Characterization of Structure and Properties of Thin Film Crystals and Ferroelectric BiFeO3 - a Coupled TEM, SPM, and Optical Probe Approach.

Abstract

Correlating advanced microscopy methods including transmission electron microscopy, scanning probe microscopy, and optical spectroscopy on the same materials and even the same specimens allows complimentary measurements to be obtained, revealing new details about structure-property relationships measured on a nanometer scale. Combining measurements not only corroborates the information obtained from any particular method, but also compensates for deficiencies of any single technique. An array of microscopy techniques including high resolution transmission electron microscopy, scanning probe microscopy, and Raman spectroscopy were applied to address scientific and engineering questions concerning the structure and properties of domain patterns in BiFeO3 ferroelectric thin films and to examine novel TiO2(B) thin films suitable for Li-ion battery applications. In BiFeO3, application of these combined techniques allowed a relationship between epitaxial strain and domain width to be established, two cases of strained films with unique domain structures to be identified, transformation of domain structures from all 109° to mixed to all 71° based on differing film thicknesses of 100 and 200 nm to be observed, and to identify growth-induced defects that control domain structure over very long range, 100 nm or more, compared to many studies. In TiO2(B) films, a combination of advanced microscopy and first principals calculations were applied with Raman spectroscopy to produce a definitive reference for further investigation of the crystallinity, structure, composition, and properties of TiO2(B) materials with Raman spectroscopy. Finally to extend these studies of nanostructures and allow direct measurement of electronic and optical properties, the design, development, and construction of proof-of-concept prototypes of specimen rods for in-situ transmission electron microcopy combining electrical probe, scanning tunneling measurements, and optical excitation and spectroscopy is discussed.