Ferroelectric vortices with triangular lattice symmetry
- Datum: 02.07.2018
- Uhrzeit: 14:00
- Vortragende(r): Hye-Jin Jin
- Department of Physics, Ewha Womans University, Seoul
- Ort: Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale)
- Raum: New Lecture Hall, Building B
New class of vortices in ferroelectric has been obtained by controlling structural formation. Recently, superlattice-arrays were investigated by inducing strain at the interface resulting in ferroelectric vortices. In addition to achievement of superlattice-arrays, the other method to obtain the vortices is formation of artificial lattice in ferroelectrics. Here, we reported an artificial triangular lattice symmetry in tetragonal PbTiO3 thin films by achieving (111) crystal orientations. The contribution of in-plane polarization is strongly enhanced and increase of polarization states is also achieved by rotating the crystallographic orientations. The lattice symmetry was confirmed by using second harmonic generation method and X-ray diffraction patterns. Especially, temporal change of domains was examined by using piezoresponse force microscopy. By applying poling process, domain patterns were controlled and conductivity of domain walls changed. After polarization alignments, dipole frustration occurred charged domain walls inducing rapid decay of poled states. Atomic-scale mapping was obtained by using scanning transmission electron microscopy to find displacement of each atom from original point which shows dipole arrangements. Randomly distributed in-plane polarization states were examined indicating possibility of formation of ferroelectric vortices with external field. Ferroelectric vortices can be obtained by controlling lattice symmetry and our works will give a new agenda for non-volatile memories. Also, I will present recent works for interfacial physics in 2D materials on ferroelectric with triangular lattices.