TY - JOUR
T1 - Electronic states of titanyl phthalocyanine films on alkanethiolate self-assembled monolayers probed by two-photon photoemission
AU - Ogura, Munehisa
AU - Shibuta, Masahiro
AU - Eguchi, Toyoaki
AU - Nakajima, Atsushi
N1 - Funding Information:
This work is partly supported by MEXT-Supported Program for the Strategic Research Foundati on at Private Universities, 2009–2013 and by MEXT-Grant-in-Aid for Young Scientists (B) (No. 25810010 ).
PY - 2014/8
Y1 - 2014/8
N2 - We studied both occupied and unoccupied states of titanyl phthalocyanine (TiOPc) films formed on an octanethiolate self-assembled monolayer (SAM) on an Au(1 1 1) surface fabricated in a wet chemical process using two-photon photoemission (2PPE) spectroscopy. A 1.90-nm-thick layer of TiOPc formed an unoccupied state at 2.9 eV above the Fermi level. This state was resonantly enhanced at 4.3-4.4 eV photon energy, suggesting that electrons were excited from the highest occupied molecular orbital of TiOPc. The 2PPE measurements of photon energy dependence and light polarization selectivity revealed that the unoccupied state originates from a charge transfer exciton not observed in organic thin films deposited on bare metallic substrates. The formation of a charge transfer exciton implies that the SAM strongly insulates the molecular monolayer.
AB - We studied both occupied and unoccupied states of titanyl phthalocyanine (TiOPc) films formed on an octanethiolate self-assembled monolayer (SAM) on an Au(1 1 1) surface fabricated in a wet chemical process using two-photon photoemission (2PPE) spectroscopy. A 1.90-nm-thick layer of TiOPc formed an unoccupied state at 2.9 eV above the Fermi level. This state was resonantly enhanced at 4.3-4.4 eV photon energy, suggesting that electrons were excited from the highest occupied molecular orbital of TiOPc. The 2PPE measurements of photon energy dependence and light polarization selectivity revealed that the unoccupied state originates from a charge transfer exciton not observed in organic thin films deposited on bare metallic substrates. The formation of a charge transfer exciton implies that the SAM strongly insulates the molecular monolayer.
KW - Charge transfer exciton
KW - Self-assembled monolayer
KW - Titanyl phthalocyanine
KW - Two-photon photoemission spectroscopy
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U2 - 10.1016/j.elspec.2014.06.011
DO - 10.1016/j.elspec.2014.06.011
M3 - Article
AN - SCOPUS:85028161705
SN - 0368-2048
VL - 195
SP - 272
EP - 277
JO - Journal of Electron Spectroscopy and Related Phenomena
JF - Journal of Electron Spectroscopy and Related Phenomena
ER -