Crystallization of Amorphous Hf_1-xZr_xO₂ Thin Films by Electric Field Cycling

Hafnium oxide (HfO₂)-based ferroelectrics exhibit robust ferroelectricity even at extremely thin thicknesses, in contrast to conventional perovskite-based ferroelectrics. Numerous research efforts are underway to enhance the ferroelectric properties of HfO₂ and, recently, the crystallization of amorphous hafnium zirconium oxide (HZO) through electric field cycling has been reported. Electric-field-induced crystallization might enable the crystallization process to occur at lower temperatures compared to traditional methods. To investigate the mechanism of electric-field-induced crystallization, it is necessary to study nanoscale ferroelectricity analysis. However, the conventional approach of studying ferroelectricity using polarization-electric field hysteresis loop measurement is limited in its ability to discern the underlying nanoscale mechanisms due to the presence of leakage currents. In this study, we investigated the electric-field-induced crystallization of HZO thin film at the nanoscale level using piezoresponse force microscopy. This research can provide opportunities for understanding the electric-field-induced crystallization and origin of ferroelectricity of HfO₂-based thin films.<br/><br/><u>References</u><br/>[1] Lee, H. Choe, D.-H. Jo, S. Kim, J.-H. Lee, H. H. Shin, H.-J. Park, Y. Kang, S. Cho, Y. Park, S.Unveiling the Origin of Robust Ferroelectricity in Sub-2 Nm Hafnium Zirconium Oxide Films. ACS Appl. Mater. Interfaces 2021, 13, 36499–36506<br/>[2] S. Kang, W.-S. Jang, A. N. Morozovska, O. Kwon, Y. Jin, Y.-H. Kim, H. Bae, C. Wang, S.-H. Yang, A. Belianinov, S. Randolph, E. A. Eliseev, L. Collins, Y. Park, S. Jo, M.-H. Jung, K.-J. Go, H. W. Cho, S.-Y. Choi, J. H. Jang, S. Kim, H. Y. Jeong, J. Lee, O. S. Ovchinnikova, J. Heo, S. V. Kalinin, Y.-M. Kim, Y. Kim, Highly enhanced ferroelectricity in HfO₂-based ferroelectric thin film by light ion bombardment. Science 2022, 376, 731–738