different stages of structural evolution are found: The first one is coined by thermally resistive amorphous carbon. It is followed by a continuous reduction in the number of lattice defects and non-sixfold aromatic rings. Further increasing pumping power induces a transition from a-C to defected graphite and eventually leads to graphite-dominant defect relaxation and an enhancement in hexagonal lattice areas. Our optical method provides a versatile tool to analyze temperature-induced structural surface changes in a controlled manner, which will improve the understanding about the conditions in tribological contacts.