C-axis oriented Ba-ferrite thin film with perpendicular anisotropy deposited on Si3N4 substrate

Si₃N₄, a new substrate as well as thermally oxidized SiO₂/Si wafer substrate were used to prepare hexagonal Barium ferrite (BaM) thin films by facing target sputtering system. At substrate temperature (Ts) of 600°C, the intensities of BaM [00l] planes in X-ray diffraction diagrams were much stronger in the case of Si₃N₄ substrate than that of SiO₂/Si wafer substrate. The value of Δθ₅₀ was found about 2.28° for 25-nm thickness of BaM deposited on Si₃N₄. Then, Ts was reduced to 525°C. Perpendicular coercivity (Hc_perp) and squareness ratio (S_perp) were higher in the case of Si₃N₄ substrate even at 525°C. The maximum value of Hc_perp=3.25 kOe and S_perp=0.7 was found for the film of 35 nm. It was found that Si₃N₄ not only reduces the Ts of BaM during in-situ deposition but also increases the perpendicular anisotropy of BaM thin film.