Research Of Preparation And Interfacial Structure On The Alternately Doped Ba_0.6Sr_0.4TiO₃Thin Films

Barium strontium titanate (Ba1-xSrxTiO3, BST) thin film is a typical ferroelectricmaterial widely used with a thickness range from nm to μm. Under the applied voltage,the dielectric constant of BST film can be adjustable in a certain range, which can makethe tunability higher. The tunability of BST thin film is an important index to measurethe nonlinear, so the film of BST is a good candidate for tunable microwave devices,such as filter and phase shifter. Moreover, those tunable microwave devices also requirethe film of BST with very low loss. Therefore, it is very important to explore new BSTthin film with high tunability and low dielectric loss.In order to study the dielectric properties of BST thin film, the characteristic of theinterfaces between the thin films of Ba0.6Sr0.4TiO3prepared by the method of Sol-gel isstudied. Combined with the study on the dielectric properties of BST thin films, thefactors of doped alternately BST thin film are stuied,which include the order ofalternately doping, the doping concentration and the layer of the BST film. The phaseatructure, surface morphology and cross section structure of BST film are studied usingthe modern materials analysis methods of XRD, XPS, SEM. and their impacts on thedielectric properties of alternating doped BST thin film are analysised.First, the surface and cross-sectional characteristic of the samples of undoping,doping with one element and alternatively doping BST films are analysised using themethod of SEM. And the difference of interfacial structure between the BST films underdifferent style of doping are studied.Secondly, in order to study the interface characteric, the dielectric properties ofalternately doped BST thin films are studied and the result shows that the tunability ishigh in alternately doped BST thin films while the dielectric loss is lower the tunabilityand dielectric loss of the BST thin film are explained using the phase structure of XRD,the chemistry element state of XPS and the interfacial structure of SEM.Finally, in order to study the dielectric propertities of the alternately doped BSTfilm, the doping concentration and the layers of the films are studied combined with theinterfacial structure between films, the chemistry state of element on the surface and the phase structure. The results show that the synthesized dielectric properties of thealternately doped BSTthin film on the doping concentration of10mol%are best, whichhave tne higher tenability and the lower dielectric loss. The dielectric properties, thedielectric constant under the bias voltage and the characteristic of frequency areanalyzed in the study of the effects of the layers on the Mg/K-BST thin films and thestructure and the dielectric properties of even layer of K/Mg-BST thin films are alsostudied.