Simultaneously measured signals in scanning probe microscopy with a needle sensor: frequency shift and tunneling...

Area of Science:

• Surface Science
• Scanning Probe Microscopy
• Nanotechnology

Background:

• Accurate surface characterization is crucial for understanding material properties.
• Noncontact scanning methods minimize sample damage during imaging.
• Integrating multiple imaging modalities enhances data richness.

Purpose of the Study:

• To develop a combined noncontact scanning force microscopy and tunneling current imaging technique.
• To investigate the simultaneous measurement of frequency shift and tunneling current.
• To analyze the behavior of feedback-controlled and free signals for surface topography determination.

Main Methods:

• Utilized a 1 MHz quartz needle sensor for combined imaging.
• Integrated low-frequency tunneling current with high-frequency quartz resonator signals.
• Employed simultaneous detection of frequency shift and tunneling current.
• Implemented feedback control using one of the detected signals.

Main Results:

• Achieved simultaneous noncontact scanning force microscopy and tunneling current imaging of a platinum(111) surface.
• Demonstrated full electrical operation of the quartz needle sensor.
• Observed proportional-integral controller error-like behavior in the free signal, related to the topography's time derivative.
• Proposed a method to determine mechanical oscillation amplitude using tunneling current and tip-sample work function.

Conclusions:

• The combined technique provides a powerful tool for surface analysis.
• The observed signal behavior offers insights into the dynamics of scanning probe microscopy.
• The proposed procedure aids in accurate measurement of surface properties and tip-sample interactions.