Thickness scaling and ferroelectric switching in wurtzite structure zinc magnesium oxide thin films

Abstract

This study reports the thickness scaling of sputtered ferroelectric Zn0.61Mg0.39O (ZMO) thin films down to 43 nm. Encapsulated IrO2/ZMO/Ir capacitors exhibited switchable polarizations exceeding 50 μC cm−2 and coercive fields that increased from 3.9 to 4.4 MV cm−1 as the thickness decreased. Switching kinetics are best described by the simultaneous non-linear nucleation and the growth model. Bimodal switching is prevalent at low thicknesses, with the fastest switching times measured to be approximately 400 ns. Device encapsulation made ZMO switching kinetics more abrupt, potentially due to changes in the concentration of atmosphere-induced defects such as hydroxides. These results demonstrate stable ferroelectricity and sub-microsecond switching in sub-50 nm wurtzite ZMO, highlighting its potential as a low-voltage ferroelectric for integrated nonvolatile memory applications.