Effects of Ambient Gas on Dielectric Constant of Sputtered SrTiO3 Epitaxial Thin Films

Epitaxial strontium titanate (SrTiO3) thin films were fabricated on Pt/MgO substrates by rf magnetron sputtering in O2 (100 sccm) and Ar/O2 (40/10 sccm) ambients. Films prepared in an O2 ambient exhibit an anomalous dielectric constant (ε r=450), larger than that of the bulk single crystal. An investigation was carried out on the relationship between stoichiometry, deposition rate, and peening effects and this anomalous dielectric constant. We conclude that the anomalous dielectric constant is attributable to the lattice elongation along the c-axis caused due to the peening effect of O species.