Sheeraz, Muhammad Ahn, Chang Won Duong, Nguyen Xuan Hwang, Soo­Yoon Jang, Ji­Soo Kim, Eun­Young Kim, Yoon Ki Lee, Jaeyeong Jin, Jong Sung Bae, Jong­Seong Lee, Myang Hwan Han, Hyoung­Su Kim, Gi­Yeop Cho, Shinuk Song, Tae Kwon Yang, Sang Mo Bu, Sang Don Baek, Seung­Hyub Choi, Si­Young Kim, Ill Won Kim, Tae Heon 2024-11-13T16:00:15Z 2024-11-13T16:00:15Z 2024-11-12 2024-12 https://pubs.kist.re.kr/handle/201004/151060 Understanding microscopic mechanisms of polarization retention characteristics in ferroelectric thin films is of great significance for exploring unusual physical phenomena inaccessible in the bulk counterparts and for realizing thin-film-based functional electronic devices. Perovskite (K,Na)NbO3 is an excellent class of lead-free ferroelectric oxides attracting tremendous interest thanks to its potential applications to nonvolatile memory and eco-friendly energy harvester/storage. Nonetheless, in-depth investigation of ferroelectric properties of (K,Na)NbO3 films and the following developments of nano-devices are limited due to challenging thin-film fabrication associated with nonstoichiometry by volatile K and Na atoms. Herein, ferroelectric (K,Na)NbO3 films of which the atomic-level geometrical structures strongly depend on thickness-dependent strain relaxation are epitaxially grown. Nanopillar crystal structures are identified in fully relaxed (K,Na)NbO3 films to the bulk states representing a continuous reduction of switchable polarization under air environments, that is, polarization retention failures. Protonation by water dissociation is responsible for the humidity-induced retention loss in nano-columnar (K,Na)NbO3 films. The protonation-driven polarization retention failure originates from domain wall pinning by the accumulation of mobile hydrogen ions at charged domain walls for effective screening of polarization-bound charges. Conceptually, the results will be utilized for rational design to advanced energy materials such as photo-catalysts enabling ferroelectric tuning of water splitting. English Wiley-VCH Verlag Protonation-Driven Polarization Retention Failure in Nano-Columnar Lead-Free Ferroelectric Thin Films Article 10.1002/advs.202408784 1 Advanced Science, v.11, no.48 Advanced Science 11 48 Y scie scopus 001358427200001 Chemistry, Multidisciplinary Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article ferroelectric (K,Na)NbO3 thin film polarization retention loss epitaxy