Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 9: Organic films I

O 9.8: Vortrag

Montag, 27. März 2006, 16:45–17:00, TRE Phys

High thermal stability of electron cross-linked aromatic self-assembled monolayers — •Mohamed El-Desawy, Andrey Turchanin, and Armin Gölzhäuser — Physik Supramolekularer Systeme, Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld

We report on the thermal stability of e-beam cross-linked biphenylthiol (BPT) self-assembled monolayers (SAMs) on gold surfaces. The monolayers were formed from solution and cross-linked by low-energy electrons (50-200 eV). The SAMs were then thermally annealed in ultra high vacuum. Long annealing times and slow heating rates were employed to follow temperature induced changes at conditions close to thermal equilibrium. After each heating step, the films were analyzed by X-ray photoelectron spectroscopy (XPS). For non cross-linked BPT, at ~420K the carbon coverage abruptly decreases to ~20%, which is accompanied by a breaking of C-S bonds. In cross-linked BPT, despite a C-S bond cleavage in the same temperature range, the carbon matrix shows only gradual changes with increasing temperature. Even at ~1000K, the SAM coverage has only decreased to ~80%. Hence, cross-linked SAMs show a much higher thermal stability than non cross-linked ones. This is of importance for technological applications of SAM coatings.