1x1.5  m 2 Capacitor Introduction An experimental approach for quantitative measurements of the polarization reversal mechanism in PZT thin film ferroelectric capacitors based on piezoresponse force microscopy (PFM) in conjunction with a pulse switching system is presented. Instant domain configurations developing in the 1x1.5  m 2, 3x3  m 2 and 5x5  m 2 capacitors at different stages of the polarization reversal process have been detected by PFM. Along with the domain structure imaging the switching current signal is measured. Integration of the switching current signal provides information on the time dependence of the switching charge that is compared with the domain switching dynamics measured by PFM. It is shown that the polarization reversal process is characterized by two distinctive stages: the fast one which proceeds mainly via nucleation mechanism and the slow one where the predominant mechanism is lateral domain growth. The fraction of the capacitor switched via the different mechanisms is field dependent with the contribution of the nucleation mechanism increasing with the field strength. From comparison of the domain dynamics and switching current it is shown that the slow switching stage is not detected by the current measurements. This effect is further manifested in the capacitor size effect on switching behavior - with the decrease in the capacitor size the contribution of the nucleation mechanism is diminished due to the reduced square/perimeter ratio. These findings dictate the necessity of developing a new approach for describing the switching behavior in the thin film capacitors. Comparison of PFM and Switching Current Modeling Experimental data PFM of Instant Domain Configurations PFM measurement reveals more complete switching in compare with transient measurement PFM of Instant Domain Configurations 3x3  m 2 Capacitor 20ns,1.8V50ns,1.8V 100ns,1.8V500ns,1.8V 5  s,1.8V 500  s,1.8V Comparison of PFM and Switching Current.PFM measurement reveals more complete switching in compare with transient measurement 5x5  m 2 Capacitor PFM of Instant Domain Configurations 10ns,1.8V20ns,1.8V25ns,1.8V30ns,1.8V50ns,1.8V100ns,1.8V Wall Motion 23ns,1.8V25ns,1.8V28ns,1.8V33ns,1.8V40ns,1.8V60ns,1.8V The scaling effect on switching behavior is manifested by a decrease in the contribution of the nucleation mechanism to polarization reversal: switching proceeds mainly via domain lateral growth Quantitative Studies of Domain Switching Dynamics in Thin Film Ferroelectric Capacitors Dong Wu, Brian Rodriguez 1, Alexei Gruverman North Carolina State University, Raleigh, NC, USA 1 Current affiliation: Oak Ridge National Laboratory, Oak Ridge, TN, USA NC STATE UNIVERSITY Modeling Experimental data Step-by-Step PFM imaging reveals that different mechanisms contribute to the switching process: nucleation and wall motion There are more nuclei forming during switching in 3x3 µm 2 capacitors than in 1x1.5 µm 2 capacitors. Nucleation It is found that the capacitor switching behavior is spatially inhomogeneous – capacitor regions along the electrode edge mainly switch via the lateral domain wall motion while the switching in the central regions is dominated by nucleation. Nucleation KAI model doesn’t provide adequate description for the high-field switching in small capacitors. NLS model provides better approximation for the switching in small capacitors. For the increased capacitor size, the KAI model fits the high-field switching data better, but still have some differences. NLS model fits the data well. For large capacitor size both models fit the high-field switching data well. 1. SbS PFM imaging reveals more complete information on the switching mechanism in ferroelectric capacitors compared to the switching current measurements. 2. Switching process is spatially inhomogeneous: perimeter regions tend to switch slower than the inner regions of the capacitors (presumably due to the increased local threshold field caused by the processing damage) 3. Capacitor scaling effect on switching behavior is manifested by the change in the increased role of lateral domain growth in smaller capacitors. Conclusion Wall Motion The weak current signal of small capacitor is comparable to the noise level so that most of the switching information will be undetected. But step-by-Step PFM images reveal much more detail on switching process. Oscilloscope (Observe the Switching current) Pulses train for transient current measurement Experimental Setup Pulses train for PFM measurement capacitors Function Generator Piezoresponse Topography 1x1.5  m 2 Capacitor 3x3  m 2 Capacitor 5x5  m 2 Capacitor