Domain walls are intrinsic to ferroic materials. Long considered as understood, it is only recently, thanks to atomic-resolution studies using transmission electron microscopy (TEM) or atomic force microscopies (AFM, c-AFM, PFM etc.) that their real structural and electronic complexity has been revealed. Based on this, a new paradigm of ferroic devices is now envisaged where the domain walls, rather than the domains, are the active element. This field has been coined “Domain boundary engineering” or “Domain wall nanoelectronics”.
Photoferroelectrics are materials with both photoelectric and ferroelectric properties. As correlated-electron materials, they are attracting increasing interest because of their high technological potential. Recent reports show that low conversion efficiencies can be counterbalanced by large, above-band gap photo-voltages in complex multiferroic oxides and the fundamental role of the potential difference across domain walls.
More detailed and quantitative knowledge of its structural, electronic and chemical nature is necessary. Fundamental questions on the crystal structure and the electronic structure in the vicinity of the domain wall, as well as their behavior under illumination remain to be elucidated.