The Reaction of Tetrakis(dimethylamido)titanium with Self-Assembled Alkyltrichlorosilane Monolayers Possessing −OH, −NH<sub>2</sub>, and −CH<sub>3</sub> Terminal Groups

The reactions of tetrakis(dimethylamido)titanium, Ti[N(CH<sub>3</sub>)<sub>2</sub>]<sub>4</sub>, with alkyltrichlorosilane self-assembled monolayers (SAMs) terminated by −OH, −NH<sub>2</sub>, and −CH<sub>3</sub> groups have been investigated with X-ray photoelectron spectroscopy (XPS). For comparison, a chemically oxidized Si surface, which serves as the starting point for formation of the SAMs, has also been investigated. In this work, we examined the kinetics of adsorption, the spatial extent, and stoichiometry of the reaction. Chemically oxidized Si has been found to be the most reactive surface examined here, followed by the −OH, −NH<sub>2</sub>, and −CH<sub>3</sub> terminated SAMs, in that order. On all surfaces, the reaction of Ti[N(CH<sub>3</sub>)<sub>2</sub>]<sub>4</sub> was relatively facile, as evidenced by a rather weak dependence of the initial reaction probability on substrate temperature (<i>T</i><sub>s</sub> = −50 to 110 °C), and adsorption could be described by first-order Langmuirian kinetics. The use of angle-resolved XPS demonstrated clearly that the anomalous reactivity of the −CH<sub>3</sub> terminated SAM could be attributed to reaction of Ti[N(CH<sub>3</sub>)<sub>2</sub>]<sub>4</sub> at the SAM/SiO<sub>2</sub> interface. Reaction on the −NH<sub>2</sub> terminated SAM proved to be the “cleanest”, where essentially all of the reactivity could be associated with the terminal amine group. In this case, we found that approximately one Ti[N(CH<sub>3</sub>)<sub>2</sub>]<sub>4</sub> adsorbed per two SAM molecules. On all surfaces, there was significant loss of the N(CH<sub>3</sub>)<sub>2</sub> ligand, particularly at high substrate temperatures, <i>T</i><sub>s</sub> = 110 °C. These results show for the first time that it is possible to attach a transition metal coordination complex from the vapor phase to a surface with an appropriately functionalized self-assembled monolayer.