Nanosized epitaxial PbTiO3 (PTO) islands with a mono c domain were fabricated via self-assembly on a Nb-SrTiO3 (NSTO) substrate at 160 °C by hydrothermal epitaxy without undergoing the paraelectric to ferroelectric phase transition. The direction of the polarization at the as-fabricated state was observed with an island size up to a lateral area of 104nm2 and thickness of 12 nm (determined by atomic force microscope) using a piezoresponse force microscope. We found a critical size below which the negative polarization is stable at the as-fabricated state and above which the positive polarization is stable. This phenomenon was discussed under two assumptions: that the PTO islands are grown initially with positive polarization during fabrication, and the energy barrier for the transition from the positive polarization state to the negative polarization state is dependent on the ferroelectric island size.

We used hydrothermal epitaxy to fabricate a heteroepitaxial PbTiO3 (PTO) thin film on a Nb-doped (001) cubic SrTiO3 (NSTO) substrate while avoiding the phase transition. By means of transmission electron microscopy and piezoresponse force microscopy analyses, it was confirmed that no a domain formed in the heteroepitaxial PTO film; the film had a single +c-domain structure at an as-synthesized state. From the measurement of the polarization-voltage hysteresis curve, large remanent polarization (2Pr:144μC∕cm2) resulting from the single +c-domain structure and an imprint induced by an asymmetric electrode configuration were observed. It is suggested that the single +c-domain structure was caused by the interface of the PTO film and solution rather than the interface of the PTO film and NSTO electrode under the hydrothermal conditions. This hydrothermally synthesized PTO film is anticipated to be very suitable for high-performance engineering applications.

Heteroepitaxial PbTiO 3 film on an Nb-doped ͑001͒ cubic SrTiO 3 substrate was fabricated by hydrothermal epitaxy at 200°C. Piezoresponse force microscopy and x-ray ⌰ rocking curves confirmed that the film showed a c / a / c / a multi-domain structure even though it did not undergo a cubic paraelectric ͑PE͒ to tetragonal ferroelectric ͑FE͒ phase transition. After heat treatment of this film at 600°C, we observed the ͓110͔ surface band within the a-domain, which was formed through the PE to FE phase transition. We also found that a ͓110͔ surface band existed along the ͑111͒ plane within the a-domain. We predicted that the ͓110͔ surface band would be monoclinic phase due to the interaction of two different variants of a-domains in the presence of a c-domain in the heteroepitaxial PbTiO 3 film.

We observed the retention loss of dot domains ͑36 nm diameter͒ and square domains with sizes of 1 and 25 m 2 that were reversed by applying an electric field at an atomic force microscopy ͑AFM͒ conductive tip on a heteroepitaxial PbTiO 3 thin film with ϩ polarization in the virgin state, which was fabricated via hydrothermal epitaxy below T c . Through theoretical calculations, it was discussed that the retention loss phenomena of a domain reversed by using an AFM tip were derived from the summation of the depolarization field energy and the strain-polarization coupling energy. Since the retention loss of the reversed domain with a straight c / c domain wall by applying a homogeneous electric field did not occur, we suggest that a cylindrical domain, which has a nearly straight c / c domain wall that extends to the bottom electrode on the given thin film, would be free from the retention loss.

We investigated the chemical etching behavior of heteroepitaxial PbTiO3 films on Nb-doped SrTiO3 substrate with mono-+c-domain fabricated by using hydrothermal epitaxy. The as-fabricated films were patterned lithographically into submicron-sized patterns with various lateral sizes using KOH solution and the etching mechanism is suggested. Our study reveals the feasibility of fabricating patterned nanodomains in PbTiO3 films by scanning probe microscopy domain engineering and a chemical etching process. Further, our study shows that an analysis of the distribution and morphology of polarized ferroelectric nanodomains in PbTiO3 is possible through a precise control over the applied bias voltage, pulse width, and time.