Regensburg 2013 – scientific programme

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DS: Fachverband Dünne Schichten

DS 32: Poster Session IV: Atomic layer deposition; Organic thin films; Organic Electronics and Phototovoltaics; Organic Materials for Spintronics - from spinterface to devices; Thin film photovoltaic materials and solar cells

DS 32.27: Poster

Thursday, March 14, 2013, 17:00–20:00, Poster B2

The effects of oxygen exposure on copper phthalocyanine thin films — •Tomoki Sueyoshi^1,2, Masaki Ono¹, Hiroshi Tomii³, Masakazu Nakamura³, and Nobuo Ueno¹ — ¹Graduate School of Advanced Integration Science, Chiba University, Japan — ²Peter Grünberg Institut (PGI-3), JARA, Forschungszentrum Jülich, Germany — ³Graduate School of Engineering, Chiba University, Japan

The exposure of organic semiconductor thin films to gas atmospheres, such as O2, water vapor, and air, has been reported to influence their electronic properties. The gas exposure consequently results in a short lifetime and low performance of organic devices under ambient atmosphere. Such effects have been discussed from a viewpoint of electronic properties of organic layers in relation to chemical interactions between organic molecules and gas molecules. However, there is little known about the correlation between the gas exposure effects and structural properties of organic thin films.

Here, we demonstrate that the effects of O2 gas exposure depend on the molecular packing structure of organic thin films. We investigated electronic states of a copper phthalocyanine (CuPc) thin film on graphite before and after O2 exposure using ultrahigh-sensitivity ultraviolet photoelectron spectroscopy. The highest occupied molecular orbital state of CuPc with a lying-down molecular orientation was not affected by 1 atm O2 exposure while that of CuPc with a tilted-up orientation shifted toward the Fermi level after the exposure. The O2 exposure effects may originate from a weak disorder in the molecular packing structure induced by O2 diffusion into the film.