Growth of NiTiO3 polymorphs on silicon substrates by radio frequency sputtering

Nickel titanate (NiTiO3) is known to exhibit three types of structures which differ in terms of cationic ordering, namely ilmenite (IL), LiNbO3 (LN), or corundum (CR) structures. In this study, radio frequency sputtering using Ar/O2 reactive plasma has been used for the insitu crystallization of NiTiO3 thin films on Si(1 0 0) substrates heated at various temperatures (in the range 400 °C-650 °C). The stabilization of the different NiTiO3 polymorphs as a function of the substrate’s temperature are discussed basing on X-ray diffraction (XRD), Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) characterizations. Depositions at 650 °C enabled to obtain IL thin films. Depositions at lower temperature (400–600 °C) led to the formation of mixture of IL/LN/CR structures. Whatever the substrate temperature, films are grown with a [00W] fiber texture. Post Annealing of the IL/LN/CR NiTiO3 thin films at 800°C resulted in its recrystallization into the IL structure, while preserving the [00W] fiber texture. Density functional theory (DFT) simulations aided in predicting Raman spectra for LN and CR phase. The combination of XRD, Raman spectroscopy, and HRTEM offers a detailed understanding of phase transitions and morphological changes, essential for optimizing the properties of NiTiO3 films for various applications.