Self-assembled PbTiO3 nanoislands of three different shapes with orderly in-plane directions were fabricated on Pt∕SrTiO3 substrates by metalorganic chemical vapor deposition. The shapes of the nanoislands were triangular-shaped (width 50–110nm, height 20–30nm), triangular-prism-shaped (width 50–110nm, length 100–550nm, height 10–30nm) and square-shaped (width 40–130nm, height 4–10nm) on Pt∕SrTiO3(111), (101), and (001), respectively. The PbTiO3 nanoislands were epitaxially grown on the Pt∕SrTiO3 substrates and consisted of {100} and {001} facets irrespective of the orientation of the substrates indicating that structural control of shape and in-plane direction of self-assembled PbTiO3 nanoislands can be achieved through epitaxial relations. The self-assembled PbTiO3 nanoislands with three different shapes were found to be ferroelectric by piezoresponse force microscopy.

The CHNHPbI perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO/porous TiO-perovskite/porous ZrO-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CHNHPbI perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm). Considering the color variation of the CHNHPbI perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CHNHPbI perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

Single-domain BFO thin films are prepared on a SrRuO3-buffered SrTiO3 (STO) (001) substrate by RF planar magnetron sputtering. A domain structure is controlled by vicinal direction of the STO substrate. The BFO thin films on vicinal STO along <110> show single-domain structure without any domain walls. To confirm the influence of epitaxial strain on lattice distortion and ferroelectricity, single-domain BFO thin films with thicknesses ranging from 10–1000 nm are prepared. Synchrotron X-ray diffraction reveals that lattice relaxation and step bunching occur in the thickness range of 50–200 nm. The BFO films with thicknesses over 300 nm are almost free from the influence of the epitaxial strain induced by (001)-oriented substrates. The remanent polarization P r is almost constant at about 60 µC/cm2. However, P r slightly increases in the BFO films with thicknesses less than 200 nm. Even the 100-nm-thick BFO film show fully saturated D–E hysteresis at RT, and the P r is 65 µC/cm2.

We report the fabrication of BiFeO3/BiCrO3(111) artificial superlattices with 1/1 stacking in a layer-by-layer growth mode on atomically flat SrTiO3(111) surfaces. While BiFeO3 and BiCrO3 are antiferromagnets having Fe–O–Fe and Cr–O–Cr bonds, these superlattices contain Fe–O–Cr bonds, in which ferromagnetic interaction is expected. Magnetization measurements at 300 K revealed that the magnetic moment per transition metal ion was 1.7 µB, suggesting ferromagnetic spin order. Ferroelectric behavior at room temperature was confirmed by an analysis using a scanning non-linear dielectric microscope.