Local piezoelectric and ferroelectric responses in nanotube-patterned thin films of BaTiO₃synthesized hydrothermally at 200 °C

Piezoresponse atomic-force microscopy (PFM) has been used to characterize the local piezoelectric properties of a novel, nanotube-patterned (“honeycomb”) thin film of BaTiO₃on Ti substrate synthesized hydrothermally at 200 °C. PFM amplitude and phase images, prior to the application of any direct current (dc) field, show ring-shaped piezoelectric regions that correspond to the nanostructure of this film. These results show clearly that the as-synthesized nanotube-patterned BaTiO₃thin film is piezoelectric, with a net spontaneous polarization perpendicular to the film–substrate interface. In addition, polarization switching and hysteresis were observed as a function of applied dc field, confirming that this novel fabrication procedure results in unique configurations of BaTiO₃film that are also ferroelectric.