Temperature-dependent Dielectric Properties of Hybrid MBE-Grown SrTiO₃ Films

SrTiO₃ (STO) is an incipient ferroelectric oxide where the onset of ferroelectric order is suppressed by quantum fluctuations. This has resulted in a giant increase in the dielectric constant from ~300 at room temperature to ~ 20,000 at low temperatures which then remained unchanged at T ≤ 30 K. While this behavior has been routinely observed in bulk STO single crystals, realization of the same in thin films has remained elusive. Low temperature dielectric constant in STO films has been limited to a few hundred or sometimes, to few thousands. Whether the low dielectric constant is due to the defects, or the interface (between film and metal electrodes) has also remained unclear. Using hybrid molecular beam epitaxy (MBE), we present detailed temperature- and frequency-dependent dielectric property measurements of STO films with a dielectric constant exceeding 20,000 in STO films. We discuss an important role of strain, point defects and interface on the measured dielectric constant.