4.2 Article

Electron reflectivity from clean and oxidized steel surface

Journal

SURFACE AND INTERFACE ANALYSIS
Volume 54, Issue 6, Pages 667-676

Publisher

WILEY
DOI: 10.1002/sia.7079

Keywords

density-functional theory; local density of states; low-energy electron microscopy; mirror microscopy; surface potential

Funding

  1. Technology Agency of the Czech Republic [TN01000008]

Ask authors/readers for more resources

This paper investigates the effect of native oxide on the contrast in SEM images of mild steel surfaces. By in-situ cleaning and removing native oxide, both oxide-free and naturally oxidized areas can be observed simultaneously in the SEM micrographs. The results show that the presence of native oxide starts to affect the SEM images at landing energy below 3 keV, and the contrast between differently oriented grains becomes negligible. The reflectivity contrast between clean and oxidized areas exponentially increases with decreasing landing energy below 3 keV. The study also demonstrates the sensitivity of very low-energy electrons to the electronic structure of the surface.
This paper aims to elucidate the effect of an air-formed native oxide covering mild steel surface on the contrast in the scanning electron microscopy (SEM) images obtained with the landing energy from 5 keV down to 0 eV. Part of the mild steel surface was in-situ cleaned by Ar+ ion sputtering process in order to remove native oxide from the surface. It enabled us to observe the oxide-free and the naturally oxidized area on the mild steel surface simultaneously in the SEM micrographs. Presence of the native oxide starts to play a role in the SEM images acquired at landing energy below roughly 3 keV. Contrast between differently oriented grains situated inside the area covered by the native oxide starts to be negligible with landing energy decreasing below 3 keV, up to some ultra-low values where the contrast increases again. Total reflectivity contrast between the clean and the oxidized area increases exponentially with landing energy decreasing below 3 keV. The reflectivity-versus-energy curves of the cleaned and the naturally oxidized mild steel surface are markedly different. The reflectivity of the electrons is correlated with the density of states (DOS), as is demonstrated at very low landing energies. Sensitivity of the very low-energy electrons to the electronic structure was verified by comparison of the experimental data with the simulations of reflectivities, band structure, and DOS. The theoretical predictions are based on the density-functional theory calculations and they have been performed in energy range corresponding to specular reflectivities of the Fe-BCC (001) orientation. We have also observed that close to the mirror condition, that is, near-zero landing energies, the primary electrons become sensitive to the surface potential differences caused by the work function differences of clean and native oxide-covered steel surfaces.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.2
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available