Perpendicular orientation of Ba-ferrite thin film with Al top layer and underlayer

The effectiveness of Al top layer and Al underlayer on the crystallization temperature of hexagonal Barium ferrite (BaM) thin film was studied. All of the BaM films were deposited on Si (111) substrate without any substrate heating. Then, flash annealing was carried out to crystallize the BaM film. A very ultrathin Al top layer of 5 nm was helpful for improving the crystallographic properties of BaM thin film, but the effect was more intensified when Al was used as an underlayer instead of a top layer. From the X-ray diffraction (XRD) diagram, the c axis orientation of BaM film with an Al underlayer was confirmed even though the annealing temperature was reduced to 650°C. The saturation magnetization value also supports the XRD data. From the experimental data, it was found that the Al underlayer can reduce the crystallization temperature of BaM in the range of 600°C to 625°C by flash annealing for 1 min. The nanocrystalline structure of the Al underlayer promotes the crystallization of BaM very remarkably and hence reduces the crystallization temperature.