Energy transfer between eigenmodes in multimodal atomic force microscopy.

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Atomic Force Microscopy (AFM) traditionally uses a single cantilever vibration mode.
• Monomodal AFM provides limited information on complex sample properties.
• Multimodal AFM offers potential for enhanced sensitivity and contrast.

Purpose of the Study:

• To investigate tetramodal and pentamodal AFM experimentally and computationally.
• To explore the generation of additional observables from multiple excited eigenmodes.
• To demonstrate enhanced contrast and new insights into sample properties using multimodal AFM.

Main Methods:

• Simultaneous external excitation of the first four (tetramodal) or five (pentamodal) flexural eigenmodes of an AFM cantilever.
• Acquisition of additional amplitude and phase signals beyond monomodal methods.
• Conversion of observables into dissipation and virial expressions for enhanced contrast analysis.

Main Results:

• Tetramodal and pentamodal AFM generate six to eight additional observables.
• These observables yield three to four dissipation and virial expressions, revealing hidden contrast.
• Significant energy transfer occurs between eigenmodes, with individual modes showing positive or negative dissipated power.
• Total dissipated power remains positive despite inter-eigenmode energy transfer.

Conclusions:

• Multimodal AFM provides enhanced contrast by utilizing additional observables.
• Individual eigenmode contrast in multifrequency AFM should not be analyzed in isolation.
• Different eigenfrequencies in multimodal AFM can probe sample properties with distinct relaxation times.