Abstract
Piezoresponse force microscopy (PFM) is a powerful technique to characterize ferroelectric thin films by measuring the dynamic electromechanical response. The ferroelectricity is commonly demonstrated by the PFM hysteresis loops and a 180o phase difference of PFM images before and after poling. Such ferroelectric-like behaviors, however, recently are also found in many non-ferroelectrics. Consequently, it is still a challenge to identify intrinsic ferroelectricity in various kinds of thin films. Here, using PFM, we systematically studied the electromechanical responses in ferroelectric thin films with fast (BaTiO3) and slow (PVDF) switch dynamics, and also in the non-ferroelectric (Al2O3) thin films. It is found that both of the ac voltage (Vac) and pulsed dc voltage (Vdc) play an important role in the PFM measurement. When the Vac amplitude is higher than a explicit threshold voltage (Vc), collapse of the PFM hysteresis loops is observed for the films with fast switch dynamics. By measuring PFM hysteresis loops at various Vdc frequencies, an explicit Vc could be found in ferroelectric rather than in non-ferroelectric. The existence of an explicit Vc as well as nonvolatile behavior is proposed as an important approach to unambiguously identify intrinsic ferroelectricity in materials regardless of switch dynamics.
Highlights
Ferroelectric-based devices have received a great attention in the application ranging from nonvolatile memory, piezoelectric energy storage to solar cells etc.[1,2,3] it is still a challenge to probe intrinsic ferroelectricity in nanoscale system
We systematically investigated the Piezoresponse force microscopy (PFM) response of three typical compounds: ferroelectric BTO with fast dynamics, ferroelectric PVDF with slow dynamics and non-ferroelectric Al2O3 thin films
A hysteresis loops can not be observed in BTO and PVDF when the amplitude of Vdc is lower than a coercive voltage
Summary
Ferroelectric-based devices have received a great attention in the application ranging from nonvolatile memory, piezoelectric energy storage to solar cells etc.[1,2,3] it is still a challenge to probe intrinsic ferroelectricity in nanoscale system. In recent years, ferroelectric-like piezoresponse hysteresis loops and PFM images with an 180o phase difference before and after poling are clearly observed in various non-classic ferroelectric materials such as paraferroelectrics, transition metal oxide thin films and Li-ion conductive glass ceramics, etc.[16,17,18,19] which are attributed to a number of alternative mechanisms including charge injection and electrostatic effect,[20,21] electrochemistry,[22] ionic motion,[23] electronic transport,[11] humidity,[24] rather than intrinsic ferroelectricity. It is demonstrated that the intrinsic ferroelectricity can be unambiguously identified by existence of an explicit Vc as well as non-volatile behavior in a broader range of compounds no matter their dynamic process is fast or slow
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
