Ferroelectric and dielectric properties of Hf0.5Zr0.5O2 thin film near morphotropic phase boundary

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