NJIT Physics Dept - MtSE Joint Seminar

September 11th, Monday

Polarization Induced Conduction and Screening

Prof. Yukio Watanabe

Kyushu University, Japan

(Condensed Matter/Materials Physics, Host: Gordon Thomas)

Time: 11:45am-12:45pm with 11:30am tea time

Room: ECE 202

Ferroelectrics are materials having electrically reversible spontaneous polarization. This talk presents their properties in view of electron dynamics, which has been lacking conventionally. Conduction at SrTiO₃/LaAlO₃ is intensively studied. Two years before this, not only conduction but its switching of BaTiO₃ surface was reported by us [1]. This verified also conduction at domain boundaries and ferroelectric interfaces. Both conductances are too small for electronics, but that of BaTiO₃ are of fundamental importance for the bases of ferroelectric such as prevailing vortex domain theories and ferroelectric FET. Our experiments find conduction of both +P surface and -P surface. Our calculations show the location of each conduction is titanium of one unit cell deeper than top surface and the outermost oxygen, respectively. This screening explains the absence of natural vortex domains on free surface as well as properties of nano-ferroelectrics such as compulsory nano-domain. Using nm-scale and macroscopic probes, we will clarify natural domains of atomically flat fully oxygenated surface of stoichiometric BaTiO₃ single crystal in UHV, air, and acid, which will be explained by density functional and Ginzburg-Landau calculations.

[1] Watanabe et al., Phys. Rev. Lett. 86 (2001).