**5. Summary**

Figure 27 shows the evaluated results versus the tested values of Al, Co and Zn samples. It is noted from Figures 20 to 24 that no correlation can be observed between the microwave images and their corresponding geometry images. In other words, the variations of the measured local voltages are not caused by the surface morphology. The main causes of error bars of the evaluated conductivities are as follows. Firstly, the film samples prepared by EB evaporation were not homogenous in the microscopic view, and the distribution of conductivity was

Micro-Nano Mechatronics — New Trends in Material, Measurement, Control, Manufacturing and Their Applications in

**Figure 27.** Evaluated conductivities of the samples in comparison with the tested conductivities of them.

It is believed that the variation margins of measured local voltages (see Figure 25) by the M‐ AFM caused the error bars of the evaluated conductivities. Secondly, the microwave signal for conductivity measurement was very small, which might be affected by the measurement environment. Therefore, the uncertainty of the microwave measurement may contribute to the error bars. It is also noted from Figure 27 that the deviation of evaluated conductivities from the values tested by the Van der Pauw method is 2.03%, 7.24% and 11.6% for the Zn, Co and Al, respectively. One of the causes of this deviation is that the standoff distance variation between different materials may affect the measured voltage, thereby inducing deviation of evaluated conductivity, especially for high‐conductivity materials such as Al. Another cause of the deviation may be the evaluation equation which was derived under the plane wave approximation rather than the much more complicated near field analysis. The quantitative evaluation was performed three times, and the similar results as shown in Figure 25 were obtained. On the other hand, the evaluated resistivities of the five samples can be presented

location‐dependent (local conductivity).

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out as shown in Figure 28.

	- **d.** We have created an M‐AFM‐obtained microwave image using a compact microwave instrument that was optimally synchronized with an AFM scanner. The distinguishing features of M‐AFM are its ability to maintain a constant standoff distance between the probe tip and the sample surface and to measure the microwave signal interacted with the sample. Therein, both the topography and electrical‐property images of the sample can be simultaneously characterized. Therefore, M‐AFM is able to measure, in situ, the distribution of electrical properties on a nanometer scale. As shown in the experimental results, we successfully generated a microwave image of a 200‐nm Au film coating on a glass wafer substrate with a spatial resolution of 120 nm, and, moreover, we measured the voltage difference between these two materials to be 19.2 mV. We believe that the high spatial resolution and simultaneous measurement capability of this M‐AFM system will have important implications to nanotechnology characterization in the immediate future.

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**e.** We also demonstrated a novel evaluation equation and calibration technique for the quantitative measurement of the local conductivity. Based on the analytical and explicit expressions proposed, using two reference samples with known conductivities, the conductivities of any samples can be calculated from the measured voltage. Our results demonstrate that M‐AFM is able to quantitatively measure, in situ, the distribution of electrical properties on the nanometer scale.
