Subsurface phase imaging of tapping-mode atomic force microscopy at phase resonance.

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Tapping-mode atomic force microscopy (TM-AFM) phase images reveal sample properties like Young's modulus and adhesion.
• Standard TM-AFM uses frequencies near the first resonance peak, offering high amplitude but low phase sensitivity.
• Low phase sensitivity limits detailed subsurface morphology analysis.

Purpose of the Study:

• To improve image resolution in TM-AFM by optimizing probe driving frequency.
• To investigate the potential of phase resonance peak driving for enhanced subsurface imaging.
• To analyze the impact of setpoint variations on subsurface imaging resolution and depth sensitivity.

Main Methods:

• Utilized the frequency at the probe phase resonance peak for driving probe vibration in TM-AFM.
• Performed phase imaging on uniform photoresist samples of varying thicknesses.
• Systematically altered probe setpoint values while keeping other scanning parameters constant.

Main Results:

• Driving TM-AFM at the phase resonance peak significantly improved image resolution.
• Decreasing the setpoint value reduced horizontal resolution but initially increased depth sensitivity.
• Optimized phase resonance imaging enabled better subsurface imaging at different sample depths.

Conclusions:

• TM-AFM operating at the phase resonance peak enhances subsurface imaging capabilities.
• This technique allows for quantitative subsurface phase imaging at various depths.
• The findings offer a pathway to more detailed material characterization using AFM.