Driving ferroelectric domain walls towards greater roughness

Ferroelectric domain walls show thermally activated creep and progressively roughen when driven from the edges of planar electrodes, potentially limiting racetrack memory applications in thin films. This research is published in Applied Physics Letters.

Schematic representation of a ferroelectric device, in which domain walls behave as elastic lines pinned by disorder. © Dr. Nirvana Caballero – UNIGE

Domain walls are nanoscale boundaries separating regions with different orientation of polarisation in ferroelectric materials. They can present novel physical properties and have been the focus of intense research efforts for potential nanoelectronic applications, such as ferroelectric racetrack memories. To successfully integrate the domain walls into such devices, we need to understand and control their motion, stability, and shape in device-relevant geometries and operating conditions.

Using scanning probe microscopy, physicists in the group of Prof. Patrycja Paruch, UNIGE tracked the growth and roughening of these walls, driven by electric fields at the straight edges of planar electrodes deposited on thin films of the ferroelectric material  Pb(Zr0.2Ti0.8)O3 at both room temperature, and when heated to 100°C.  These measurements reveal that the motion of the domain walls is well described as thermally activated creep dynamics, governed by the competition between their elastic energy and the fluctuations of the disorder potential energy, established by material defects inherent in all such samples.  Importantly, they observe that initially flat domain walls launched from the electrode edges progressive roughen as they move further and further into the disorder landscape.  This roughening could prove a significant limiting factor for racetrack-type memories using ferroelectrics, and will significantly affect future device design.

Contact: Prof. Patrycja Paruch, +41 22 379 35 46

Read the article in Applied Physics Letter

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