Thermal reactivity of pyrrole and its methyl derivatives on silicon (111) hydride surfaces

Abstract

To understand how steric and molecular geometry may influence silicon surface reactions, thermal grafting of pyrrole and its methyl derivatives, namely 2,4-Dimethylpyrrole and 2,5-dimethylpyrrole was performed on planar silicon (111) hydride surfaces to form ultrathin monolayer (<0.5 nm). The samples were then analyzed with detailed XPS and FTIR-ATR to elucidate the chemical profiles on the surfaces while AFM and contact angle measurements were taken to examine physical characteristics. Together with DFT calculations, we had shown the different geometry of pyrrole derivatives can alter the way surface bond were formed. From our analysis, Pyrrole and 2,4-Dimethylpyrrole was found to react via Si-N bonding while 2,5-Dimethylpyrrole may have been grafted via Si-C linkage. Furthermore, the close proximity of between silicon surface atom and the aromaticity of pyrrole in conjugation to methyl group had help to reduce oxidation effect of the surface during thermal reaction. These corroborations between structure and reactivity are considered to be highly important towards realization of stable sub-nanometer ultrathin organic monolayer grafts on silicon surface, especially in the context for advanced molecular electronics.