Leakage current characteristics of polycrystalline BiFeO3 thin films affected by thickness-dependent domain wall currents

Abstract

Polycrystalline BiFeO3 (BFO) thin films with a mixed crystallinity of c-oriented crystallinity and a-oriented crystallinity were deposited on a (200) Pt/TiO2/SiO2/Si substrate to have a thickness of 50, 100, and 150 nm. The ferroelectric domains observed with vertical piezoresponse force microscope (VPFM) and lateral PFM (LPFM) showed a mixed domain structure of c-domains and a-domains, and the ratio of a-domains increased as the thickness increased. The domain wall currents at the a-domains and c-domain boundaries of the BFO thin films were measured by conduction atomic force microscopy (CAFM) experiments and they were larger than those at the c-domains boundaries. In particular, the leakage currents, ferroelectric polarizations, and piezoelectric coefficients of the BFO thin films according to their thickness were significantly affected by the formation of the a-domains.