Multifrequency electrostatic force microscopy in the repulsive regime
Multifrequency electrostatic force microscopy in the repulsive regime
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DOI：
10.1088/0957-4484/18/6/065502
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发表时间：
2007-02-14
期刊：
影响因子：
3.5
通讯作者：
Stemmer, Andreas
中科院分区：
文献类型：
--
作者：
Stark, Robert W.;Naujoks, Nicola;Stemmer, Andreas
聚合物表面的原子力显微镜通常在排斥调幅模式（轻敲模式）下进行。为了在环境条件下实现静电量的额外测量，在成像过程中使用更高的弯曲本征模式来表征表面的电特性。较高的本征模由尖端和样品之间的小交流偏置电压共振激发。因此，通过这种多频静电力显微镜方法可以同时测量形貌和电势。然而，排斥性尖端-样品接触的强机械非线性可能会引起复杂的动力学。为了最大限度地减少地形信息和静电信息之间可能的串扰，用于静电表征的本征模式的振荡幅度必须保持远小于用于地形成像的本征模式的幅度。此外，还需要验证形貌、机械相位和静电信息等图像数据，并识别信息通道之间可能存在的干扰。通过表征聚合物驻极体上的电荷模式来证明这种谐振多频工作原理的功能。共振多频技术是传统幅度调制模式的扩展，因此可以在大多数原子力显微镜中轻松实现。
Atomic force microscopy on polymer surfaces is commonly carried out in the repulsive amplitude modulation mode ( tapping mode). In order to achieve an additional measurement of electrostatic quantities under ambient conditions a higher flexural eigenmode is used for electrical characterization of the surface during imaging. The higher eigenmode is resonantly excited by a small ac-bias voltage between tip and sample. Thus, topography and electric potential are measured simultaneously by this multifrequency electrostatic force microscopy method. However, the strong mechanical non-linearity of the repulsive tip-sample contact may induce a complex dynamics. To minimize possible cross-talk between topographic and electrostatic information, the oscillation amplitude of the eigenmode used for electrostatic characterization has to be kept much smaller than the amplitude of the eigenmode used for topographic imaging. Additionally, image data such as topography, mechanical phase and electrostatic information needs to be verified and possible interferences between the information channels have to be identified. The capabilities of this resonant multifrequency operation principle are demonstrated by characterizing charge patterns on a polymer electret. The resonant multifrequency technique is an extension to the conventional amplitude modulation mode and thus can be easily implemented in most atomic force microscopes.