Dielectric properties of Co-doped Ba_(0.5)Sr_(0.5)TiO_3 thin films fabricated by pulsed laser deposition

摘要

Undoped and Co-doped Ba_(0.5)Sr_(0.5)TiO_3 thin films have been fabricated by pulsed laser deposition to explore low dielectric loss and high tunability materials for tunable microwave devices. The crystal structure and surface morphology have been characterized by X-ray diffraction and atomic force microscopy. The influence of Co-doping on lattice parameter of Ba_(0.5)Sr_(0.5)TiO_3 materials has been investigated, and the results show that the variation of lattice parameters with Co concentration is different between targets and thin films. The dielectric loss in the Ba_(0.5)Sr_(0.5)TiO_3 thin films with 0.2 and 1 at% Co are 0.064 and 0.039 at frequency of 100 kHz, respectively, which are lower than that of undoped Ba_(0.5)Sr_(0.5)TiO_3 thin films. The tunability of permittivity of the Ba_(0.5)Sr_(0.5)TiO_3 thin films are 34.6% and 18.7% with 0.2 and 1.0 at% Co-doping at applied electric field 200kV/cm.