What are the best practices for measuring electrical properties of materials using AFM?

1 Choose the right probe

The probe is the key component of the AFM that interacts with the material surface and detects the electrical signals. Therefore, you need to choose a probe that is suitable for the type of electrical property you want to measure, such as conductivity, capacitance, or piezoelectricity. The probe should have a conductive coating, a sharp tip, a high resonance frequency, and a low spring constant. You also need to consider the compatibility of the probe with the material, the environment, and the mode of operation.

2 Set the appropriate parameters

The parameters of the AFM operation, such as the scan speed, the applied voltage, the feedback loop, and the contact force, can affect the quality and resolution of the electrical measurements. You need to set these parameters according to the material properties, the probe characteristics, and the desired outcome. For example, you may want to use a low scan speed and a high applied voltage to enhance the electrical contrast, but avoid damaging the material or the probe. You may also want to adjust the feedback loop and the contact force to maintain a stable and gentle contact between the probe and the material.

3 Calibrate the system

Before you start measuring the electrical properties of the material, you need to calibrate the AFM system to ensure its accuracy and repeatability. You can use a reference material with known electrical properties, such as a metal or a semiconductor, to calibrate the system. You need to measure the electrical response of the reference material under the same conditions as the sample material, and compare it with the expected value. You can then correct any deviation or error in the system by adjusting the gain, the offset, or the sensitivity.

5 Compare and validate the results

Finally, you need to compare and validate the results of your AFM electrical measurements with other methods or references. You can use complementary techniques, such as scanning electron microscopy (SEM), Raman spectroscopy, or electrical impedance spectroscopy (EIS), to verify or supplement your AFM results. You can also compare your results with those reported in the literature or obtained by other researchers. This way, you can confirm the validity and reliability of your AFM measurements, and identify any discrepancies or anomalies that may require further investigation.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?