Operation of the Angle Resolving Lens on Theta Probe

Significance of the Topic

Angle resolved XPS enhances surface analysis by capturing both energy and angular distributions of emitted electrons simultaneously. This dual mapping offers detailed insight into surface composition and structure, crucial for materials science, thin film characterization and nanotechnology.

Objectives and Study Overview

This application note explains how the Thermo Scientific Theta Probe is configured in angle resolving mode. It outlines the optical analogy for energy and angle dispersion, and describes lens adjustments required to transform emission angles into spatial distributions on a two dimensional detector.

Methodology and Instrumentation

Ultraviolet and X ray photoelectrons are manipulated by a dual lens system and a hemispherical analyzer equipped with a two dimensional detector. Key elements include

• Lens 1 with large aperture (60 degree acceptance) and high magnification (4x) to collect wide angular range while minimizing beam divergence into Lens 2
• Quadrupole Lens 2 providing independent focal lengths in orthogonal planes to achieve energy dispersion in one axis and angular dispersion in the other
• Hemispherical analyzer acting as both energy filter and focusing device delivering mirrored angle position at the detector exit plane

Key Results and Discussion

By setting Lens 2 focal lengths to image sample position in the energy dispersive plane and sample emission angle in the orthogonal plane, the Theta Probe generates a 2D map. One axis correlates with kinetic energy, the other with emission angle up to 30 degrees. Ray tracing confirms that energy and angular information are decoupled, yielding precise contour images of surface electronic states.

Benefits and Practical Applications

This technique allows simultaneous acquisition of energy spectra and angular distributions without sample rotation. Benefits include

• Accelerated data collection
• Enhanced surface sensitivity and angular resolution
• Capability to study surface texture, molecular orientation and thin film layering

Future Trends and Opportunities

Advances may include integration with in situ environmental analysis, automated data processing using machine learning for pattern recognition, and extension to time resolved angle resolved spectroscopy. Improved lens designs could further expand angular acceptance and energy resolution.

Conclusion

The angle resolving mode on the Theta Probe leverages a specialized quadrupole lens and hemispherical analyzer to produce combined energy and angular dispersion. This approach enhances surface characterization by mapping electronic states in both dimensions simultaneously.

References

Thermo Fisher Scientific Application Note 31003, Operation of the Angle Resolving Lens on Theta Probe