Nanoscale Electric Phenomena at Oxide Surfaces and Interfaces by Scanning Probe Microscopy

Abstract

Scanning Probe Microscopy is used to study and quantify the nanoscale electric phenomena in the two classes of oxide systems, namely transport at electroactive grain boundaries and surface behavior of ferroelectric materials. Scanning Impedance Microscopy is developed to study the capacitance and local C-V characteristic of the interfaces combining the spatial resolution of traditional SPMs with the precision of conventional electrical measurements. SPM of SrTiO3 grain boundaries in conjunction with variable temperature impedance spectroscopy and I-V measurements allowed to find and theoretically justify the effect of field suppression of dielectric constant in the vicinity of the electroactive interfaces in strontium titanate. Similar approaches were used to study ferroelectric properties and ac and dc transport behavior in a number of polycrystalline oxides. In the second part, the effects of local charge density on the chemistry and physics of ferroelectric surfaces are studied. The kinetics and thermodynamics parameters of adsorption are assessed by variable temperature SPM. Piezoresponse force microscopy is used to engineer domain patterns on ferroelectric surfaces. Localized photochemical activity of ferroelectric surfaces is explored as a new tool for metallic nanostructures fabrication.