Microstructures And Properties Of Multilayer Iron Garnet Magneto-Optical Film By Pulsed Laser Deposition

A single-step PLD method with subsequent rapid thermal annealing has been proposed to develop YIG( Y3Fe5O12), Ce:YIG( Ce0.6Y2.4Fe5O12) and Bi:YIG( Bi1Y2Fe5O12) iron garnet multilayers on the silicon substrate. X-Ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), atomic force microscope(AFM), scanning electron microscope(SEM) and transmission electron microscope(TEM) were used to characterized the phase purity and chemical component as well as the surface morphology and interface structure.The magnetic property at room temperature varying similarly with Faraday rotation and optical transmittance spectra were measured. The variation tendency of microstructures and properties of the as-deposited films was proposed.Single-step pulsed laser deposition at both room temperature and 650 oC together with subsequent rapid thermal process at 800 oC in 5 minutes has made it possible to acquire cerium-substituted bilayers with the thickness ration of 2:1 and different sequence. The cerium-substituted yttrium iron garnet films deposited at room temperature and 650 oC was polycrystal iron garnet structure, and the RMS roughness at 20 μm ×20 μm square was below 1 nm which meant a good surface quality.The saturation magnetization was around 135 emu/cm3 close to that of single crystal YIG at 140 emu/cm3. The film with another deposition sequence as YIG/Ce:YIG/Si obtained similar phase structure, surface morphology and magnetization property, which meant the single-step PLD attempt will enable the substituted layer to contact the photonics platform directly leading to a dramatic improvement of the device performance.According to XRD spectrum, it was found that Ce:YIG/YIG/Si film with thickness ratio which was larger than 6:1 was not fully crystallized during the deposition at 650 oC and heat treatment at 800 oC in 5 minutes. The saturation magnetization decreased due to the imcomplete crystallization. And TEM suggested that the noncrystallization portion of 8:1 films was not distributed at the surface evenly but dispersed into the films randomly.The bismuth-substituted film deposited at room temperature was also iron garnet structure while the film deposited at 650 oC had other phase like YFe O3 or YFe2O4. There were cracks or particles on the surface of the respective films. And the surface roughness was below 1 nm and higher than 6 nm respectively. The saturation magnetization of films deposited at room temperature was a little lower than cerium-substituted film and the ones deposited at high temperature was even below 50emu/cm3. Moreover, the Bi YIG/YIG/Ce:YIG/Si film was deposited at room temperature. It obtained pure iron garnet structure and a high-quality surface where the roughness was below 1nm. The saturation magnetization at room temperature was 135 emu/cm3.