Fabrication And Characterization Of Bst Thin Film

Ba_0.6Sr_0.4TiO₃ (BST) thin films are prepared on Pt/TiO₂/SiO₂/Si(001) substrates using sol-gel method, and the related capacitors with Pt electrodes are fabricated using magnetron sputtering method with a shadow mask. Dependence of the structure and physical properties of Si-based Ba_0.6Sr_0.4TiO₃ film annealed by rapid thermal annealing (RTA) at temperatures ranging from 650°C to 850°C is investigated. XRD measurements indicate that the sample annealed at 650°C is amorphous, and the other samples with perovskite structure are polycrystalline. It is found that BST intensity increases with increase of annealing temperature at first; and then decreases with annealing temperature. The dielectric constants of BST samples annealed at 700°C and 750°C, measured at zero-bias electric field, are 166, 193, respectively. It is found that all the prepared BST films show Ohmic-like conduction at low voltages except for the 650°C annealed BST sample, for which Ohmic conduction covers the whole measured electric field range; BST films annealed at 700°C, 750°C and 800°C demonstrate Poole-Frenkel emission conduction at high electric fields, while BST film annealed at 850°C presents Schottky emission behavior.Pt/Ni-Al/Ba_0.6Sr_0.4TiO₃/Ni-Al/Pt capacitors are fabricated on Pt/TiO₂/SiO₂/Si(001) substrates using RF magnetron sputtering and sol-gel methods. Dependence of the structure and physical properties of Si-based Ba_0.6Sr_0.4TiO₃ film with amorphous Ni-Al diffusion barrier layer is investigated. It is found that the maximum dielectric constants of BST samples annealed at 700°C and 750°C, measured at the electric field of -100 kV/cm, are 150, 170, respectively. The amorphous Ni-Al layer can efficiently reduce the leakage current density of Pt/Ni-Al/BST/Ni-Al/Pt capacitors, and the leakage current density is half order of magnitude lower than that Pt/BST/Pt capacitors fabricated by the same condition and method.The study of the Si-based epitaxial Ba_0.6Sr_0.4TiO₃ thin film. Firstly, Ba_0.6Sr_0.4TiO₃ thin films are prepared on Pt/TiO₂/SiO₂/Si(001) substrates by pulsed laser deposition. The maximum dielectric constant of the sample fabricated at 650°C is 260; and the dielectric loss, tunability, leakage current density, measured at the electric field of -417 kV/cm, are 0.055, 23% and 2.9×10-5 A/cm2, respectively. Secondly, Highly oriented CeO₂ buffer layers are prepared on Si(001) substrates by PLD technology using two-step growth method, which establish the foundation for the Si-based epitaxial BST thin film.