Synthesis And Properties Of Ni-doped BST Thin Films

Barium strontium titanate is the complete solid solution of BaTiO3and SrTiO3, and it is ABO3perovskite structure. It is widely applied in the various fields such as dynamic random access memories, Pyroelectric infrared detectors, tunable microwave devices and phase shifters, due to its high dielectric constant, low dielectric loss, high breakdown electric field, low leakage current, excellent pyroelectric property, and low extinction coefficient. In recent years, as the rapid development of VLSI process, BST thin films applied in integrated devices has attracted great interest. It is a key problem that how to prepare the barium strontium titanate thin films with high crystalline and superior electric and optical properties.In this dissertation, Ba0.6Sr0.4TiO3(BST)films were synthesized by sol-gel method, and different amount of Ni was doped. Then the influence of the doping to the crystalline quality and the photoelectric property of the BST thin film crystal was systemic researched. The main results and conclusions can be summarized as following:(1). The pure BST precursor and those with different concentration of Ni doping were successfully made after many times experiments. The thin films of pure BST and the ones with different amount of Ni doped were deposited on LNO, Si, and quartz substrates, respectively.(2). The X-Ray Diffraction (XRD) was used to study the microstructure of the BST thin films with different addition of acetylacetone and Ni doped, and on different substrates. The Scanning Electron Microscope (SEM) was used to study the surface and section of BST thin films on LNO substrates. The influence of Ni doped on the3D surface of BST films was researched by using Atomic Force Microscope on LNO substrates. The results illustrated that the BST film on LNO substrates with10percent Ni doped performes the best quality of crystal and has more flat surface and weak larger grain size.(3) The ferroelectric and dielectric properties of Ni doped BST thin films were studied. The results show that Ni-doped can increase the dielectric constant, and decrease dielectric loss. Ferroelectric property of10mol%Ni-doped BST thin film is the best, and Pr is about2.8μC/cm2. In a word, Ni doping can effectively improve the ferroelectric and dielectric properties of BST thin films.(4)The Raman spectroscopy implys that Ni-doped can affect the microstructure of the BST thin films. Spectroscopic ellipsometry shows that Ni-doped can decrease the refractive index of BST thin films. By transmittance spectra, we the optical band gap was obtained, about4eV.