报告题目：Defects Mediated Polarization Switching in Ferroelectrics

报 告 人：高鹏， 北大物理学院

报告时间：2015年10月27日10：00

报告地点：理科楼三楼报告厅(C302)

报告摘要：Ferroelectrics have numerous applications including high-density and non-volatile memories, acoustic devices, and sensors. These devices are operated by polarization switching under external excitations, e.g. electrical and mechanical fields. Similar to other first-order phase transitions, the polarization switching is initiated with domain nucleation and followed by domain wall motion, which are dominated by nanoscale defects. Understanding the defects mediated domain dynamics during switching is vital for the device design and optimization.

By using the in situ biasing and indentation TEM techniques, some findings will be presented in this talk. (a) The nucleation of ferroelectric domains occurs at the interfaces between ferroelectrics and electrodes. (b) During switching, the high-energy domain wall relaxes, leading to retention loss in ferroelectric memories. (c) The mobility/immobility of ferroelastic domain walls depends on the specific microstructures. (d) The immobile ferroelastic domains strongly interact with ferroelectric domain wall, resulting in unexpected ‘glassy’ polarization at the charged domain wall. (e) The dislocations act as weak pining centers for 180° domain wall motion, but they can strongly stabilize the ferroelastic domains. Charged point defects can also strongly pin the domain wall via Coulomb interaction.