Microstructural studies and electrical properties of Mg-doped SrTiO3 thin films

The structure–property relations of Mg-doped SrTiO3 (ST) sol–gel thin films deposited on Pt/TiO2/SiO2/Si substrates have been investigated in order to determine the effect that Mg dopants have on the dielectric properties of SrTiO3. It has been predicted that Mg-doped SrTiO3 should exhibit a dielectric anomaly similar to that observed recently in Bi doped SrTiO3 but, to date, no polar state has been reported. It has been suggested that this may relate to the low solubility of Mg on the A-site in bulk ceramics (<0.05 at.%). However, for Sr1−xMgxTiO3 (SMT) (x ⩽ 0.30) films annealed at 750 °C, all Mg ions were accommodated in the perovskite lattice and for SMT films annealed at 900 °C, the solubility limit of Mg was x = 0.10, above which a Mg-rich ilmenite second phase was observed. Irrespective of the higher solid solubility limit of Mg in the ST lattice for sol–gel ST films compared to equivalent ceramics, no ferroelectric or relaxor phase transition was observed, refuting previous predictions for this dopant.