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Electronic structure differences between H(2)-, Fe-, Co-, and Cu-phthalocyanine highly oriented thin films observed
T M Willey1, M Bagge-Hansen, J R I Lee
1Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, California 94550, USA. willey1@llnl.gov
The Journal of Chemical Physics
|July 26, 2013
Summary
Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals molecular orientation in phthalocyanine thin films. Sapphire substrates promote upright orientations, while gold substrates lead to prostrate orientations, with distinct electronic structures observed.
Area of Science:
- Materials Science
- Surface Science
- Spectroscopy
Background:
- Phthalocyanines are versatile macrocyclic molecules used in semiconductor applications.
- Understanding their orientation and electronic structure is crucial for optimizing device performance.
Purpose of the Study:
- To quantitatively probe the orientation and electronic structure of H2-, Fe-, Co-, and Cu-phthalocyanine thin films.
- To investigate the influence of substrate (sapphire vs. gold) on molecular orientation.
Main Methods:
- Angular-dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.
- Analysis of carbon, nitrogen K-edges, and metal L-edges.
Main Results:
- Phthalocyanine films on sapphire exhibit upright molecular orientations.
- Films on gold substrates (up to 50 nm) show prostrate molecular orientations.
- Distinct spectral features at metal L-edges reveal differences in electronic structure and orbital contributions (e.g., Cu vs. Fe/Co).
Conclusions:
- NEXAFS spectroscopy is a powerful tool for determining molecular orientation and electronic structure in thin films.
- Substrate choice significantly impacts phthalocyanine thin film morphology and electronic properties.
- Metal identity in organometallic phthalocyanines influences electronic transitions and their orientation dependence.
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