The Influence Of Substrate,impurity And Buffer Layer On The Properties Of Ba_0.6Sr_0.4TiO₃ Thin Films

800 nm Ce O₂:B_a0.6Sr_0.4Ti O₃(BST)composite film has been prepared on the La Al O₃(001)single crystal substrate using magnetron sputtering with pulsed laser deposition system.The Pt/Ce O₂:BST/La Al O₃ composite film interdigital capacitor was successfully constructed on the La Al O₃(001)single crystal substrate by the photolithography,lift-off and RF magnetron sputtering technique.The Ce O₂:BST composite film interdigited capacitors of the volume fraction ratio from 1:20 to 1:200.It is found that doping of Ce O₂ can be effectively modulated dielectric properties of BST thin film.Under 40 V bias voltage,tuning rate appear to first increase then decrease with the increase of doping amount,dielectric loss basically remain unchanged.The optimal proportion of Ce O₂:BST composite film is 1:80.At40 V bias voltage,the tunability is 39.35%,the dielectric loss is 0.033,the quality factor is12.07.Under the optimal proportion of Ce O₂:BST composite film,we prepared Four types of Ce O₂:BST composite films.Then Pt interdigited capacitors were constructed by lithography and RF magnetron sputtering technique.After the test of the Ce O₂:BST composite film:Beaded type have the best dielectric properties.Under 40 V bias voltage,the tunability is48.45%,the dielectric loss is 0.025,the quality factor is 19.38.BST film has been prepared on the La Al O₃(001)and Mg O(001)single crystal substrates using pulsed laser deposition system.The structure and surface morphology of the BST films are characterized by XRD and AFM.The results show that:the two kinds of BST thin film are epitaxial grown;the average grain size of BST films grown on La Al O₃ and Mg O structure are42 nm and 52 nm,respectively.Pt/BST/La Al O₃ and Pt/BST/Mg O interdigital capacitors are successfully constructed.The LCR meter is used to test the dielectric properties of Pt/BST/La Al O₃ and Pt/BST/Mg O.The result shows that:Pt/BST/Mg O have higher tenability(39.68%),lower dielectric loss(0.029).Pt/BST/Mg O have smaller frequency dependence,and the device can be used in a wider range of frequenciesFirst step,we use magnetron sputtering prepared epitaxial Mg O buffer layer on sapphire(0001)single crystal substrate.The second step,BST film are grown on sapphire(0001)single crystal substrate and deposited Mg O buffer layer on a sapphire substrate,respectively,using pulsed laser deposition method.The third step,Pt/BST/Al₂O₃ and Pt/BST/Mg O/Al₂O₃interdigital capacitors are successfully constructed.X-ray diffraction(XRD)result shows that:the BST film grown on Mg O buffer layer is epitaxial structure.And the LCR meter test result shows that:the BST film grown on Mg O buffer layer have better dielectric properties.