Electron Beam-Induce Carbon Erosion and the Impact on Electron Probe Microanalysis

Mike Matthews, Stuart Kearns, Ben Buse

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)
155 Downloads (Pure)

Abstract

Electron beam induced carbon contamination is a balance between simultaneous deposition and erosion processes. Net erosion rates for a 25nA 3kV beam can reduce a 5nm C coating by 20% in 60s. Measurements were made on C coated Bi substrates, with coating thicknesses of 5 – 20nm, over a range of analysis conditions. Erosion showed a step-like increase with increasing electron flux density. Both the erosion rate and its rate of change increase with decreasing accelerating voltage. As the flux density decreases the rate of change increases more rapidly with decreasing voltage. Time Dependent Intensity (TDI) measurements can be used to correct for errors, in both coating and substrate quantifications, resulting from carbon erosion. Uncorrected analyses showed increasing errors in coating thickness with decreasing accelerating voltage. Whilst the erosion rate was found to be independent of coating thickness this produces an increasing absolute error with decreasing starting thickness, ranging from 1.5% for a 20nm C coating on Bi at 15kV to 14% for a 5nm coating at 3kV. Errors in Bi M measurement are <1% at 5kV or above but increase rapidly below this both with decreasing voltage and increasing coating thickness to 20% for a 20nm coated sample at 3kV.
Original languageEnglish
JournalMicroscopy and Microanalysis
Early online date16 Nov 2018
DOIs
Publication statusE-pub ahead of print - 16 Nov 2018

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