Optical response of oxygen deficient La0.7Sr0.3MnO3 thin films deposited by pulsed laser deposition

The optical response of 200nm thick La0.7Sr0.3MnO(3−δ) films, deposited by pulsed laser deposition on amorphous silica substrates heated at nearly 600°C, under different oxygen pressures (0.1Pa, 0.5Pa, 1Pa, 5Pa and 10Pa), is reported. The effects of the oxygen non-stoichiometry are investigated at room temperature dealing with the absorption coefficient and the Tauc's plot method rather than conventional optical conductivity. The absorption curves are evaluated by an algorithm able to realistically describe the behavior of thin films without exploiting numerical extrapolations or simplified theoretical models or ab-initio calculations. Optical features, tunable by the growth oxygen pressure, are discussed based on the known theoretical and experimental scenario. •Overview of the La0.7Sr0.3MnO3 basics to highlight basic questions to be assessed.•Optical analysis by the absorption coefficient rather than optical conductivity.•Realistic absorption response that avoids numerical refinements and simulations.•Analysis of the role of oxygen vacancies in tuning the electronic dispersion.•First investigation of direct and indirect transitions by the Tauc's plot.