Dielectric properties of Ti-deficient SrTiO_3-δ thin films

Abstract
Ti-deficient SrTi_xO_3-δ thin films were prepared by high frequency magnetron sputtering. Electric transport and dielectric characterization was carried out by using plate-like capacitors with YBa₂Cu₃O_7-δ as electrode material. Samples with x = 0.988, 0.98 and 0.89 were measured in the frequency and temperature range between 100 Hz and 100 kHz and 4.2 K and 300 K, respectively. The transport properties of the films were dominated by variable range hopping via localized states. With decreasing x the density of localized states increases nearly linearly indicating that the Ti-deficiency is primarily compensated by the formation of point defects. For low defect concentration, x > 0.89, the dielectric constant is enhanced significantly by the defect formation whereas, for x ≤ 0.89, a very strong decrease of the polarization occurs accompanied by a drastic increase of the dielectric loss. tan δ.