Sputtering of organic molecular monolayers self-assembled onto Ag(111) and Au(111) surfaces

Metastable-induced electron spectroscopy (MIES), X-ray and UV photoelectron spectroscopies (UPS) were employed to study sputtering kinetics of monolayers of hexadecanethiol (HDT) molecules, CH3(CH2)(15)SH, self-assembled on Au(1 1 1) and Ag(1 1 1) substrates under 800 eV He+-ion bombardment in the dose range up to 1.3 x 10(16) cm(-2). A distinct low-level damage stage extending up to a dose of about 8 x 10(13) cm(-2) could be distinguished in sputtering kinetics of the HDT/Ag system. The bands of enhanced electron emission from specific molecular orbitals arising in the difference MIES and UPS spectra and evolving in the course of ion irradiation of HDT/Ag and HDT/Au were identified by juxtaposing with the spectra of hexadecane and octadiene. In both systems, ion bombardment was found to induce the formation of C=C double bonds. The character of sputtering kinetics depends on the substrate. The HDT/Au system is characterized by a considerably higher rate of destruction of the film, with the initial sputtering yield being nearly twice as great as that for HDTI/Ag. (C) 2002 Elsevier Science Ltd. All rights reserved.