The role of oxygen vacancies in ferroelectric zirconia thin films
|In the latest years, defect engineering provided a powerful tool for tailoring nanomaterials for several applications, and to switch from nanoscale to atomic-scale electronics. Among nanomaterials that have been modified with this approach are ferroelectric oxide thin films, structures that are compatible with the present semiconductor technologies, provide robust ferroelectric polarization and have been then used for ferroelectric memory and field-effect transistors, energy storage devices and sensors.
To obtain a robust ferroelectric polarization, several polycrystalline thin films require an initial wake-up pre-cycling. Epitaxial thin films seem to be an exception; however, spontaneous polarization observed in these structures is not fully understood. Dr José P. B. Silva, Dr Veniero Lenzi, Prof. Luís Marques from the University of Minho, the University of Cambridge, together with Czech and Romanian CERIC Partners exploited X-ray Photoelectron Spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) instruments, available respectively at the Czech and Romanian CERIC Partner Facilities, to study this mechanism in ZrO2 thin films.
They then demonstrated through density functional theory simulations and by investigating the structural properties, chemical composition and ferroelectric properties of the films before and after an annealing at moderate temperature (400 °C) in an oxygen-rich environment, that oxygen vacancies are a key factor for stabilizing the polar rhombohedral phase and also a possible source of ferroelectric polarization.
ORIGINAL ARTICLE: