Journal article
Scanning Tunneling Microscopy Study of the Structure and Orbital-Mediated Tunneling Spectra of Cobalt(II) Phthalocyanine and Cobalt(II) Tetraphenylporphyrin on Au(111): Mixed Composition Films
Langmuir, Vol.20(11), pp.4413-4421
05/25/2004
Handle:
https://hdl.handle.net/2376/104342
PMID: 15969147
Abstract
Binary thin films of cobalt(II) phthalocyanine (CoPc) and cobalt(II) tetraphenylporphyrin (CoTPP) were prepared at submonolayer coverage on Au(111)/mica substrates by vapor deposition. All sample preparation and analysis were done under an ultrahigh vacuum. Scanning tunneling microscopy (STM) constant-current images of CoPc/CoTPP mixtures showed two close-packed surface structures, with different compositional percentages and some disorder. CoPc was also observed exclusively in one-dimensional chains and as single, isolated molecules below 220 K. Occupied and unoccupied orbital energy levels were identified by STM and tunnel-diode-based orbital-mediated tunneling spectroscopy. Occupied energy levels were also confirmed by ultraviolet photoelectron spectroscopy. The transient oxidation of the Co d z 2 orbital is identified in STM dI/dV(V) curves just negative of the 0 V sample bias for both molecules. Nearly identical constant-current contours are observed over the central Co2+ ions of CoTPP and CoPc, indicating that the attenuation of the d z 2 orbital-mediated tunneling current induced by the structure of TPP relative to Pc is at most a factor of about 10. The orbital-mediated tunneling spectra of CoTPP and CoPc are distinctly different and allow these structurally similar species to be differentially identified.
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Details
- Title
- Scanning Tunneling Microscopy Study of the Structure and Orbital-Mediated Tunneling Spectra of Cobalt(II) Phthalocyanine and Cobalt(II) Tetraphenylporphyrin on Au(111): Mixed Composition Films
- Creators
- Dan E BarlowL ScudieroK. W Hipps
- Publication Details
- Langmuir, Vol.20(11), pp.4413-4421
- Academic Unit
- Chemistry, Department of
- Publisher
- American Chemical Society
- Identifiers
- 99900546512701842
- Language
- English
- Resource Type
- Journal article