Landau-ginzburg-devonshire theory for domain wall conduction and observation of microwave conduction of domain walls

This chapter concerns DW electrical conduction. It first addresses the phenomenology of charged domain walls in the context of a Landau-Ginzburg-Devonshire (LGD) model for the ferroelectric semiconductor with analysis of the DW conductivity associated with accumulation of charge carriers near domain walls. It is revealed that there exists an interplay between the wall type - head-to-head or tail-to-tail - and conduction type of the semiconductor ferroelectric with a strong dependence of the domain wall conductivity on the wall orientation. The chapter then reviews observations of high-frequency - in the gigahertz frequency range - ac conductivity along the nominally uncharged 180-degree domain walls in a uniaxial Pb(Zr0.2Ti0.8)O₃ epitaxial film. Measurements of the conduction at high frequencies are insensitive to presence of a Schottky barrier and the electrode-ferroelectric interface.