Angled long tip to tuning fork probes for atomic force microscopy in various environments.

Area of Science:

• Surface science
• Nanotechnology
• Microscopy

Background:

• Conventional tuning fork probes (TFPs) in frequency-modulation atomic force microscopy (FM-AFM) have limitations in force detection directionality.
• Existing TFPs typically utilize short tips, restricting their adaptability to diverse force sensing applications.

Purpose of the Study:

• To enhance the versatility of TFPs for FM-AFM by enabling control over force detection direction.
• To explore new applications of FM-AFM by modifying TFP design and operational parameters.

Main Methods:

• Attaching a long metal tip at a specific angle to a TFP.
• Utilizing combined flexure of the metal tip and tuning fork prong to alter resonance frequency.
• Employing computer simulations and scanning electron microscopy to analyze tip apex oscillatory behavior.
• Conducting FM-AFM experiments in ultrahigh vacuum, air, and water environments.

Main Results:

• The modified TFP demonstrated the ability to change the direction of detectable force by switching resonance frequency.
• Computer simulations and experimental validation confirmed the predicted oscillatory behavior of the TFP tip.
• Successful FM-AFM imaging was achieved in various environments, including air and water.
• Atomic step imaging of highly oriented pyrolytic graphite showed frequency-dependent differences.
• Higher-order flexural modes of the TFP proved advantageous in water by reducing hydrodynamic damping.

Conclusions:

• The novel TFP design significantly expands the application range of FM-AFM.
• The ability to switch force detection direction offers new possibilities for nanoscale force measurements.
• The TFP's performance in different environments, especially water, highlights its robustness and adaptability.