Achievement

Mark Polking elucidates the fundamentals of ferroelectric ordering in nanostructures. Using an NCEM microscope, he examines nanocrystals of GeTe and BaTiO3 in order to map their ferroelectric polarization patterns. He also does nanometer-resolution electron holography experiments with collaborators at Brookhaven National Lab that enable direct imaging of the electric field patterns surrounding these nanocrystals. These experiments provide a complete picture of both the structural and electrostatic manifestations of ferroelectricity. Conflicting reports have been inconclusive until now. His results suggest that local ferroelectric distortions remain primarily linearly aligned in a monodomain state. Analysis of GeTe and BaTiO3 nanocrystals of different shapes indicates that both particle morphology and electrostatic boundary conditions play a significant role in determining the coherence of these local distortions.