Preferential Orientation Growth Of Layered Perovskite Bi₅Ti₃FeO₁₅ Multi-iron Thin Films On Metal Bottom Electrodes

At present,the design of novel single-phase room-temperature multiferroics materials has attracted wide attention.The preparation of single-phase room-temperature multiferroics thin films will conform to the trend of miniaturization and multifunction of devices.It is a challenge to grow perovskite multiferroics thin films directly on the metal bottom electrode in uniform orientation.In this paper,single-phase multiferroics materials Bi₅FeTi₃O₁₅ synthesized by inserting the antiferromagnetic group BiFeO₃ into the ferroelectric Bi₄Ti₃O₁₂ matrix.More importantly,the process of controlling the orientation growth of Bi₅FeTi₃O₁₅ thin films directly on metal electrodes was explored.The topic is novel,which has both scientific significance and practical value.The main results and conclusions are as follows:1.Bi₅FeTi₃O₁₅ thin films with single-phase four-layer perovskite structurewere prepared directly on?111?Pt/Ti/SiO₂/Si substrates by a sol-gel method,indicating the antiferromagnetic BiFeO₃ has been successfully inserted into three-layer ferroelectric material Bi₄Ti₃O₁₂.2.The effects of preparation of precursor solution and heat treatment on the near-a/b axis orientation of Bi5FeTi3O15 films were discussed.The orientation of near-a/b axis is higher when the concentration of precursor solution is 0.1 mol/L,the ratio of solvent and chelating agent is 1:1 and the aging time is 24 hours,and the films was annealed at 750?C with a heating rate of 100?C/s in heat treatment process.3.The 59.2%near-a/b-axes oriented,randomly oriented and 87.8%near-c-axis oriented Bi₅FeTi₃O₁₅ thin films were prepared directly on?111?Pt/Ti/SiO₂/Si by a sol-gel process.The three oriented films exhibited significant ferroelectric and dielectric anisotropy as expected.The remanent polarization 2Pr of near-a/b-axes oriented film,randomly oriented film and near-c-axis oriented film was 44.6?C/cm²,29.3?C/cm² and12.4?C/cm²,respectively;at 100 kHz,the dielectric constants of near-a/b-axes oriented film,randomly oriented film and near-c-axis oriented film were 592,446 and 239,respectively.The saturation magnetization Ms of the near-a/b-axes oriented film,randomly oriented film and near-c-axis oriented film were 0.21 emu/cm³,1.12emu/cm³ and 0.29emu/cm³,respectively.