优异Y-BST薄膜的设计、制备及介电性能

Design, Preparation and Dielectric Properties of Excellent Yttrium-Doped Ba_(0.6)Sr_(0.4)TiO_3 Films

就(Ba+Sr)/Ti的原子摩尔比例、掺杂浓度、薄膜厚度等优化设计钇掺杂Ba0.6Sr0.4TiO3(Y-BST)薄膜,用改进的溶胶-凝胶(sol-gel)法在Pt/Ti/SiO2/Si基片上制备Y-BST薄膜,研究该薄膜的结构及介电性能。X射线衍射(XRD)表明,薄膜均为立方钙钛矿多晶结构,主要沿(110)晶面生长。随(Ba+Sr)/Ti比值的增加,BST薄膜衍射峰强度增加,晶化增强;Y-BST薄膜随掺杂浓度(>1%摩尔比)的增加,衍射强度减弱,晶化减弱,但随薄膜层数的增加,衍射强度增强,晶化增强。40V和100kHz的电压-电容测试表明,(Ba+Sr)/Ti比值为0.9及掺杂浓度为2%摩尔比的8层Y-BST薄膜具有最优综合介电性能:零偏压下的电容为18pF(介电常数137)、介电损耗小于1%,40V偏压下调谐率约为46%,优质因子约为77,能满足微波调谐需要。同时,就有关机理进行了分析。

Yttrium (Y)-doped barium strontium titanate ((Ba0.6Sr0.4)xTiO3 , x<1, Y-BST) films and undoped BST films have been designed in terms of (Ba+Sr)/Ti atomic mol ratio, Y doped concentration and film thickness and prepared on Pt/Ti/SiO 2 /Si wafers by an improved sol-gel method, and the structures and dielectric properties of the films have been studied. X-ray diffraction (XRD) shows that all films exhibit cubic perovskite structures and mainly grow along (110) orientation. With the increase of (Ba+Sr)/Ti ratio (<1) or film thickness, the intensities of perovskite structures and the crystallization of films increase, but with the increase of Y doped concentration (>1% mol ratio), they weaken. 8-layer Y-BST film with (Ba+Sr)/Ti ratio of 0.9 and doped concentration of 2% mol ratio reveals smooth and dense structure with about 30 nm grain size and excellent combination of dielectric properties with capacitance of 18 pF (permittivity of 137) and dielectric loss of less than 0.01 at 0V, and tunability of 46% and figure of merit of 77 at 40 V, meeting the needs of microwave applications. Related mechanisms were also presented.