A Robust Approach for the Growth of Epitaxial Spinel Ferrite Films

TL;DR

This paper presents a robust low-temperature method for growing high-quality epitaxial spinel ferrite films using pulsed laser deposition with ozone/oxygen, achieving atomically flat surfaces and enhanced magnetic properties.

Contribution

It introduces a novel 'vertical step-flow' growth mode and demonstrates epitaxial growth at lower temperatures than previously possible, independent of substrate type.

Findings

Epitaxial films achieved at temperatures below 550°C

Films exhibit atomically flat surfaces over large areas

Growth mode is independent of substrate and film thickness

Abstract

Heteroepitaxial spinel ferrites NiFe2O4 and CoFe2O4 films have been prepared by pulsed laser deposition (PLD) at various temperatures (175 - 690 {\deg}C) under ozone/oxygen pressure of 10 mTorr. Due to enhanced kinetic energy of ablated species at low pressure and enhanced oxidation power of ozone, epitaxy has been achieved at significantly lower temperatures than previously reported. Films grown at temperature below 550 {\deg}C show a novel growth mode, which we term "vertical step-flow" growth mode. Epitaxial spinel ferrite films with atomically flat surface over large areas and enhanced magnetic moment can be routinely obtained. Interestingly, the growth mode is independent of the nature of substrates (spinel MgAl2O4, perovskite SrTiO3, and rock salt MgO) and film thicknesses. The underlying growth mechanism is discussed.