Activation field-driven domain wall dynamics of nanobits in ferroelectric Al_0.7Sc_0.3N thin films

Non-oxide ferroelectric thin films, such as Al_1-xSc_xN (AlScN) thin films, have garnered significant interest for non-volatile memory applications due to their high remanent polarization. However, their large coercive electric fields present challenges for practical implementation. In this study, the domain switching dynamics of epitaxial AlScN thin films with thicknesses of 50, 100, and 150 nm were systematically investigated using piezoresponse force microscopy. The AlScN thin films, deposited on (111)-oriented Pt/MgO substrates, exhibited c-oriented epitaxial growth with a wurtzite structure. The remanent polarization improved with decreasing film thickness, attributed to the increase in the out-of-plane lattice constant. During the formation of ferroelectric polarization nanobits, domain wall migration speeds increased significantly with higher applied voltages. Furthermore, activation fields for domain wall motion, determined using Merz's law, decreased with increasing film thickness, reaching 14.3, 13.2, and 12.2 MV/cm for thicknesses of 50, 100, and 150 nm, respectively. By achieving an information density of approximately 2.1 T/in², these findings provide critical insights into the tunable ferroelectric properties of AlScN thin films, paving the way for their integration into ultrahigh-density data storage and next-generation non-volatile memory devices.