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EELS and low‐energy electron emission of clean and oxygen‐exposed tantalum
Author(s) -
Palacio C.,
MartínezDuart J. M.
Publication year - 1990
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740151107
Subject(s) - tantalum , fermi level , atomic physics , excited state , x ray photoelectron spectroscopy , chemistry , spectral line , electron , secondary electrons , density of states , auger electron spectroscopy , secondary emission , condensed matter physics , ion , physics , nuclear magnetic resonance , organic chemistry , quantum mechanics , astronomy , nuclear physics
Abstract The electron energy‐loss spectra (EELS) associated with 4f and 5p excitations, and the secondary electron spectra (SES) have been used to study the oxidation of a clean polycrystalline tantalum surface. For the clean and oxygen‐exposed surfaces, the EELS results are discussed in terms of bulk and surface plasmons as well as interband transitions to unoccupied states above the Fermi level ( E F ). The secondary electron spectra have been used as a fingerprint for the density of unoccupied states above E F . The changes observed in the EEL spectrum upon oxygen exposure are explained as being due to oxide formation, in agreement with previous results by XPS and AES. The features observed above the NVV and OVV Auger transitions, in both the clean and oxidized surfaces, are described as auto‐ionization emission due to the decay of electrons that have been excited resonantly from the 4f and 5p levels to states well above the states well above the Fermi energy. The excitation process has been identified also in the EEL spectra.