Energy level alignment at metal-octaethylporphyrin interfaces.
We studied the electronic structure of copper-octaethylporphyrin (CuEOP) adsorbed on three metal surfaces--Ag(001), Ag(111), and Cu(111)--by means of ultraviolet photoelectron spectroscopy (UPS). The adsorption-induced work function shifts saturate roughly beyond two monolayers. The saturation values are substrate dependent, negative, and range from -1.30 to -0.85 eV. This shift is larger than that for tetraphenylporphyrins. The two highest occupied molecular orbitals (HOMO and HOMO-1) of the organic are clearly resolved in the UPS spectra. The origin of the negative work function shift is discussed.
Alkauskas
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NCCR Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland. audrius.alkauskas@unibas.ch
Ramoino
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L
Schintke
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von Arx
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M
Baratoff
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Güntherodt
H-J
HJ
Jung
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