Mechanical, electronical, and chemical properties of a substrate can be tuned by changing its surface composition. Electron-beam chemical lithography was applied successfully in the literature to self-assembled monolayers (SAMs) of thiols deposited on gold [1]. Generally, the focussed electron beam energy belongs to the keV range. At such high energy, the chemical specificity is low due to the large number of dissociating open channels, and the release of secondary low-energy electrons. By contrast, low-energy (0-20 eV) electrons (LEE) allow to induce, control, and orientate chemical reactivity, by initiating selective and efficient dissociative processes at sub-excitation energies [2].

Low-energy electron interactions and induced surface chemistry were studied in thiol SAMs deposited on gold. Selective modification of terminal functions in 11-Mercapto-undecanoic acid SAMs [3], and of aromatic spacers in terphenylthiol SAMs will be discussed.

LEE irradiations are performed using a commercial gun, which supplies, depending on electron energy, a current of 0.5-5.0 mA on a ~2-7 mm spot, with a resolution of about 500 meV. Exposures of typically 10-700 e^- per adsorbed molecule (uncertainty estimated to 50%) are used for processing. The electron induced primary processes are studied by electron induced desorption (ESD) of neutral fragments. The resulting chemical modifications of the substrates are probed by HREEL vibrational spectroscopy (High Resolution Electron Energy Loss Spectroscopy).

[1] e.g. N. Ballav et al., Angew. Chem. 47 (2008) 1421; A. Gölzhäuser et al. Adv.Mat. 13 (2001) 806.

[2] Reviews. I. Bald et al., Int. J. Mass Spectrometry 277 (2008) 4 ; A. Lafosse et al., Progress Surf. Sci. 84 (2009) 177 and References therein; C.R. Arumainayagam et al., Surf. Sci. Rep. 65 (2010) 1

[3] F. Tielens et al., J. Phys. Chem. C 112 (2008) 182; F. Thery-Merland et al., Sensors & Actuators B 114 (2006) 223