Journal
APPLIED SURFACE SCIENCE
Volume 323, Issue -, Pages 45-53Publisher
ELSEVIER
DOI: 10.1016/j.apsusc.2014.08.159
Keywords
Photoemission Spectroscopy; SPV; SPS; Metal oxides; Work function; Cu2O
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We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/ atmospheric ions ejected from metallic surfaces (Au, Ag, Cu, Fe, Ni, Ti, Zn, Al) illuminated by a deep ultra-violet (DUV) source under ambient pressure. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used with UPS. This arrangement can be applied in several operational modes: using the DUV source to determine the photoemission threshold (Phi) with 30-50 meV resolution and also the Kelvin probe, under dark conditions, to measure contact potential difference (CPD) between the Kelvin probe tip and the metallic sample with an accuracy of 1-3 meV. We have studied the relationship between the photoelectric threshold and CPD of metal surfaces cleaned in ambient conditions. Inclusion of a second spectroscopic visible source was used to confirm a semiconducting oxide, possibly Cu2O, via surface photovoltage measurements with the KP. This dual detection system can be easily extended to controlled gas conditions, relative humidity control and sample heating/cooling. (C) 2014 The Authors. Published by Elsevier B.V.
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