We demonstrated that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature ( T c ) in ferroelectric ultrathin films and superlattices. We showed that one-unit-cell-thick BaTiO 3 layers in BaTiO 3 /SrTiO 3 superlattices are not only ferroelectric (with T c as high as 250 kelvin) but also polarize the quantum paraelectric SrTiO 3 layers adjacent to them. T c was tuned by ∼500 kelvin by varying the thicknesses of the BaTiO 3 and SrTiO 3 layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.

Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO(3) template layer with superior piezoelectric coefficients (e(31,f) = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.

Three‐dimensional nanoarchitectures (see Figure) are formed by the oriented aggregation of CuO nanoparticles. One‐dimensional orientation in the early stages of aggregation (in the [001] plane) of CuO nanoparticles is followed by formation of single‐crystalline nanostructures consisting of hundreds of oriented nanoparticles.

A general approach to modifying preformed dendrimerentrapped Au nanoparticles with different functionalities is proved to improve their biocompatibility.

Dislocation arrays and dislocation half-loops in BaTiO 3 thin films were characterized using transmission electron microscopy ͑TEM͒. BaTiO 3 films with thicknesses ranging from 2 to 20 nm were grown on ͑100͒ SrTiO 3 by reactive molecular beam epitaxy ͑MBE͒. The critical thickness for dislocations to occur in this system was found to lie between 2 and 4 nm. The misfit dislocations are mainly ͗100͘ type. The average spacing between the dislocations in the array becomes smaller when the film is thicker, which indicates gradual relaxation of mismatch strain with increasing film thickness.