  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.
