Optimization of parameters and microstructural properties of Ba0.5Sr0.5Co0.8Fe0.2O3-δ thin films grown by pulsed laser deposition (PLD)

Abstract

Ba0.5Sr0.5Co0.8Fe0.2O3 δ thin films were grown by pulsed laser deposition (PLD) in the temperature range from room temperature (RT) to 1073 K and at oxygen pressures from 6.66 to 39.99 Pa in order to produce dense defect-free thin films. Si with a native oxide layer and MgO were used as the substrate materials. The structure of the thin films was highly dependent on substrate temperature, material and oxygen partial pressure, leading to formation of different microstructures - pores, cracks, columnar and fibrous grains. Cracks and delamination of the thin films were observed in dense layers at higher temperatures, while this was not the case with the columnar thin films. Differences in thermal expansion coefficient, phase transformation and oxygen non-stoichiometry of BSCF are possible explanations for the cracking of the dense thin films. Thin films with a columnar structure are positively influenced by annealing inducing grain growth and densification.