Orientation dependent microwave dielectric properties of ferroelectric Ba1−xSrxTiO3 thin films

Abstract

The effects of anisotropic dielectric properties of ferroelectric Ba 1Ϫx Sr x TiO 3 ͑BST͒ films on the characteristics of the interdigital ͑IDT͒ capacitors have been studied in microwave regions at room temperature. Ferroelectric BST films with ͑001͒, ͑011͒, and ͑111͒ orientation were epitaxially grown on ͑001͒, ͑011͒, and ͑111͒ MgO substrates, respectively, by the pulsed laser deposition method. The microwave properties of orientation engineered BST films were investigated using interdigital capacitors. The calculated dielectric constant tunability with 40 V dc bias variation and the calculated dielectric quality factor values for IDT capacitors based on ͑001͒, ͑011͒, and ͑111͒ oriented BST films at 9 GHz with no dc bias were about 47%, 55%, 43%, and 12, 14, 21, respectively.

The model of electric field dependent dielectric properties for porous ceramics

“…This may be attributed to the fact that our model does not consider the effect of the change of grain size, a little preferred orientation, and distribution of the pores, whereas there will be a departure as the pore increases. 14,17,18 Further work will be done to improve the model in the future.…”

Optical and electro-optic anisotropy of epitaxial Ba0.7Sr0.3TiO3 thin films

“…The polarization changes could originate from: ͑1͒ the magnitude variation of the relative displacement of the Ti 4+ with respect to O 2− , ͑2͒ the change of domain growth mechanism, and ͑3͒ the lattice distortion caused by the stain in perovskite structure. 5,10 Other factors, such as dielectric permittivity, may also be responsible for the orientation dependence of E-O effect in our tetragonal-distorted BST thin films. 22 Further investigation needs to be conducted in order to clarify the underlying physics of the E-O anisotropy in BST films.…”

“…The growth conditions used in this work have been optimized and agreed well with reported data by other group. 10 The crystal structures of the Ba 0.7 Sr 0.3 TiO 3 thin films were examined using an x-ray diffractometer ͑Bruker D8 Discover͒ equipped with Cu K␣ radiation. No secondary orientations and phases are detected from the / 2 scans ͑fig-ures not shown here͒, indicating the BST films are oriented along the particular normal of the substrates with a pure perovskite phase.…”

Effects of substrates on the structure and dielectric properties of Ba(Sn0.15Ti0.85)O3 thin films

“…This difference in dielectric properties in these four kinds of BTS films may be attributed due to different grain size and change in the direction and magnitude of electric polarization in orientation engineered BTS films. These polarization changes come from the magnitude variation of the relative displacement of the Ti ion with respect to the O ion, the domain growth mechanism change, and the strain and stress changes in perovskite BTS film [17]. The room temperature dielectric constant of the BTS thin films deposited on annealed LNO/ Pt(1 1 1)/Ti/SiO 2 /Si substrates was relatively higher than that of the thin films deposited on Pt(1 1 1)/Ti/SiO 2 /Si and unannealed LNO/Pt(1 1 1)/Ti/SiO 2 /Si substrates.…”