High-bandwidth multimode self-sensing in bimodal atomic force microscopy.

Area of Science:

• Materials Science
• Nanotechnology
• Physics

Background:

• Standard microelectromechanical systems (MEMS) processes enable microcantilever coating with piezoelectric layers, creating versatile transducers.
• These transducers possess inherent self-sensing capabilities, crucial for advanced microscopy techniques.

Purpose of the Study:

• To demonstrate a single piezoelectric layer's capability for simultaneous multimode excitation and detection in multifrequency atomic force microscopy (MF-AFM).
• To develop a self-sensing scheme that omits traditional piezoelectric stack actuators and optical beam deflection sensors, overcoming their limitations.

Main Methods:

• Utilizing a charge sensor with a 10 MHz bandwidth and dual feedthrough cancellation to isolate resonant modes from piezoelectric capacitance feedthrough.
• Implementing a self-sensing scheme on a microcantilever coated with a piezoelectric layer.

Main Results:

• Achieved a more than two orders of magnitude increase in deflection-to-strain sensitivity on the fifth eigenmode, resulting in a high signal-to-noise ratio.
• Successfully recovered resonant modes obscured by feedthrough, enabling effective multimode excitation and detection.
• Validated the self-sensing scheme through bimodal atomic force microscopy (AFM) imaging of a polymer sample.

Conclusions:

• The proposed self-sensing microcantilever effectively provides feedback signals for topography imaging and phase imaging on higher eigenmodes.
• This approach alleviates limitations of conventional methods, including distorted frequency responses and high instrumentation costs.
• The enhanced sensitivity and signal-to-noise ratio make this self-sensing scheme suitable for advanced MF-AFM applications.