Tip-induced deformation of polystyrene latex reference nanoparticles in atomic force microscopy

Area of Science:

• Nanotechnology
• Materials Science
• Metrology

Background:

• Atomic force microscopy (AFM) is commonly used for sizing polystyrene latex (PSL) nanoparticles.
• Standard AFM sizing relies on particle height from 3D images, but PSL deformation during preparation and imaging presents a challenge.

Purpose of the Study:

• To investigate the impact of cantilever tilt, tip shape, and setpoint voltage on tip-induced deformation of PSL nanoparticles.
• To understand how these factors influence height measurements in AFM nanoparticle metrology.

Main Methods:

• Characterization of AFM tips using scanning electron microscopy and a multilayer Si/SiO2 tip characterizer.
• Analysis of tip-induced deformation of PSL nanoparticles under varying operational conditions.

Main Results:

• Asymmetric imaging geometry induces plastic flow, shifting the maximum particle height from the center.
• This shape change can lead to an apparent height increase in PSLs smaller than 40 nm.
• AFM height analysis algorithms equating apparent height with the highest measured point are affected.

Conclusions:

• Tip-induced deformation significantly affects AFM measurements of PSL nanoparticle height.
• The findings have critical implications for the accuracy and reliability of AFM-based nanoparticle metrology.
• Understanding deformation mechanisms is crucial for precise nanoparticle characterization.