Ferroelectric Switching Pathways and Energetics in (Hf,Zr)O2

• Published in: ECS transactions 2017-01, Vol.75 (32), p.107-121
• Main Authors: Barabash, Sergey V., Pramanik, Dipankar, Zhai, Yahong, Magyari-Kope, Blanka, Nishi, Yoshio
• Format: Article
• Language: eng ; jpn
• ISSN: 1938-5862; 1938-6737
• DOI: 10.1149/07532.0107ecst

From first principles, we investigate the ferroelectric behavior of (Hf,Zr)O2 and the ways to control the observed polarization. The previously reported energetic phase hierarchy is confirmed and refined using the more accurate hybrid functionals. Possible ferroelectric switching pathways are systematically studied. The pathways corresponding to the highest hypothetically attainable polarization are energetically unfavorable. The lowest activation energy is found for a family of nearly-degenerate pathways, leading to different final ferroelectric configurations yet all involving a tetragonal-like local minimum midway between two transition states. These pathways correspond to a single-domain observed "remnant polarization" of either 0.55C/m2 (0.51C/m2) in ZrO2 (HfO2), or only 0.39 C/m2 (0.36 C/m2 respectively). Domain wall energetics may play a key role in determining which pathways would actually be observed, highlighting the importance of the domain structure. Preliminary evidence is presented that strain can be used as means of manipulating switching pathways and the resulting electrical characteristics.