Abstract
Atomic force microscopy (AFM) is central to investigating the piezoelectric potentials of one-dimensional nanomaterials. The AFM probe is used to deflect individual piezoelectric nanorods and to measure the resultant current. However, the torsion data of AFM probes have not been exploited to elucidate the relationship between the applied mechanical force and resultant current. In this study, the effect of the size of ZnO nanorods on the efficiency of conversion of the applied mechanical force into current was investigated by simultaneously acquiring the conductive AFM and lateral force microscopy signals. The conversion efficiency was calculated based on linear regression analysis of the scatter plot of the data. This method is suitable for determining the conversion efficiencies of all types of freestanding piezoelectric nanomaterials grown under different conditions. A pixel-wise comparison of the current and lateral force images elucidated the mechanism of current generation from dense arrays of ZnO nanorods. The current signals generated from the ZnO nanorods by the AFM probe originated from the piezoelectric and triboelectric effects. The current signals contributed by the triboelectric effect were alleviated by using an AFM probe with a smaller spring constant and reducing the normal force.
Highlights
The piezoelectric effect of ZnO nanorods was first reported by Wang and Song in 20061
Whereas the lateral force microscopy (LFM) signal was transmitted through the position-sensitive photodetector (PSPD), the C-Atomic force microscopy (AFM) signal was obtained via the current amplifier (Fig. 3)
We performed comprehensive analysis of the piezoelectric and triboelectric effects generated in ZnO nanorods using an AFM probe
Summary
The piezoelectric effect of ZnO nanorods was first reported by Wang and Song in 20061. The correlation between the topography signal and conductive atomic force microscopy (C-AFM)[7,8] signal was analyzed to elucidate the underlying mechanism responsible for the generation of a piezoelectric potential in ZnO nanorods and to detect the current signal via the AFM tip. The C-AFM and LFM signals can be readily acquired simultaneously during AFM operation in contact mode In this work, this novel experimental method was used to study the effect of the ZnO nanorod size on the efficiency of conversion of the mechanical force to which they are subjected into current via the piezoelectric and triboelectric effects. The contribution of the triboelectric effect is quite large when an AFM probe with a large spring constant is used with a large normal force
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