The integration of ferroic oxide thin films into advanced flexible electronics will bring multifunctionality beyond organic and metallic materials. However, it is challenging to achieve high flexibility in single-crystalline ferroic oxides that is considerable to organic or metallic materials. Here, we demonstrate the superior flexibility of freestanding single-crystalline BiFeO3 membranes, which are typical multiferroic materials with multifunctionality. They can endure cyclic 180° folding and have good recoverability, with the maximum bending strain up to 5.42% during in situ bending under scanning electron microscopy, far beyond their bulk counterparts. Such superior elasticity mainly originates from reversible rhombohedral-tetragonal phase transition, as revealed by phase-field simulations. This study suggests a general fundamental mechanism for a variety of ferroic oxides to achieve high flexibility and to work as smart materials in flexible electronics.

Previous studies suggest that myopia in parents may influence the genesis of myopia in their offspring. In this study, we surveyed 2888 children of Chinese descent in China and Hong Kong to determine the relationship between the refractive state of parents and their children. The age range of the children was 7-17 years. Refraction was measured using a Canon R-22 objective infrared autorefractor and a survey on family history of ametropia was conducted using a questionnaire. We found that children with myopic parents are more likely to be myopic.

In this work, we present a nonlinear silicon nitride waveguide. These waveguide are fabricated by readily available PECVD, conventional contact UV-lithography and high-temperature annealing techniques, thus dramatically reducing the processing complexity and cost. By patterning the waveguide structures firstly and then carrying out a high-temperature annealing process, not only sufficient waveguide thickness can be achieved, which gives more freedom to waveguide dispersion control, but also the material absorption loss in the waveguides be greatly reduced. The linear optical loss of the fabricated waveguide with a cross-section of 2.0 × 0.58 µm was measured to be as low as 0.58 dB/cm. The same loss level is demonstrated over a broad wavelength range from 1500 nm to 1630 nm. Moreover, the nonlinear refractive index of the waveguide was determined to be ~6.94 × 10 m/W, indicating that comparable nonlinear performance with their LPCVD counterparts is expected. These silicon nitride waveguides based on a PECVD deposition platform can be useful for the development of more complicated on-chip nonlinear optical devices or circuits.

No abstract

No abstract