Substrate damage and incorporation of sapphire into barium hexaferrite films deposited by aerosol deposition

Barium Hexaferrite (BaM) grown on sapphire substrate by aerosol deposition is investigated in a subtractive wedge series to determine the extent of energetic substrate damage and indentation. Energy dispersive x-ray spectroscopy (EDS) mapping reveals Al2O3 particulates ejected from the substrate surface during growth. The concentration of particles is higher at the substrate-film interface but persists throughout the 6 mu m thick film. An estimate of the indentation depth (similar to 600 nm) was agreed upon using two EDS techniques (line scan analysis and substrate surface reconstruction by areal integration). X-ray diffraction patterns show peak polycrystalline Al2O3 intensity in 1.5 mu m thick wedges and a decrease at higher thicknesses, confirming that Al2O3 particulate density decreases further from the substrate. Here, magnetic characterization showed decreased magnetic moment compared to bulk and thickness dependence consistent with the fractional increase of Al2O3 content in the films. X-ray absorption at the Fe L3 edge suggests a reduction of material close to the surface, but this reduction appears secondary in magnitude to the effect of damage from deposition.