Fabrication And Ferroelectric Properties Of BNT And BFO And BNT/BNT Composite Thin Films

As a novel non-volatile random access memory, ferroelectric random access memory (FeRAM) has many advantages and application value compare with the traditional memories. Because ferroelectric thin film is the most important part of ferroelectric random access memory, fabrication high quality ferroelectric thin film is very important for the widely application of ferroelectric random access memory. In this thesis, we have successfully fabricated BNT (Bi_3.15Nd_0.85Ti₃O₁₂) thin films, BFO (BiFeO₃) thin films and BNT/BFO Composite thin films on substrate of Pt(111)/Ti/SiO₂/Si(100) by a chemical solution deposition technique (CSD). We vary the condition of the fabrication, and the effect of annealing temperature, heating-up rate, doping, annealing atmosphere and interfacial effect were studied.After exam and analysis the crystal structures and electric properties of BNT thin films, we can conclude that: the surface of the BNT thin films are dense, smooth and well crystallized, the thickness of the film is about 360 nm; the best annealing temperature of the BNT thin films is 750 oC; in the process of the fabrication of BNT thin films, the heating-up rate can affects the orientation of the film grows and the quality of the film; the ferroelectric properties of the BNT thin films were found to be remarkably sensitive to the post-annealing treatment, which is because of the present of an interface layer between the film and the metal electrode.The BFO thin films fabricated by CSD were well crystallized, the surface of the BFO thin films are dense and smooth. We found that the BFO thin films can have a lower leakage density and better ferroelectric properties by doping, the sample films by doping La in A site have better electric properties than the sample films by doping La in A site and Mn in B site both. The samples annealing in the oxygen have better properties than the samples annealing in the air.We successfully fabricated BNT/BLFMO composite thin films on substrate of Pt(111)/Ti/SiO₂/Si(100) by CSD. We found that fabricating composite thin films which the thickness ratio of BNT and BLFMO is appropriate can significant reduce the leakage density and improve the ferroelectric properties. When the thickness of the sample film is about 350 nm and the ratio of BNT and BLFMO is about 5:3, the leakage of the sample is about 10^-3 A/cm², and saturated hysteresis loop were observed, the remanent polarization value (2Pr) is 80.9μC/cm² when the hysteresis loop is saturation.