Desorption of organic overlayers by Ga and C60 bombardment

This paper reviews our recent work on computer simulations of Ga and C60 bombardment of thin organic overlayers deposited on metal substrate. A multilayer of benzene, a monolayer of PS4 on Ag{1 1 1} and a self-assembled monolayer of octanethiol molecules on Au{1 1 1} were irradiated with 15 keV monoatomic (Ga) and polyatomic (C60) projectiles that are recognized as valuable sources for desorption of high mass particles in secondary ion and neutral mass spectrometry (SIMS/SNMS) experiments. The results indicate that the sputtering yield decreases with the increase of the binding energy and the average kinetic energy of parent molecules is shifted toward higher kinetic energy. Although the total sputtering yield of organic material is larger for 15 keV C60, the impact of this projectile leads to a significant fragmentation of ejected species. As a result, the yield of the intact molecules is comparable for C60 and Ga projectiles. Our results indicate that the chemical analysis of thin organic films performed by detection of sputtered neutrals will not benefit from the use of C60 projectiles.