The Epitaxial Growth And Its Dielectric Properties Of Ba_1-xSr_xTiO₃ Thin Films By Sol-gel Method

Due to the splendid ferroelectric and dielectric properties,Ba1-xSrxTiO3(BST)thin films have already shown very favorable prospects in Dynamic Random Access Memory and tunable microwave devices.It is very necessary to prepare a bottom electrode on the bottom surface of BST thin films in practical applications.However,some conventional electrode,such as Pt,whose poor adhesion to the substrate and the diffusion at high temperature limited its applications seriously.YBa2Cu3O7-x(YBCO)attracted great attention since the advantages of its great conductivity,low microwave loss and its perovskite structure.Owing to the easier control of the reaction,large-scale production and lower costs,the sol-gel method was widely used.Therefore,sol-gel method was used to prepare BST/YBCO multilayer films with epitaxial structure on LaAlO3(LAO)substrate.The optimum heat treatment process was explored,and the dielectric properties were studied at both room and low temperature.The following sections were included:Firstly,YBCO thin films with high quanlity were prepared on LAO substrate,and then a certain thickness of the BST films were prepared on YBCO/LAO via dip-coating.As revealed by X-ray diffraction,scanning electron microscopy,and R-T test,a better heat treatment process of BST thin films were obtained.Results showed that better grains were got with heat treatment at 120? for 10 min,then 10 min at 350?,10 min at 600?,60 min at 750?,while biaxially textured BST/YBCO thin films were got.Secondly,dielectric properties were tested of undoped BST/YBCO thin films.And the results showed that dielectric loss was 0.128 at 80 K.Finally,BST thin films were doped of Ce in order to solve the problem of the greater dielectric loss of BST thin films which were prepared previously,and Ce doped at the amount of 0.5,1.0,1.5,2.0 mol%.The results showed that:dielectric loss decreased after doping.The of 0.5,1.0,1.5,2.0 mol%.The results showed that:dielectric loss decreased after doping.The best dielectric properties performed when Ce doped with the amount of 1.5mol%.The value of dielectric loss can be as low as 0.0065,the tunablity was up to 51.70%the factor of merit reached 79.53 at 80 K.