Improving dielectric loss and enhancing figure of merit of Ba0.5Sr0.5Ti0.95Mg0.05O3 thin films doped by aluminum

The different Al contents effects of Ba0.5Sr0.5Ti0.95Mg0.05O3 (BSTM) thin films grown on Pt/TiN/SiO2/Si substrates in the crystallographic structure, surface morphology, dielectric constant, loss tangent, leakage current, and figure of merit were investigated. The BSTM films properties are studied as a function of Al content and have remarkable improvements including dielectric loss, leakage current, and figure of merit (FOM) as well as films grain sizes. With increasing Al content, the dielectric constant (k), tunability (T), loss tangent (tanδ), and leakage current density (JL) decrease while the FOM, defined as T/tanδ, and breakdown strength increases. The maximum dielectric constant at zero bias, tunability, dielectric loss, FOM, and leakage current density of 1mol% Al-doped BSTM films at 280kVcm−1 are 248, 40%, 0.0093, 43, and 3.76×10−7Acm−2, however, the same measured conditions of undoped BSTM films are 341, 54%, 0.0265, 20, and 1.19×10−6Acm−2, respectively. The dc resistivity increases from 2.33×1011Ωcm of the BSTM film to 6.08×1012Ωcm of the 5mol% Al-doped BSTM film at 280kVcm−1. In addition, the tolerance factor (t) of Al-doped BSTM perovskite thin films is 0.97 as compared to 0.87 of the undoped BSTM thin films. The increasing of tolerance factor value indicates that the specimens with Al-doped BSTM films are more stable than undoped specimens.