Stabilization of phase-pure rhombohedral HfZrO4 in Pulsed Laser Deposited thin films

TL;DR

This paper demonstrates the epitaxial growth of phase-pure rhombohedral HfZrO4 thin films using Pulsed Laser Deposition, employing advanced microscopy and X-ray techniques to confirm their structure and polarity, which is crucial for electronic device applications.

Contribution

It introduces a method to grow and verify phase-pure rhombohedral HfZrO4 thin films with confirmed polarity using combined microscopy and diffraction techniques.

Findings

Epitaxial growth of phase-pure rhombohedral HfZrO4 on GaN/Si.

Use of DPC-STEM to image oxygen columns in the film.

Confirmation of polar rhombohedral R3 symmetry.

Abstract

Controlling the crystalline structure of Hafnium Zirconate and its epitaxial relationship to a semiconducting electrode has a high technological interest, as ferroelectric materials are key ingredients for emerging electronic devices. Using Pulsed Laser Deposition, a phase pure, ultra-thin film of HfZrO4 is grown epitaxially on a GaN (0001) / Si (111) template. Since standard microscopy techniques do not allow to determine with certitude the crystalline structure of the film due to the weak scattering of oxygen, differentiated differential phase contrast (DPC) Scanning Transmission Electron Microscopy is used to allow the direct imaging of oxygen columns in the film. Combined with X-Rays diffraction analysis, the polar nature and rhombohedral R3 symmetry of the film are demonstrated.