Characterization of novel high ε dielectric and ferroelectric films by scanning probe microscopy (SPM) techniques

Thin films of high epsilon dielectric and ferroelectric materials like barium strontium titanate (BST), lead zirconate titanate (PZT) and strontium bismutate tantalate (SBT) are currently developed for microelectronics applications. The characterization of these films, especially the relationship between their electrical properties and their microstructure, requires techniques with high spatial resolution such as SPM providing both electrical and structural informations at the very same local area. In this study the microstructure of polycrystalline BST, PZT and SET films was imaged by atomic force microscopy (AFM). Electrical properties such as polarization of crystallites and domains as well as tunnelling/leakage currents, were imaged and/or measured by electrostatic force microscopy (EFM) and conductive atomic force microscopy (C-AFM), respectively. In EFM experiments local areas of SET and PZT films could be polarized and reverse polarized. C-AFM studies revealed a strong dependence of the spatial distribution of leakage currents in BST and PZT films on the applied bias voltage. These results demonstrate that SPM techniques operated in a variety of imaging and measuring modes provide a tremendous potential in the elucidation of the microscopic properties of these materials.