Stabilization of tetragonal/cubic phase in Fe doped Zirconia grown by atomic layer deposition

TL;DR

This study demonstrates that Fe doping in ZrO2 thin films grown by atomic layer deposition stabilizes the high-temperature tetragonal/cubic phases, which could enhance their magnetic properties for spintronic applications.

Contribution

It shows that Fe doping via ALD effectively stabilizes the tetragonal/cubic phases of ZrO2 at high temperatures, with controlled Fe content and chemical state.

Findings

Fe doping induces amorphization in ZrO2 films.

Fe stabilizes tetragonal/cubic phases after annealing.

Fe is present as Fe3+ in the films.

Abstract

Achieving high temperature ferromagnetism by doping transition metals thin films is seen as a viable approach to integrate spin-based elements in innovative spintronic devices. In this work we investigated the effect of Fe doping on structural properties of ZrO2 grown by atomic layer deposition (ALD) using Zr(TMHD)4 for Zr and Fe(TMHD)3 for Fe precursors and ozone as oxygen source. The temperature during the growth process was fixed at 350{\deg}C. The ALD process was tuned to obtain Fe doped ZrO2 films with uniform chemical composition, as seen by time of flight secondary ion mass spectrometry. The control of Fe content was effectively reached, by controlling the ALD precursor pulse ratio, as checked by X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry. From XPS, Fe was found in Fe3+ chemical state, which maximizes the magnetization per atom. We also found, by grazing incidence X-ray diffraction, that the inclusion of Fe impurities in ZrO2 induces amorphization in thin ZrO2 films, while stabilizes the high temperature crystalline tetragonal/cubic phase after rapid thermal annealing at 600{\deg}C.