Sputtering of organic molecular monolayers self-assembled onto Ag(1 1 1) and Au(1 1 1) surfaces

Abstract

Metastable-induced electron spectroscopy (MIES), X-ray and UV photoelectron spectroscopies (UPS) were employed to study sputtering kinetics of monolayers of hexadecanethiol (HDT) molecules, CH 3(CH 2) 15SH, 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 1.3×10 16 cm –2. A distinct low-level damage stage extending up to a dose of about 8×10 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 HDT/Ag.