Quantifying work function differences using low-energy electron microscopy: The case of mixed-terminated strontium...

Area of Science:

• Surface science
• Materials characterization
• Electron microscopy

Background:

• Accurate local work function measurement is crucial for many surface-dependent applications.
• Low-energy electron microscopy (LEEM) offers high lateral resolution and sensitivity to electrostatic potentials, making it suitable for work function mapping.
• Work function discontinuities on surfaces generate lateral electrostatic fields that can distort LEEM images, creating artifacts.

Purpose of the Study:

• To investigate and quantify the artifacts caused by lateral electrostatic fields in LEEM imaging of surfaces with varying work functions.
• To develop a more accurate method for determining work function differences at surface discontinuities.

Main Methods:

• Utilizing ray-tracing simulations to model the behavior of low-energy electrons in the presence of lateral electrostatic fields.
• Analyzing LEEM data from a mixed-terminated strontium titanate surface.
• Comparing standard LEEM image analysis with results from detailed ray-tracing simulations.

Main Results:

• Ray-tracing simulations demonstrate that artifacts from lateral fields can extend over hundreds of nanometers.
• Standard image analysis methods overestimate the true work function difference by a factor of 1.6 near discontinuities.
• Integrating LEEM data with ray-tracing simulations yields a more reliable work function difference estimate.

Conclusions:

• Lateral electrostatic fields at work function discontinuities introduce significant artifacts in LEEM.
• Standard LEEM analysis overestimates work function differences, necessitating correction.
• A combined approach of LEEM and ray-tracing simulations enhances the accuracy of local work function measurements.