Ferroelectric and Dielectric Properties of Hf0.5Zr0.5O2 Thin Film Near Morphotropic Phase Boundary

Recently, based on the phase-field modeling, it is predicted that Hf1-xZrxO2 (HZO) exhibits the morphotropic phase boundary (MPB) in its compositional phase diagram. Herein, the effect of structural changes between tetragonal (t) and orthorhombic (o) phases on the ferroelectric (FE) and dielectric properties of HZO films is investigated to probe the existence of MPB region. The structural analysis shows that by adjusting the ozone dosage during the atomic layer deposition process and annealing conditions, different ratios of t- to o-phases (fto) are achieved, which consequently affect the FE and dielectric properties of the samples. Polarization versus electric field measurements show a remarkable increase in FE characteristics (P-r and E-c) of the sample that contains the minimum t-phase fraction (fto approximate to 0.04). This sample shows the lowest epsilon r compared with the other samples, which is due to the formation of FE o-phase. The sample that contains the maximum fto approximate to 0.41 demonstrates the highest dielectric response. By adjusting fto, a large epsilon r of approximate to 55 is achieved. The study reveals a direct relation between fto and epsilon r of HZO thin films, which can be understood by considering the density of MPB region.