The Preparation And Research Of High-quality YIG Films By Radio Frequency Magnetron Sputtering

With the evolution of modern microwave technology,microwave ferrite devices used in communication system core part plays an indispensable role in mobile communication.The microwave devices are based on a certain magnetism,high resistivity on the basis of microwave ferrite materials.Yttrium iron garnet(YIG)is widely used because of its good spin magnetic,high resistivity and low resonance linewidth in the numerous microwave ferrites.With the development of monolithic microwave integrated circuit(MMIC),the miniaturization of the device has become an inevitable trend of microwave devices development.The YIG ferrite thin films and thick films were prepared on MgO substrate by rf magnetron sputtering.The influences of different sputtering pressure,sputtering power and oxygen partial Pressure on the surface morphology,deposition rate,microstructure and magnetic properties of YIG thin films on MgO substrate were studied by SEM,Profiler,XRD and VSM.Also,the influences of different annealing temperature,annealing time and cooling rate on YIG thick films were studied and analysed.The experimental results indicated that the performance of YIG thin film is affected by the sputtering parameters.The deposition rate increases and then decreases with the increase of sputtering pressure and sputtering power.The surface roughness of YIG thin film on MgO substrate increases with the increase of sputtering pressure.However,the surface roughness of YIG thin film first increases then decreases with increasing sputtering power on MgO subsrate.High quality YIG films which own smooth,continuous surfaces and uniform average grain sizes were obtained at 1.5Pa and 200W.We concluded that the YIG films with good crystallinity possess optimal saturation magnetization of 133emu/cm3,closed to the theoretical value of bulk YIG under the same condition.The crystallinity and grain size of YIG thick films on MgO substrate depend on the annealing temperature and annealing time.Also,the degree of cracking of YIG thick films depend on the cooling rate.High quality YIG films which own smooth,continuous surfaces and uniform average grain sizes were obtained when the annealing temperature was 700°C,the annealing time was 4 hours and the cooling rate was 0.5?/min.In this case,the saturation magnetization of YIG thick films was 129.1emu/cm3,closed to closed to the theoretical value of bulk YIG.As the film thickness increases,the crystallinity and magnetic of YIG films become better and better until the film thickness reaches 3?m.