Effect of α-Heteroatoms on the Formation of Alkene-Derived Monolayers on H-Si(111): A Combined Experimental and Theoretical Study.

We investigate herein whether the reactivity and surface coverage of 1-alkenes toward hydrogen-terminated Si(111) surfaces [H-Si(111)] can be improved by introducing heteroatoms such as oxygen and sulfur at the α-position next to the alkene functional group. To this end, the reactivity of 1-pentene, 1-pentyne, vinyl ethyl ether, and vinyl ethyl sulfide toward H-Si(111) and the surface coverage of the resulting monolayers were studied and compared. All modified surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), and infrared absorption reflection spectroscopy (IRRAS). Quantum chemical calculations were performed to calculate the activation barriers and driving forces for monolayer formation at the M11-L/6-311G(d,p) level of theory. Both experiments and theory indicate that the presence of α-heteroatoms next to the alkene function improved both the reactivity and surface coverage on H-terminated Si(111) surfaces.