Research On Preparation Technology Of M-type Barium Ferrite Films

Due to its very high magnetocrystalline anisotropy field, high remenentmagnetization, good chemical stability and high mechanical hardness, the M-typehexageonal barium ferrite (BaM) film is quite suitable for applications of microwave/millimeter-wave ferrite devices and high density pendicular magnetic recording. Theeffective uniaxial magnetocrystalline anisotropy filed of BaM is about17kOe. It isthis strong built-in field that makes the BaM films can work at millimeter wave bandwith no need of external bias fields, and, thereby, makes the research field of BaMmaterials quite promising. In this dissertation, radio frequency (RF) magnetronsputtering technique had been used to investigate the deposition processes for BaMfilms with strong c-axis orientation perpendicular to the film plane.BaM films were prepared by RF magnetron sputtering technique, and theproperties of films were characterized by scanning electron microscope, vibratingsample magnetometer and X-ray diffractomer. The sputtering conditions andpost-annealing conditions were investigated. The effect of film thickness for BaM/Si(100) films on the crystallites orientation and magnetic properties was studied. At last,by depositing BaM film on different kinds of substrate or underlayer, the changes ofcrystallites orientation and magnetic properties of the BaM films had been discussed.And BaM films with strong c-axis perpendicular orientation had been achievedfinally.As a result, the BaM films deposited with a radio frequency power of110W, agas pressure of1.1Pa, a substrate temperature of300℃and a post-annealingtemperature of800℃can get the best property. The c-axis orientation of thecrystallites for BaM/Si(100) films deteriorate gradually with the increase of filmthickness. And when the film thickness is large enough, the BaM/Si(100) films tend tobe isotropic with random oriented crystallites. The hexageonal AlN underlayer canenhance the c-axis perpendicular orientation of BaM film effectively. TheBaM/AlN/Si(100) and BaM/AlN/SiO2/Si(100) films can still have a high anisotropyfield around15000Oe even with a film thickness of300nm, which is much better thanthe BaM/Al2O3(001) films. Compared with Al2O3(001) substrate, AlN underlayer is more costless, easy to prepare, whats more, compatible with semiconductorstechnology. This have a great significance on the aplication of BaM films tomicrowave monolithic integrated circuit.