High tunable dielectric properties of Zn and Mg alternately doped Ba0.6Sr0.4TiO3 film varactors

According to the advantages of Zn doped BST (ZBST) and Mg doped BST (MBST) films, Zn and Mg sandwiches alternate doped BST film were designed: ZBST/MBST/ZBST (ZMZ) and MBST/ZBST/MBST (MZM). The film varactors were prepared on the Pt/Ti/SiO2/Si substrate by sol-gel method, their structures and dielectric properties were investigated. X ray diffraction shows that the film is cubic perovskite structure with an average grain size of 19-35 nm, grows along (110) crystal surface and the crystallization is obviously enhanced. SEM shows that ZMZ films are more compact and finer grains than ZBST films. Compared with MBST films, MZM films have little change except that the grains are slightly smaller. When the bias voltage is 20 V and 30 V respectively, the dielectric properties of ZMZ films are similar at low frequency and high frequency. It is worth noting that the ZMZ films exhibited excellent frequency stability, which can meet the needs of tuning electronic devices. Meanwhile, the related mechanisms are also discussed.