Effect of K-doping on the dielectric and tunable properties of Ba 0.6Sr 0.4TiO 3 thin films prepared by RF magnetron sputtering

Abstract

Ba 0.6Sr 0.4TiO 3 (BST) thin films doped by K (0, 5, 10 and 12.5 mol%) (BSTK) were deposited by radio frequency (RF) magnetron sputtering on Pt/Ti/SiO 2/Si substrates. Atomic force microscopy and X-ray diffraction analysis were used to investigate the structure and morphology of the BST thin films. The dielectric measurements were conducted on metal–insulator–metal capacitors at the frequencies from 1 kHz to 1 MHz. It was found that the K concentration in BST thin films has a strong influence on the material properties including surface morphology, dielectric, and tunable properties. The surface root-mean-square roughness of the BSTK films decreased when 5 mol% K was doped and increased with increasing content of K hereafter. The dielectric constant, dielectric loss and tunability increased when K was doped in the BSTK thin films. The (Ba 0.6Sr 0.4) 95%K 5%TiO 3 thin film exhibited the highest tunability of dielectric constant of about 62.3% and a figure of merit of 26.1 at a maximum applied bias field at 1 MHz.