Preparation And Properties Of Bismuth Ferrite-based Multiferroic Film

BiFeO₃（BFO）has received extensive attention due to its multiferroic and optical properties at room temperature.It is well known that doping can improve the application of limiters such as high leakage current density and weak ferromagnetic properties in devices.Therefore,this study based on BFO prepared and characterized La-doped（A site）,Ni-doped（B site）BFO films and composite films of BFO and Zn O respectively.The microstructure,surface morphology,multiferroic,and optical properties were studied and analyzed.The main results are as follows:Firstly,Bi_1-xLa_xFe O₃（x=0,0.04,0.08,0.12）thin films were prepared on Pt/Ti/SiO₂/Si and FTO glass substrates by sol-gel method,respectively.Spectra and band gaps were analyzed.The experimental results show that doping reduces the leakage current density and improves the multiferroic property.The film with a doping ratio of 0.08 has the best ferroelectricity and has a saturation polarization（2P_s）of about 28.4μC/cm².When the doping ratio is 0.12,it has the best ferromagnetism.In addition,with the increase in doping amount,the absorption spectrum shows a red-shift phenomenon and the bandgap gradually decreases to 2.16 e V.Secondly,in order to improve the ferromagnetism of the films,La and Ni co-doped Bi_0.92La_0.08Fe_1-yNi_yO₃（y=0,0.02,0.04,0.06,0.08）films were prepared.The experimental results show that co-doping can effectively improve the saturation,remanent polarization and magnetization.The observed value of the maximum 2P_sreaches 48.08μC/cm²,and the maximum remanent polarization（2P_r）reaches 18.94emu/cm³.With the increase in Ni doping amount,the red-shifted optical band gap of the absorption spectrum decreases and drops to 2.10 e V when the doping concentration is 6%.Finally,Zn O,BFO/Zn O and Zn O/BFO composite thin films were prepared by sol-gel method on Pt/Si/SiO₂/Si and FTO glass substrates,respectively,and their ferroelectric,ferromagnetic,and optical properties have been explored.The results show that the performance of the BFO/Zn O composite film is better than that of the Zn O/BFO composite film,mainly in the larger saturation polarization（2P_s=46.7μC/cm²）,saturation magnetization（2M_s=68.87 emu/cm³）.Therefore,based on previous results we tried to prepare Bi_0.92La_0.08Fe_0.94Ni_0.06O₃/Zn O composite film,followed by tested and characterized the abovementioned properties.The test results show that its 2P_sreaches 51.46μC/cm²,and the bandgap is reduced to 2.08 eV.