Olga S Ovchinnikova oral presentation (PB1-Mon3-1-1)
Multimodal chemical and functional imaging of nanoscale transformations in ferroelectric thin films
Oak Ridge National Laboratory, 1 Bethel Valley Rd, TN 37831-6493 Oak Ridge, United States
Continuing miniaturization of portable electronic and mechanical devices requires development of the novel nanoscale elements. This can be realized using ferroelectric materials, which exhibit a unique set of functional properties. Functionality of ferroelectric materials is defined by the number of physical and chemical phenomena on the nanoscale. While physical aspects of ferroelectric behavior have been studied in details for last several decades, chemical contribution has been almost completely ignored due to the lack of tools for nanoscale chemical investigations. Here, we used a Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) combined with Atomic Force Microscopy (AFM) for correlated investigations of functional and chemical phenomena in ferroelectrics. AFM and in particular Piezo Force Microscopy (PFM) was used to investigate ferroelectric domain structure and induce local ferroelectric switching by applied bias in PbZr0.2Ti0.8O3 (PZT) thin film. Induced chemical changes were further studied by ToF-SIMS in the same vacuum chamber. Correlated imaging revealed a 3-5% change in the spatial concentrations of the base chemical elements (Pb, Ti, Zr) localized within 3.5-nm from the surface. Additionally, the formation of a double layer with higher concentrations on the top and lower concentrations at about 2.5 nm depth was observed shed light on the chemical phenomena associated with ferroelectric properties and are important for Pb. This redistribution of ions has been theoretically predicted to occur due to a screening process that minimizes the depolarization electric filed produced by the boundary charges surfaces. Results of this study for their fundamentals investigations.