Effect of a-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 a-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 a-heteroatoms next to the alkene function improved both the reactivity and surface coverage on H-terminated Si(111) surfaces.