Sample thickness determination by scanning transmission electron microscopy at low electron energies

Area of Science:

• Materials Science
• Physics
• Electron Microscopy

Background:

• Accurate sample thickness determination is crucial for quantitative analysis in transmission electron microscopy (TEM).
• Existing methods may have limitations, necessitating new approaches for precise thickness measurements.

Purpose of the Study:

• To present a novel method for determining local sample thickness using scanning transmission electron microscopy (STEM).
• To validate the method across a range of materials and electron energies.

Main Methods:

• Utilizing STEM with primary electron energies below 30 keV.
• Measuring image intensity relative to the incident electron beam.
• Comparing experimental data with Monte Carlo simulations using screened Rutherford and Mott scattering cross-sections.

Main Results:

• The method was successfully tested on materials with atomic numbers ranging from 3.5 (fluorenyl hexa-peri-hexabenzocoronene) to 74 (tungsten).
• Investigations covered primary energies of 15 and 30 keV.
• The technique demonstrated accuracy for sample thicknesses between 50 and 400 nm.

Conclusions:

• The developed method provides a reliable way to measure local sample thickness in STEM.
• This technique is applicable to diverse materials and electron beam energies relevant for nanoscale analysis.