Molecular Interactions at Ferroelectric Surfaces

Dawn Bonnell

The University of Pennsylvania

Ferroelectric compounds, discovered over 7 decades ago, are organic or inorganic materials that contain electric dipoles intrinsic to the atomic structure of the material. The behavior of these dipoles, and the consequent high dielectric constants of ferroelectric compounds, has been exploited in passive electronic component technologies. Recently, more complex aspects of ferroelectric behavior has been explored for novel optical, electronic, catalytic applications, and even energy harvesting applications. A fundamental issue at the core of ferroelectric behavior pertains to the effects of local fields due to the electric dipoles on atomic and molecular interactions. These are most manifest at surfaces where they influence ferroelectric domain switching, film growth, and local properties.

This talk will present two directions in which molecular interactions at ferroelectric surfaces are investigated and exploited. The first involves Ferroelectric Nanolithography in which domain specific chemical reactivity is controlled to fabricate patterned hybrid nanostructures. In this case the reactions are photo oxidation/reduction producing nanoparticles that are subsequently linked to optically active porphyrins. This process yields interesting opto-electronic patterns, but also raises questions about molecular reactions on ferroelectric domains. The second avenue of research uses controlled UHV studies with in situ poling to examine reactions of water, ethanol, and CO2 on BaTiO3 (100) surfaces, PZT and BTO thin films. In the ideal case of BaTiO3 (100) the atomic structures and thermodynamic stabilities of the surface are determined with a combination of scanning tunneling microscopy, atomic force microscopy and first principles calculations.