Materials for mass standards: long-term stability of PtIr and Au after hydrogen and oxygen low-pressure plasma cleaning

The recontamination and long-term stability of materials suitable for mass standards was studied with x-ray photoemission spectroscopy after low-pressure plasma cleaning using hydrogen and oxygen. The cleaned samples were stored in air or argon at ambient pressure and under UHV conditions and the su...

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Bibliographic Details
Published inMetrologia Vol. 49; no. 6; pp. 615 - 627
Main Authors Fuchs, P, Marti, K, Russi, S
Format Journal Article
LanguageEnglish
Published Bristol IOP Publishing 01.12.2012
Subjects
Chemical contaminants
Contamination
Hydrogen
Oxygen
Pressure
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Summary:The recontamination and long-term stability of materials suitable for mass standards was studied with x-ray photoemission spectroscopy after low-pressure plasma cleaning using hydrogen and oxygen. The cleaned samples were stored in air or argon at ambient pressure and under UHV conditions and the surface chemical state was monitored continuously. We found the recontamination exhibits initially self-limited growth. In the long term over three years, we found no indication for further accumulation of contaminants. From the uncertainties of our observations we provide an upper limit for the long-term contamination which is the lowest of all the results published up to now. The stability of PtIr and Au upon different cleaning processes and storage conditions is described in detail.
ISSN:0026-1394
1681-7575
DOI:10.1088/0026-1394/49/6/615