Ambient-pressure atomic force microscope with variable pressure from ultra-high vacuum up to one bar

Area of Science:

• Surface Science
• Nanotechnology
• Materials Science

Background:

• Atomic Force Microscopy (AFM) is a powerful surface analysis technique.
• Environmental control is critical for understanding nanoscale surface interactions.
• Existing AFM systems often have limited pressure ranges.

Purpose of the Study:

• To design and demonstrate an ambient-pressure atomic force microscope (AP-AFM).
• To enable AFM measurements in controlled environments from ultra-high vacuum (UHV) to atmospheric pressure.
• To investigate the influence of gas environment and pressure on tip-surface interactions.

Main Methods:

• Utilized a combination of turbo-molecular and ion pumps for UHV.
• Employed a leak valve and gas manifold for introducing high-purity gases.
• Performed topography, friction, local conductance mapping, and force spectroscopy.
• Studied highly ordered pyrolytic graphite (HOPG) under variable pressure conditions.

Main Results:

• Achieved atomically resolved stick-slip images and force spectroscopy at variable pressures.
• Demonstrated significant pressure- and gas-dependent adhesion between AFM tip and HOPG.
• Observed changes in adhesion force upon exposure to lab air, oxygen, and methane.
• Confirmed deposition of airborne hydrocarbon impurities alters adhesion forces.

Conclusions:

• The AP-AFM system offers versatile AFM measurements in controlled environments from UHV to 1 bar.
• Surface adhesion is highly sensitive to the surrounding gas environment and pressure.
• Airborne impurities significantly impact surface wettability and adhesion forces.