XPS investigation of the interaction between TiCl4(THF)2 and AlEt3 modified SiOx/Si(1 0 0) surfaces

A very important step during the silica-based Ziegler–Natta catalyst synthesis is to decrease the OH content of the oxide’s surface, in order to increase the catalyst activity. A way to eliminate surface hydroxyls is to let the surface react first with a trialkylaluminum reagent. In the present work, the reaction between AlEt3 and Si(1 0 0) wafers covered with thin SiOx layers was studied by XPS, followed by the study of the interaction between TiCl4(THF)2 and the AlEt3 modified substrate. Species such as Si–Et and (Si–O)2–AlEt were identified on the sputtered SiOx/Si substrate after short AlEt3 exposure while (Si–O)–AlEt2 was the main species at further exposures and also when the substrate was not sputtered but only heated at 573 K. Pronounced oxidation of the substrate was observed after TiCl4(THF)2 deposition due to the interaction with THF. The interaction of TiCl4 with the chemisorbed ethylaluminum surface species was found to proceed with the creation of complexes where chlorine atoms and ethyl groups act as bridges between Ti and Al atoms.