Professor René Wasserman Award 2012 - Jin Wang

" For a wide scope and original research on the synthesis and characterization of piezoelectric nano-wires of the perovskite family and the theoretical and experimental study of their functionality"

Abstract: Ferroelectric perovskites exhibit superior dielectric, piezoelectric and ferroelectric properties. Architecting ferroelectrics in the small scale holds interest in both application and fundamental research. The thesis focused on central issues in the synthesis, characterization and functionality of ferroelectric perovskite nanowires and on modeling of nite size effects. Monocrystalline nanowires of two important perovskites – Pb(Zr,Ti)O3 and KNbO3, have been synthesized. The growth mechanism of Pb(Zr,Ti)O3 nanowires via the direct hydrothermal method was studied and a fibrous body-centered tetragonal phase (so-called PX phase) with the same composition of the perovskite Pb(Zr,Ti)O3 was found to act as the morphology template. Key structural and functional characteristics of ferroelectric nanowires, such as their lattice distortion, piezoelectric activity, domain structure, switching behavior and phase transitions, were characterized and compared with their bulk and/or thin lm counterparts. At the same time, a theoretical modeling was done to study the inuence of both the short-range surface effects and long-range depolarizing elds in the ferroelectric nanowires and revealed a number of interesting and sometimes unexpected nite size effects. The integration of single ferroelectric nanowires on Si wafer was also demonstrated with KNbO3 nanowire and the performance of the nanowires after the integration was evaluated.