Epitaxial crystallization of self-assembled ZnO–NiO nanopillar system

Abstract

We demonstrate a self-assembled ZnO–NiO nanopillar system with a three-dimensional structure as a ZnO-based heterostructure. By designing a three-dimensional epitaxial combination of phase-separated oxide materials and a single-crystal substrate, epitaxial NiO pillars 20–50 nm in diameter and embedded in a ZnO matrix were successfully created on an SrTiO3(111) substrate. The geometry agreed well with the design on the basis of the lattice matching of the film/substrate materials and the thin-film growth modes. Conductive-atomic force microscopy and piezoresponse force microscopy measurements revealed a highly doped semiconducting and piezoelectric ZnO matrix and lightly doped semiconducting and non-piezoelectric NiO pillars.