Dielectric properties of SrTiO3 thin film prepared in a mixture of 18O2 and 16O2 gas

We studied the dielectric properties of SrTiO3 (STO) thin film prepared by pulsed laser deposition in a mixture of 18O2/16O2 gas during deposition. We fabricated an STO capacitor from an YBa2Cu3O7/SrTiO3/YBa2Cu3O7 multilayer structure by using patterning, ion milling, and chemical mechanical planarization. The temperature dependence of ɛr of STO thin film prepared in a 70% 18O2 shows Curie-Weiss behavior down to 2 K without any indication of transition to the ferroelectric state. The frequency dependence of ɛr at 2.2 K shows that ɛr is almost constant in the region between 0.1 kHz and 1 MHz. This differs from the behavior of ɛr of an STO thin film prepared in pure 16O2, which increased as frequency decreased. The result indicates that only small amount of 18O atoms could be incorporated during deposition, and most of the oxygen atoms were transferred from the target.