Effect of Thermal Quench on Ferroelectric Domain Structures in Two-Dimensional Polymers Xia Hong, University of Nebraska-Lincoln, DMR Understanding how the competition between disorder potential and thermal perturbation affects ferroelectricity at the nanoscale and lower dimensions is of fundamental importance and has significant technological impact on optimizing the performance of ferroelectrics-based applications. We have carried out piezo-response force microscopy (PFM) studies of the effect of thermal annealing on ferroelectric domain structures in an intrinsic two-dimensional ferroelectric polymer, poly(vinylidene-fluoride-trifluorethylene). While the static configuration of the domain walls exhibits no appreciable temperature dependence, we observe spontaneous polarization reversal at randomly scattered local sites as the annealing temperature approaches the Curie temperature of ~110 o C (Fig. 1) [1]. This behavior is in sharp contrast to domain nucleation in ferroelectric oxides, which has been attributed to the different competing energy scales involved in domain formation in these two systems. Reference: [1] Z. Xiao, J. Hamblin, S. Poddar, S. Ducharme, P. Paruch, and X. Hong, J. Appl. Phys., in press (2014). Fig. 1. PFM phase response images of (a) a DW written on a 15 ML film at room temperature, and the same DW after thermal quench at (b) 80 °C, (c) 100 °C, and (d) 110 °C. (e) The fractions of the switched areas as a function of the thermal annealing temperature on a 10 monolayer film [1]. Au/SiO 2 PVDF-TrFE RT80 °C 100 °C110 °C 500 nm (b)(a) (c)(d) (e)

Our work on the effect of thermal annealing on ferroelectric domain structures provides new insight in the competing energy scales in low- dimensional ferroic systems, and can facilitate the design of ferroelectric-based flexible nanoelectronics such as non-volatile memories. Three undergraduate students (one female and one McNair Scholar) and one high school graduate have worked on the project. Jennifer Hamblin (Fig. 2) has received the UCARE funding to continue her project on scanning probe studies of ferroelectric domain walls. Based on this project, she co-authored a paper published in Journal of Applied Physics [1] and received the 2014 Physics Department Undergraduate Research Award. The PI and her group members have also outreached to K-12 students and the general public by serving as judges in the Nebraska High School Science Olympiad, presenting in the NCMN Nanoday and Nanocamp, and giving demonstrations and lab tours to the NCPA/ EPSCOR summer science camp (Fig. 3). Effect of Thermal Quench on Ferroelectric Domain Structures in Two-Dimensional Polymers Xia Hong, University of Nebraska-Lincoln, DMR Fig. 2. Jennifer Hamblin, a junior physics student, presented a poster on scanning probe studies of ferroelectric domain walls at the UNL Spring Research Fair. Fig. 3. The PI were giving a demonstration on carbon-based nano-materials to high school students attending the Nebraska Prep Academy Camp.