eddy current显微术中相位信号的距离依赖性
Distance dependence of the phase signal in eddy current microscopy
摘要：
使用磁性尖端的原子力显微镜是研究纳米尺度导电性的一种有前途的工具。通过振荡的磁性尖端，在样品的导电部分中感应出涡电流，其可以在悬臂的相位信号中检测到。然而，相位信号的起源仍然是有争议的，因为理论计算使用的一个appoximation采取的电磁力作用在尖端考虑产生的效果，这是太小了超过两个数量级。为了确定信号的来源，我们使用了特别制备的嵌入在非导电聚碳酸酯基质中的金纳米图案，并测量了相位信号的距离依赖性。我们的数据清楚地表明，相互作用力是长程的，因此，可能是由于磁性尖端和表面导电部分之间的电磁相互作用。由于相互作用的长程特性，可以在远离表面的地方检测到$Δσ=4,5\cdot10^{7} (Ω$ m $)^{-1}$的电导率变化，而不会受到形貌的任何干扰。
英文摘要：
Atomic force microscopy using a magnetic tip is a promising tool for investigating conductivity on the nano-scale. By the oscillating magnetic tip eddy currents are induced in the conducting parts of the sample which can be detected in the phase signal of the cantilever. However, the origin of the phase signal is still controversial because theoretical calculations using a monopole appoximation for taking the electromagnetic forces acting on the tip into account yield an effect which is too small by more than two orders of magnitude. In order to determine the origin of the signal we used especially prepared gold nano patterns embedded in a non-conducting polycarbonate matrix and measured the distance dependence of the phase signal. Our data clearly shows that the interacting forces are long ranged and therefore, are likely due to the electromagnetic interaction between the magnetic tip and the conducting parts of the surface. Due to the long range character of the interaction a change in conductivity of $Δσ=4,5\cdot10^{7} (Ω$m$)^{-1}$ can be detected far away from the surface without any interference from the topography.
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