Abstract
Dual mode charge compensation has been used successfully for many years to enable X‐ray photoelectron spectroscopy (XPS) analysis of a variety of insulating samples. This approach uses a combination of low energy electrons and argon to compensate for positive charge build‐up during irradiation by X‐rays. Whilst this method works with no detectable side effects in most cases, it was recently reported that the chemical bonding states of some Cr(VI) oxides may be modified by prolonged exposure to the flood source. In this work, we demonstrate successful dual mode charge compensation of CrO3 with no discernible sample modification from the flood source. Under the same flood source conditions, we extend the analysis to other systems known to undergo reduction and present charge compensated XPS data for V2O5 and a copper‐based metal‐organic framework (MOF) showing little or no modification from the flood source, even with prolonged exposure.
Highlights
WHY USE DUAL MODE CHARGE COMPENSATION?Electron ejection via photoemission is the underlying basis of X‐ray photoelectron spectroscopy (XPS); for meaningful analysis of surfaces by XPS, the net positive charge on the surface from this emission must be balanced
Monochromatic X‐ray sources, minimise stray secondary electrons due to the indirect illumination of the surface by the source, and any spectrum from an insulating material will gradually shift to higher binding energies becoming a mixture of broadened and displaced peaks making chemical state identification misleading or impossible, unless an external charge compensation source is used.[1,2]
To study the effect of the neutraliser on these copper species, we have investigated the NOTT‐100 metal‐organic framework (MOF), which is often used for hydrogen adsorption; the MOF itself is composed of a Cu(II) centre, linked by H4BPTC moieties.[25]
Summary
Funding information Engineering and Physical Sciences Research Council (EPSRC), Grant/Award Number: PR16195. Dual mode charge compensation has been used successfully for many years to enable X‐ray photoelectron spectroscopy (XPS) analysis of a variety of insulating samples This approach uses a combination of low energy electrons and argon to compensate for positive charge build‐up during irradiation by X‐rays. In the remainder of this paper, we present a recently developed dual mode charge compensation method which has been shown to compensate Cr(VI) oxide without any significant reduction, even when prolonged sample analysis times are required This enables the user to retain the previously explained benefits of combined electron/argon ion compensation during conventional XPS analysis, whilst maintaining the chemical integrity of their samples. All powders were gently pressed into the wells of a Thermo Scientific powder holder plate, whilst flake‐like materials were held with a small section of a double‐sided carbon tape
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