Ferroelectric Domain Wall p-n Junctions.

Abstract

We have used high-voltage Kelvin probe force microscopy to map the spatial distribution of electrical potential, dropped along curved current-carrying conducting domain walls, in x-cut single-crystal ferroelectric lithium niobate thin films. We find that <i>in-operando</i> potential profiles and extracted electric fields, associated with <i>p-n</i> junctions contained within the walls, can be fully rationalized through expected variations in wall resistivity alone. There is no need to invoke additional physics (carrier depletion zones and space-charge fields) normally associated with extrinsically doped semiconductor <i>p-n</i> junctions. Indeed, we argue that this should not even be expected, as inherent Fermi level differences between <i>p</i> and <i>n</i> regions, at the core of conventional <i>p-n</i> junction behavior, cannot occur in domain walls that are surrounded by a common matrix. This is important for domain-wall nanoelectronics, as such in-wall junctions will neither act as diodes nor facilitate transistors in the same way as extrinsic semiconducting systems do.