Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 77: Focussed Session: Towards a Quantitative Understanding of Complex Adsorption Structures: Surface Science goes Organic III

O 77.4: Talk

Thursday, April 3, 2014, 17:00–17:15, TRE Phy

Structure and ordering of thin organic layers on silicon surfaces — •Thomas Schmidt, Christian Schulz, Torsten Wilkens, and Jens Falta — Universität Bremen, Germany

The adsorption and growth of organic layers on silicon surfaces offers the opportunity to combine the application potential of organic materials with silicon technology, e.g., for hybrid solar cells, transistors, or biosensors [1–3].

We investigated thin films of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) and copper phthalocyanine (Cu-PC) on Si(111) surfaces that had been passivated with monolayer deposits of either Ag or Bi. Scanning tunneling microscopy and high-resolution low-energy electron diffraction show a drastic improvement of the structural order and morphology as compared to deposition on clean Si(111).

PTCDA forms smooth layers with a herringbone structure on Ag-terminated as well as Bi-terminated Si(111). For the latter case, x-ray photoelectron spectroscopy indicates a charge transfer from the carbonyl oxygen of the anhydride groups to the substrate. Additional structural phases are observed in the initial growth stages, which can be suppressed by deposition at elevated temperatures.

With respect to the structural order of Cu-PC films, Ag turns out to be superior to Bi as passivating agent and leads to well-ordered domains with rhombic (nearly square) unit cells.

[1] D.R.T. Zahn et al., Solar Energy 80, 707 (2006).
[2] L. De Stefano et al., Sensors 7, 214(2007).
[3] Zhongming Wei et al., Appl. Phys. Lett. 95, 033304 (2009).