Ab initio simulation of atomic-scale imaging in noncontact atomic force microscopy.

Area of Science:

• Surface science
• Materials science
• Computational physics

Background:

• Non-contact atomic force microscopy (NC-AFM) is a key technique for surface imaging.
• Understanding image contrast mechanisms is crucial for interpreting NC-AFM data.
• Ab initio simulations provide atomistic insights into tip-sample interactions.

Purpose of the Study:

• To investigate the mechanism of NC-AFM image contrast on semiconductor and metallic surfaces.
• To explore tip-sample interactions, including bond formation and breaking.
• To understand energy dissipation and hysteresis in tip-sample force curves.

Main Methods:

• Utilized ab initio simulations to model NC-AFM experiments.
• Calculated tip-sample force curves during approach and retraction.
• Investigated interactions between a silicon tip and InAs(110) and Ag(110) surfaces.

Main Results:

• Observed bond-formation and bond-breaking processes between a silicon tip and InAs(110) surfaces.
• Similar imaging mechanisms were found on metallic Ag(110) surfaces.
• Significant energy dissipation due to hysteresis in force curves was detected on both surfaces.
• Silicon tips can become contaminated with silver atoms from the surface.

Conclusions:

• Bond-formation/breaking and subsequent energy dissipation explain NC-AFM image contrast on both semiconductor and metallic surfaces.
• Tip contamination can influence imaging mechanisms.
• The observed hysteresis in force curves is a direct consequence of these dynamic tip-sample interactions.