抄録
Barium Strontium Titanate (BST) thin film films have great potential for use in microwave devices including decoupling capacitors and varactors. For these applications a high capacitance density or voltage tunability (change in permittivity with voltage), low leakage current density, and low dielectric loss and are often simultaneously required. However, present material synthesis approaches have succeeded primarily in optimizing one particular electrical property without enhancements in the others. This study investigates the use of dopant engineering to achieve large and simultaneous improvements in permittivity, voltage tunability, and lower leakage current densities in BST-based thin film capacitors being developed for GHz decoupling applications. We demonstrate that by Y dopant incorporation into BST thin films it possible to simultaneously achieve 70% higher permittivity and voltage tunability of permittivity along with more than ten-order-of magnitude lower leakage current density as compared to nominally undoped films using the same deposition condition. We will show that the remarkably enhanced permittivity for Y doped BST films is consistent with a reduction in biaxial elastic film strain and discuss the possible mechanisms for the lower leakage current based on the defect chemistry of transition metal amphoteric dopants in ABO3 perovskite-structure titanate materials.
