In order to understand the adsorption and self-assembly of organosilanes, we have studied the adsorption of octyltrichlorosilane (OS) and ocradecyltrichlorosilane (OTS) on an aluminum surface, naturally oxidized. The self-assembled monolayer (SAM) formation was followed with the time-of-flight-secondary ion mass spectrometry (ToF-SIMS) technique. The adsorption is readily detected by means of the Si-containing ions, such as SiH+, SiH-, SIOH ' or SiO2-. Heavier ions that carry information on the surface structure were also identified, such as C8H17SiO2- for an OS adsorption or C18H37SiO2- for an OTS adsorption, The adsorption kinetics can be easily followed by monitoring several characteristic fragments as a function of the adsorption time. The OS adsorption on aluminum appears to have an oscillatory behavior, with a fast adsorption during the first minute followed by a desorption, then a slow adsorption again. All the Si-containing peaks reflect this trend. A possible model that explains the oscillation is given. The aluminum oxide fragments of the type AlxOyHz- exhibit a dramatic decrease with increased coverage, due to the reaction of the active surface sites with the: silanols. Interestingly. the OTS adsorption appears to he monotonic, with a coverage slowly increasing with time. The final achieved coverage is more complete with OTS than with OS. The ToF-SIMS technique appears to be well suited to study the chemical changes and the degree of surface coverage during the adsorption. (C) 2001 Elsevier Science S.V. All rights reserved.
Houssiau, L., & Bertrand, P. (2001). ToF-SIMS study of organosilane self-assembly on aluminum surfaces. Applied Surface Science, 175, 351-356. https://doi.org/10.1016/S0169-4332(01)00087-3 (Original work published 2001)