The Mg influence on the properties of SrTiO3 thin films

The solid solubility limit of atomic substitutions is expected to be dependent on the size scale (bulk ceramics and films) of materials and on processing. In this work, the incorporation of Mg on A and B sites of SrTiO3 (ST) thin films prepared by sol–gel on Pt/TiO2/SiO2/Si substrates is investigated. The solid solubility of Mg evaluated by XRD analysis, is limited to x ≤ 30% for A-site occupancy (SMT) and to y ≤ 40% for B-site occupancy (STM). It is observed that the lattice constant decreases for SMT and increases for STM films with increasing concentration of Mg. The dielectric constant and loss tangent at room temperature are reduced for SMT and STM films. The losses of Mg-doped ST films are lower than 0.05. The tunability of doped ST films is about 6% at 100 kV/cm2 and room temperature and its dependence on the Mg contents varies with dopant lattice site occupancy. The obtained behavior is compared with identical bulk ceramic compositions and discussed. The higher degree of chemical homogeneity attained in solution and the strains induced in the films are controlling parameters of the solid solubility of Mg on ST films.