Effect of oxygen vacancies on the structural and transport properties of SrTiO3 thin filmsexperiments and ab-initio calculations

Resumo

This PhD Thesis deals with the study of the effects of oxygen vacancies and strain on the structural and transport properties of strained SrTiO3 thin films, fabricated by pulsed laser deposition technique. In addition, the Thesis presents a novel approach combining experiments and ab-initio simulations to investigate and understand the underlying mechanisms that link oxygen vacancies and the properties of this material. We began by studying the thermodynamics of oxygen vacancy formation depending on the strain, examining the necessary conditions to achieve stoichiometric samples. Moreover, we determine strain dependence of the formation enthalpy of oxygen vacancies in the films. Furthermore, we perform a detail study about how the strain affects the octahedral rotation pattern of SrTiO3 thin films and discuss the role of strain, structural distortions and oxygen vacancies in the appearance of a ferroelectric-like response in SrTiO3 samples. Lastly, we study the influence of oxygen vacancies in the transport properties of the films, discussing the similarities in the observed phenomenology with the one reported in the famous LaAlO3/SrTiO3 interface.