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Accueil > Groupes scientifiques > Electrochimie et Couches Minces > Organisation et Interactions Moléculaires sur les Surfaces

Low Power Plasma Oxidation of Alkyl Monolayer

par Rosso Michel - publié le , mis à jour le

Participants : P. Allongue, J.-N. Chazalviel, F. Ozanam

PhD student : D. Aureau (2008)

Here we investigated the oxidation of alkyl monolayers in a soft oxygen plasma (see page). The plasma chamber was designed and adapted to the IR spectrometer (Fig. 1a). The IR spectra in Fig. 1b, demonstrate that the alkyl chain may be oxidized (positive IR band at 1740 cm-1). Though the CH band (negative band in the region 288-3000 cm-1) seems to disappear completely in the spectra, XPS characterization were essential to demonstrate that oxidation is in fact selective and that the the silicon substrate is not oxidized, if the power of the oxygen plasma is only a few µW/cm3 (Note : the monolayer is totally removed and the silicon surface oxidized within a plasma of power 500 µW/cm3). In fact analysis of the XPS Si2p and C1s spectra (Fig. 1c-d) clearly evidences that the Si-C stay intact during the whole process while the alkyl chains are progressively oxidized (Fig. 1e). Numerical simulation of the plasma (Coll. W. Morscheidt), suggest that singlet molecular oxygen species O2(1Δg) is the dominant reactive species in our conditions.

Figure 1 : (a) Picture of the custom plasma cell ; (b) Series of in situ IR spectra recorded during exposure of a Si-C10 surface in a low power oxygen plasma. (c-d) Variations of the different chemical bonds as derived from Si2p and C1s XPS data analysis. (e) Schematic representation of the progressive organic chain oxidation.

Publications :

[1] D. Aureau, W. Morscheidt, A. Etcheberry, J. Vigneron, F. Ozanam, P. Allongue, and J. N. Chazalviel, "Controlled Oxidation of Alkyl Monolayers Grafted onto Flat Si(111) in an Oxygen Plasma of Low Power Density," Journal of Physical Chemistry C 113 (32), 14418-14428 (2009)