Accurate spring constant calibration for very stiff atomic force microscopy cantilevers.

Area of Science:

• Materials Science
• Nanotechnology
• Metrology

Background:

• Atomic force microscopy (AFM) applications often require precise force quantification between the cantilever tip and sample.
• Accurate force measurement in AFM necessitates knowledge of cantilever stiffness, especially for compliant cantilevers used in low-force applications.
• Existing methods for measuring low stiffness values are insufficient for applications requiring stiff cantilevers (approx. 200 N/m).

Purpose of the Study:

• To present a direct, traceable method for calibrating very stiff AFM cantilevers.
• To establish a reliable method for determining stiffness values beyond the capabilities of existing techniques.
• To reduce uncertainty in stiffness calibration for specialized AFM applications.

Main Methods:

• Utilized an instrumented and calibrated nanoindenter to measure the stiffness of a reference cantilever.
• Employed the calibrated reference cantilever to determine the stiffness of multiple AFM test cantilevers.
• Applied the developed method to calibrate cantilevers with stiffness around 200 N/m.

Main Results:

• Demonstrated a direct and traceable calibration method for stiff AFM cantilevers.
• Achieved significantly smaller measurement uncertainty compared to previously proposed calibration methods.
• Successfully applied the calibrated stiff cantilevers in nanoscale fracture testing of silicon beam specimens.

Conclusions:

• The presented nanoindenter-based method provides a superior approach for calibrating stiff AFM cantilevers.
• This technique enhances the accuracy of force measurements in AFM applications requiring high stiffness cantilevers.
• The method is validated through its successful application in nanoscale fracture mechanics testing.