Modification of Band Structure by Oxygen Filling in Epitaxial La_0.88Sr_0.12MnO_3–x Thin Films

Oxygen stoichiometry is a critical factor in transition-metal oxides, such as manganites, as it has a substantial influence on their electronic and magnetic properties through the generation of oxygen vacancies. However, the significance of oxygen stoichiometry is often underestimated in manganite thin films. In this study, we explore the formation of oxygen vacancies within La 0.88 Sr 0.12 MnO 3 (LSMO) under standard thin-film deposition conditions and elucidate how these vacancies can be effectively filled through exposure to high oxygen partial pressure ( P O 2 ) on the order of several hundreds of Torr during the cooling phase. The oxygen replenishment process has a profound impact on the electronic band structure, resulting in alterations in electron occupancy near the Fermi level. This phenomenon is observed by optical spectroscopy and analyzed by density functional theory calculations. These findings underscore the indispensable nature of postdeposition oxygen annealing steps to attain stoichiometric LSMO thin films.