Noncontact method for calibration of lateral forces in scanning force microscopy

Area of Science:

• Atomic Force Microscopy
• Nanotechnology
• Surface Science

Background:

• Lateral force microscopy (LFM) requires accurate calibration for reliable measurements.
• Existing calibration methods can be time-consuming and may damage the cantilever tip.
• In situ calibration in various environments, including liquids, is challenging.

Purpose of the Study:

• To develop a noncontact calibration procedure for lateral force microscopy.
• To enable accurate calibration of both normal and lateral forces.
• To provide a method suitable for in situ calibration in air and liquids.

Main Methods:

• Utilizes the thermal noise spectrum of the cantilever.
• Employs Sader's method to determine the cantilever's spring constant from its thermal noise spectrum.
• Requires only the cantilever's plan view dimensions, measurable via optical microscopy.
• A two-step procedure for calibration in liquids involves capturing thermal spectra in air and the liquid.

Main Results:

• The noncontact calibration procedure accurately determines force sensitivity.
• Results from the thermal noise technique show good agreement with traditional wedge calibration.
• The method successfully calibrates normal and lateral forces without surface contact.

Conclusions:

• This noncontact calibration procedure offers a robust and non-destructive method for LFM.
• The technique is effective for in situ calibration in diverse environments, including viscous fluids.
• Eliminates the risk of tip damage or contamination during the calibration process.