SKM 2023 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 6: Thin Film Properties II (joint session DS/KFM)
DS 6.2: Vortrag
Dienstag, 28. März 2023, 10:15–10:30, SCH A 315
Dynamics of phase transition in Lead-free Ferroelectric thin films — •Mallika Khosla1, Jutta Schwarzkopf1, Daniel Schmidt2, Daniel Hensel1, and Peter Gaal1,2 — 1Leibniz-Institut für Kristallzüchtung, Berlin,Germany — 2Tailored x-ray products, Hamburg,Germany
In this contribution, we monitor the dynamics of the phase transition in Potassium Sodium Niobate (KNaxNb1-xO3) by taking snapshots of the structure after optical excitation using pulsed synchrotron radiation in a pump-probe scheme. Our sample is a 50 nm KNaxNb1-x O3 film grown on 20 nm thin SrRuO3 on TbScO3 substrate. The low-temperature phase displays a hierarchical order of domains and superdomains on sub-100 nm and on few um length scales, respectively. First, we show that laser heating with 7 ns pulses has a similar effect locally in terms of structural rearrangement as static heating of the whole sample volume. However, in our localized excitation the transient phase transition required to transform a similar volume fraction of the sample in the high temperature phase is about 5 times higher compared to static heating. Comparison with finite-element simulations of heat-transport in our sample shows that the phase transition dynamics does not exactly follow the temperature evolution in the ferroelectric film. In addition, time-resolved diffraction imaging experiments reveal that the stability of a spatial domain morphology has a nonlinear dependence on the local laser-induced temperature. Our results indicate that it is essential to resolve both the temporal and spatial coordinate to monitor the equilibration path of such phase transition.