Formation and local conduction of nanopits in BiFeO3 epitaxial films

Abstract

The creation and manipulation of one-dimensional conducting channels, V-shaped nanopits, in otherwise insulating BiFeO₃ epilayers are reported. The formation and thickness-dependent evolution of nanopits have a close correlation with the relaxation of shear strain that stems from the crystal symmetry mismatch between BiFeO₃ and the substrate. The local conduction at the nanopits exhibits a rectification behavior, and is governed by interface-regulated Poole–Frenkel emission. The accumulation of oxygen vacancies near the nanopits not only modifies the interface barrier height, but also delivers donor states in the vicinity of the conduction band edge, and therefore leads to locally enhanced nanopit conductance. Our findings provide a new insight into the interplay between defects and epitaxial strain, and open up a possible avenue for oxide nanoelectronics.