High-Performance barium titanate capacitors with double layer structure

Abstract

High-performance barium titanate (BaTiO3) capacitors with excellent electrical and dielectric properties have been made by a two step deposition scheme using reactive rf magnetron sputtering. A novel double layer structure has been developed to reduce the pinholes and improve the electrical properties, such as higher dielectric constant, lower dissipation factor, higher breakdown fields and low leakage currents. Films deposited on a cooled substrate are amorphous whereas those deposited on a heated substrate are poly crystalline. Both polycrystalline and amorphous natures are verified by x-ray diffraction and scanning electron microscopy. Amorphous films have a low leakage current, a high breakdown voltage up to 2.5 x 106 V/cm, and a dielectric constant less than 20. Polycrystalline films yield a high dielectric constant of 330. However, these films also have large leakage currents. The capacitors with the two layer structures,i.e. amorphous layer on top of polycrystal layer, have been shown to be much superior to those prepared by either polycrystal or amorphous layer alone for practical applications. The dielectric constant and breakdown voltage of capacitors with a double layer are found to be as high as 220 and 1.2 x 106 V/cm, respectively. The leakage current is reduced to the same order as the amorphous films alone.