In-Plane Ferroelectricity in Strontium Titanate Thin Films

摘要

The results of structural and electrical characterizations of SrTiO_3 thin films deposited onto LaAlO_3 substrates by pulsed laser deposition technique are presented. The appearance of the ferroelectric phase in these films has been experimentally documented, the transition temperature being in the range of 90-120K. The hysteresis loops have been monitored in a wide temperature range by using thin film planar capacitors, the driving field being predominantly in the plane of the film. The switching properties of the films has been studied at low temperatures (～25 K) and well saturated loops have been observed with relatively low coercive field (<6kV/cm for 10μm gap). The presence of the imprint phenomenon has been also found at low temperatures. The microstructure of the investigated SrTiO_3 thin films has been studied by using a high resolution transmission electron microscope (TEM). It has been found that the annealed and as-deposited thin films, being of the same composition, have quite different microstructures. The difference observed in the polarization response of the films is related to that in their microstructure.