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Infrared spectroscopic study of the CO‐mediated decrease of the percolation threshold during the growth of ultrathin metal films on MgO(001)
Author(s) -
Lust M.,
Priebe A.,
Fahsold G.,
Pucci A.
Publication year - 2002
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.1236
Subject(s) - percolation threshold , metal , percolation (cognitive psychology) , infrared , analytical chemistry (journal) , ionic bonding , spectral line , copper , conductivity , deposition (geology) , transmittance , materials science , relaxation (psychology) , chemistry , electrical resistivity and conductivity , ion , optics , metallurgy , optoelectronics , organic chemistry , astronomy , neuroscience , sediment , engineering , biology , psychology , paleontology , social psychology , chromatography , physics , electrical engineering
Metals are known to grow three‐dimensionally on clean ionic crystal surfaces with low surface energies. As a consequence, the naturally grown films consist of islands and are non‐conductive up to the percolation threshold, which is at ∼1 nm for iron films grown on MgO(001) at room temperature and is much larger for noble metals and higher temperatures, respectively. In this paper we show that CO exposure at ∼10 −8 mbar during deposition modifies the growth on MgO(001) for iron and copper. The development of infrared transmission spectra versus metal film thickness clearly is changed by CO exposure. The spectral differences correspond to a significant percolation threshold decrease induced by CO. Infrared conductivity parameters calculated from transmittance spectra indicate that the surface relaxation of the free charge carriers is decreased due to CO exposure during growth but the plasma frequency is unchanged. Copyright © 2002 John Wiley & Sons, Ltd.