Ferroelectric domain imaging of $Pb(Zr,Ti)O_3$ thin films using atomic force microscope

Abstract

Ferroelectric domain imaging using atomic force microscope (AFM) has attracted much attention due to its capability of probing in-situ domain structure down to nanometer scale in a non-destructive way. The macroscopic properties were successfully explained in terms of domain structure and dynamics directly observed by AFM. However, the exact reading mechanism of domain imaging by AFM has not been clarified and thus the interpretation of domain images remained unclear. Therefore, the reading mechanism of domain imaging using AFM has been investigated and disclosed by model experiments on silicon oxide and $Pb(Zr,Ti)O_3$ (PZT) thin films. Cantilever-sample interaction was found to take an important role in domain imaging. This interaction adds to the tip-sample piezoelectric interaction thereby obscuring the obtained tip vibration signal. To minimize such an interaction, it was proposed to either put a large area top electrode in between the tip and the sample or use a high aspect ratio tip. These methods have proved to be successful in view that the cantilever-sample interaction was hardly detected and only tip-sample interaction was observed. The polarization switching and fatigue phenomena in PZT thin films were studied using a large area top electrode in between the tip and the sample. The macroscopic electrical properties were simultaneously acquired and compared with the corresponding domain structure. Based on the analysis, the polarization switching occurs by forward domain growth being rate-limiting mechanism. Polarization suppression occurs region by region and shows either preferential direction of top to bottom or no preferential direction for frozen domains. Finally, the formation and characteristics of micron to sub-micron size domains aligned by AFM tip in PZT thin films were studied. The retention characteristics of the domains were analyzed. The retention time shows a linear dependence upon the size of the aligned domains. This dependence was exp...