Investigation Of Properties Of Epitaxial Pb(Zr_0.4Ti_0.6 )O 3 And BiFe_0.95 Mn_0.05 O₃ Films Prepared By Sol-Gel Method

Pb(Zr_0.4Ti_0.6)O₃ and BiFe_0.95Mn_0.05O₃ thin film have been successfully prepared by Sol-Gel method, and the related ferroelectric capacitors with Pt or SrRuO3 top electrodes are fabricated using magnetron sputtering method with a shadow mask. The microstructure and morphology of the thin films as well as the ferroelectric and dielectric properties of the capacitors have been investigated using various techniques, such as x-ray diffraction (XRD), atomic force microscopy (AFM), ferroelectric tester (Precision LC Unit) and LCR meter. The main results are as follows:SrRuO3 thin film is fabricated on (001) SrTiO₃ substrate using RF magnetron sputtering method. Influences of deposition temperature on the structural and physical properties of SrRuO3 thin film are studied using XRD, AFM and Four-probe tester. It is found that SrRuO3 thin film is polycrystalline when the deposition temperature is lower than 550℃, it is epitaxially grown on SrTiO₃ substrate when the growth temperature ranges from 550 to 650℃, and nice surface morphology and low resistivity of ⁰.7 m? . cm are found for the SrRuO3 films prepared at 600℃and 625℃.Ferroelectric Pb(Zr_0.4Ti_0.6)O₃ heterostructures are fabricated on Pt/Ti/SiO2/Si substrates by Sol-Gel method with or without SrRuO3 conductive layer. Influences of SrRuO3 conductive layer on the structural and physical properties of Pb(Zr_0.4Ti_0.6)O₃ films, crystallized by rapid thermal annealing, are studied by XRD and ferroelectric tester (Precision LC unit). The remnant polarizations of the Pt/Pb(Zr_0.4Ti_0.6)O₃/Pt and SrRuO3/Pb(Zr_0.4Ti_0.6)O₃/SrRuO3 heterostructure are 17.4μC/cm₂ and 28.3μC/cm₂ at 5 V, respectively. The net polarization decrease 70% and 20% for the two capacitors respectively after 10₁0 reversal.BiFe_0.95Mn_0.05O₃ and BiFeO3 films are grown on platinized Si substrates using Sol-Gel method combining with rapid thermal anneals. It is found that 5% Mn doping can greatly impact the microstructural and physical properties of BiFeO3 film. The remnant polarization of the BiFe_0.95Mn_0.05O₃ capacitor is 50.4μC/cm₂ at 175 kV/cm. The leakage current density of BiFe_0.95Mn_0.05O₃ film is higher than that of the BiFeO₃ film at low electric field, but at 175 kV/cm, it is about 5×10^-3 A/cm², much lower than 4×10^-1 A/cm² of the BiFeO₃ film. Furthermore, better dielectric and magnetic properties are found for BiFe_0.95Mn_0.05O₃ film. BiFe_0.95Mn_0.05O₃ heterostructures are fabricated on Pt and SrRuO₃ bottom electrodes by Sol-Gel method. Influences of SrRuO₃ conductive layer on the structural and physical properties of BiFe_0.95Mn_0.05O₃ films are studied. It is found that SrRuO₃ bottom electrode is favorable for the crystallization of the BiFe_0.95Mn_0.05O₃ film. The breakdown field of SrRuO₃/BiFe_0.95Mn_0.05O₃/SrRuO₃ heterostructure is higher than that of Pt/BiFe_0.95Mn_0.05O₃/Pt heterostructure. The leakage current densities of the two capacitors are 8.3×10-4 A/cm2 and 8.0×10-3 A/cm2 at 172 kV/cm, respectively.Preferred (00l) growth Pb(Zr_0.4Ti_0.6)O₃ film and epitaxial BiFe_0.95Mn_0.05O₃ film with room-temperature switching properties are fabricated on SrTiO₃ substrates with a SrRuO₃ buffer layer by sol-gel combined with rapid thermal annealing. The Pb(Zr_0.4Ti_0.6)O₃ films annealing at 530～580℃show (00l) preferred growth, but the different ferroelectric properties can be observed. The BiFe_0.95Mn_0.05O₃ capacitor show saturated hysteresis loop, and the remnant polarization is 51.8μC/cm² at 455 kV/cm. The net polarization keeps on 95.2μC/cm² after 10¹0 reversal.