Paper SS+AS-TuM5
Atomic Structures on BaTiO₃ (001): Reconstructions, Step Edges and Domain Boundaries

Tuesday, October 29, 2013, 9:20 am, Room 201 A

BaTiO₃ is a ferroelectric material that finds applications in a range of traditional and emerging devices. Understanding the surface is prerequisite to controlling interactions during device processing, potential for surface mediated device properties and surface chemical reactions.

Here we present scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) of atomically resolved reconstructions on BaTiO₃ (001) surfaces, √ 5 x √ 5 R26.6^{\circ}$, √ 2 x √2 , $c(4 x 4)$, and √ 13 x √13 R33.7^{\circ}$. We experimentally show the coexistence of two reconstructions √ 2 x √ 2 and $c(4 x 4)$ while DFT calculations indicate that $c(4 x 4)$ is a thermodynamically favorable phase, the √ 2 x √ 2 persists due to a more kinetically favorable path of formation. The structures of the boundaries between the two reconstructions is determined. In the case of the √ 5 x√ 5 R26.6^{\circ}$ surface a comparison of electronic structure determined by STS with theoretical calculations shows that the surface is Ti terminated. In this and other reconstructions Ti-ad atoms create filled and empty states that are imaged in STM. We will briefly discuss a complete BaTiO₃ (001) phase diagram and the influence to Ti adatoms in the choice of step edge direction in the case of the various surface reconstructions mentioned above.