Effect of Gradient of Y Doped Concentration on Structure and Dielectric Properties of BST Films

Six-Layer Yttrium(Y) grade doped Ba0.6Sr0.4TiO3 thin films(1-1.5YBST and 1-2.5YBST) with doping concentrations of 1%/1.1%/1.2%/1.3%/1.4%/1.5% and 1%/1.3%/1.6%/1.9%/2.2%/2.5% have been prepared on Pt/Ti/SiO2/Si substrate by improved sol-gel method.The effect of the gradient of Y doping concentration on the structure and dielectric properties of two films has been researched.X-ray diffraction(XRD) showed that two films mainly grow along(110) orientation and show cubic perovskite structure.Compared to the six-layer 1% Y doped BST film,the diffraction peak intensity and crystallization weaken.However,1-2.5YBST with larger concentration gradient has stronger diffraction intensity and crystallization.Atomic force microscope(AFM) presented that 1-2.5YBST has smoother and denser morphology,smaller surface roughness and grain size.1-1.5YBST and 1-2.5YBST have larger capacitance(dielectric constant),lower dielectric loss and higher tunability.1-2.5YBST shows better combination of dielectric properties with capacitance of 17.45 pF(dielectric constant 127) and dielectric loss(tan) of 0.82% at zero bias,and tunability of 34.6% and figure of merit of 42 at 40 V.