DIELECTRIC PROPERTIES AT MICROWAVES FREQUENCIES OF (Ni, Ti, La, Mg)-DOPED Ba0.3Sr0.7TiO3 THIN FILMS DEPOSITED ON HIGH-RESISTIVITY SILICON SUBSTRATES

Pure and doped Ba0.3Sr0.7TiO3 thin films are deposited by radio frequency magnetron sputtering using the in-situ process on high-resistivity silicon substrates. Four dopants, La, Ti, Mg, and Ni with different concentrations from 1 to 5 mol%, were studied. The permittivity, dielectric losses, and tunability were determined up to 60 GHz using a coplanar waveguide. The difficulty of simultaneously improving these electrical properties, particularly the loss tangent and tunability, is highlighted. The best improvement was obtained for 5 mol% La for which the losses were in the order of 7.4%, the tunability and the figure of merit were around 29% and 3.9%, respectively, at 60 GHz.