Electronic Coupling Effects and Charge Transfer between Organic Molecules and Metal Surfaces

We employ a variant of optical absorption spectroscopy, namely in situ differential reflectance spectroscopy (DRS), for an analysis of the structure-properties relations of thin epitaxial organic films. Clear correlations between the spectra and the differently intense coupling to the respective substrates are found. While rather broad and almost structureless spectra are obtained for a quaterrylene (QT) monolayer on Au(111), the spectral shape resembles that of isolated molecules when QT is grown on graphite. We even achieve an efficient electronic decoupling from the subjacent Au(111) by inserting an atomically thin organic spacer layer consisting of hexa-peri-hexabenzocoronene (HBC) with a noticeably dissimilar electronic behavior. These observations are further consolidated by a systematic variation of the metal substrate (Au, Ag, and Al), ranging from inert to rather reactive. For this purpose, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is chosen to ensure comparability of the molecular film structures on the different metals, and also because its electronic alignment on various metal surfaces has previously been studied with great intensity. We present evidence for ionized PTCDA at several interfaces and propose the charge transfer to be related to the electronic level alignment governed by interface dipole formation on the respective metals.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2010

Author dc:creator

• Forker, Roman

Contributors dc:contributor

• Leo, Karl
• Sokolowski, Moritz

• organic semiconductors
• dye molecules
• QT
• HBC
• PTCDA
• organic molecular beam epitaxy (OMBE)
• differential reflectance spectroscopy (DRS)
• scanning tunneling microscopy (STM)
• low energy electron diffraction (LEED)
• organische Halbleiter
• Farbstoffmoleküle
• organische Molekularstrahlepitaxie
• differentielle Reflexionsspektroskopie
• Rastertunnelmikroskopie
• niederenergetische Elektronenbeugung