High-temperature ferroelectricity in SrTiO₃ crystals

SrTiO$_{3}$ is known to be an incipient ferroelectric. It is thought that ferroelectric stability in SrTiO$_{3}$ is suppressed by a delicate competition with quantum fluctuation and antiferrodistortion. The ferroelectric phase can, however, be stabilized by doping, isotope manipulation and strain engineering etc. Till date ferroelectricity in SrTiO$_{3}$ thin films was observed to exist up to room temperature -- that was when the films were grown on specially engineered substrates using complex growth techniques. It was possible to write and erase ferroelectric domains on the specially engineered films at room temperature. Here, we show remarkably similar ferroelectric behavior in bulk (110) single crystals of SrTiO$_{3}$ with no special engineering well above room temperature using piezoresponse force microscopy. Hysteretic switching of local electric polarization was observed and electrically active domains could be written and erased using lithographic techniques at remarkably high temperatures up to $420K$.