TOF-SIMS study of organosilane adsorption on model hydroxyl terminated surfaces

In order to further understand organosilane oscillatory adsorption, we have adsorbed octyltrichlorosilane (C8H17SiCl3 or OS) on model hydroxyl terminated surfaces consisting of a thiol-alcohol self-assembled on gold. The adsorption kinetics was followed with the time-of-flight secondary ion mass spectrometry (TOF-SIMS) technique. The OS adsorption is readily detected by means of a variety of silicon containing ions, some non-specific (e.g. SiH-, SiO2-) and others specific of the OS (C8H17SiO2- or dimers C16H35Si2O4-). Interestingly, a complex non-monotonic adsorption pattern is observed. Moreover, carefully selected ions exhibit different intensity variations with the adsorption time, providing some insight not only on adsorption kinetics, but also on film cross-linking, adsorption sites occupation and even on HCl production due to the trichlorosilane hydrolysis. Small, non-specific fragments (SiH-) are believed to indicate the OS surface coverage whereas large specific fragments are strongly dependent on the interface cross-linking, which reduces their probability of sputtering. (C) 2002 Elsevier Science B.V. All rights reserved.