# Interface Engineering Using Multiple La-Doped HfO2 Epitaxial Subnanolayers To Improve the Ferroelectric Properties of Hf0.5Zr0.5O2 Films

## TL;DR

This paper shows that adding lanthanum-doped hafnium oxide layers improves the stability and performance of ferroelectric hafnium-zirconium oxide films for device applications.

## Contribution

The study introduces a multilayer design with La-doped HfO2 subnanolayers to enhance ferroelectric stability and endurance in Hf0.5Zr0.5O2 films.

## Key findings

- Multilayer structures show no wake-up or fatigue up to 105 cycles.
- The coercive field is reduced by ≈25% with lower leakage due to a columnar microstructure.
- Dielectric permittivity and resistive switching up to 108% are observed.

## Abstract

The fabrication of ferroelectric multilayer systems based
on hafnia
represents a promising approach for achieving high-performance ferroelectric
devices. Electrical cycling instability is, in this regard, a key
barrier to commercialization. Here, we report on the incorporation
of La:HfO2 subnanolayers into an epitaxial Hf0.5Zr0.5O2 film, forming multilayer heterostructures.
Ferroelectric properties of multilayers are compared with single-layer
structures. We observe that wake-up and fatigue are not present up
to 105 cycles in the multilayers. The improved stability
is enabled by the ≈25% reduction of coercive field together
with the lower leakage resulting from the columnar microstructure
throughout the entire thickness without phase discontinuity at interfaces
and negligible presence of structural defects. This improvement on
endurance response is obtained while the polarization is maintained
in comparison with single Hf0.5Zr0.5O2 films; there is negligible loss of the polarization throught time
and there is a fast response time lower than 100 ns, limited by the
measurement circuit. In addition, dielectric permittivity and large
resistive switching up to 108%, not related to the ferroelectric
response, are also observed. These findings underscore multilayer
architecture as an interesting approach to improve properties while
also showing that careful selection of interlayer composition is critical
to improve device performance.