The Fabrication Of Bi-based Oxide Thin Films By Molecular Beam Epitaxy Method And Studies Of Their Physical Property

In this dissertation, vacuum annealing furnace was used to smelt Sr as the evaporation beam source of the furnace. The ozone condensing device was adopted to get high concentrations ozone as the oxide source. Atomic force microscope was used to obtain the evaporation rates of Bi, Sr, Ca, and Cu elements. Then, Bi-based oxide thin films were prepared by the molecular beam epitaxy (MBE) method. Firstly, Bi2Sr2CuO6+δ thin films were prepared, which were characterized by simple structure and wide temperature into phase.Secondly, Bi2.1CaySr1.9-yCu06+δ and Bi2Sr2CaCu2O8+δ (Bi-2212) thin films were also investigated based on the obtaining of Bi2Sr2CuO6+δ films and taking the evaporation rate of metal sources and reference adsorption coefficient into account. Finally, the structure, surface morphology, crystallinity and electrical properties were investigated by several detection means. The detail results of the dissertation are as follows:(1) The ozone condensing device was adopted as the oxide source to prepare BSCCO thin films by MBE. The temperature of silica gel was maintained at-80±1℃. The high ozone concentration(>90mol%) was maintained more than4h when the pressure of the condensed device was1.5×103Pa. There was a liner relationship between the evaporation rates of Bi, Sr, Ca and Cu elements and the temperature of every effusion cell, which fulfill the expression of Clausius-Clapeyron equation.(2) Bi2Sr2Cu06+δ thin films with high-quality were prepared. For Bi2.1CaySr1.9-yCu06+s thin films, the length of c-axis decrease with the increase of y value, and the conductivity of the film was different with different y values. When y was0.8, it could obtain Tc,onset=90K.(3) For Bi-2212thin films, it was found that the phase purity was the highest and the crystalline quality was better when Bi-2212thin films was prepared on the MgO (100) single crystal substrate under the conditions of substrate temperature at699℃, ozone partial pressure at2.2×10-4Pa. With the same ozone partial pressure, reducing the substrate temperature and with the same substrate temperature, increasing ozone partial pressure, it was a similar process for Bi-2212into Phase; The phase purity and crystallization quality of Bi-2212film with SrTiO3(100) single crystal substrate were improved compared with MgO (100) as the mismatch decreases; Bi-2201buffer layers with different thickness were deposited between the MgO(100) substrates and Bi-2212thin films and the Tc was increased because of lower lattice mismatch.