UV-enhanced SEM: towards orientation and electron work function imaging

TL;DR

This paper introduces a UV-enhanced SEM technique using deep-UV co-illumination with controlled polarization and tilt, enabling orientation and work function imaging without metal coatings.

Contribution

It develops a practical in-situ UV co-illumination method with polarization control for SEM, enhancing secondary electron emission and preserving sample integrity.

Findings

Numerical modeling confirms electric field enhancement improves secondary electron yield.

The method allows orientation and work function imaging without metal coatings.

External control mechanisms enable precise UV source positioning and polarization adjustment.

Abstract

Deep-UV ~ 250 nm (4.96 eV) tilted in-situ co-illumination of the sample under imaging by scanning electron microscope (SEM) is developed at a robust and practical instrument level. Precise mechanical control of the lateral position and tilt angle (within 6.5$^\circ$ from a 42$^\circ$ baseline) of the UV-C LED source is achieved using mechanisms external to the vacuum chamber. The incorporated linear polariser (for s-pol. mode illumination) with external polarisation plane adjustment allows for modulation and tuning of tangential $E^{(t)}$ and normal $E^{(n)}$ electric field components and their enhancement for controlled directional electron emission from the surface of the sample. Numerical modelling of E-field enhancement corroborates the expected enhancement in the production of secondary electrons. This modality of SEM imaging does not require metal coatings, preserving sample integrity for subsequent analysis. The feasibility of having linearly polarised incident UV-C light with azimuthal orientation control in $(s,p)$-plane is modeled and discussed.