The binding of multi-functional organic molecules on silicon surfaces

Abstract

We have investigated the chemical, electronic, and vibrational properties of multi-functional organic molecules, including pyrazine, pyrimidine, s-triazine, acetylethyne, cyanoacetylene, diacetylene, benzadehyde and acetophenone, on the Si(111)-7??7 and Si(100)-2??1 surfaces using combined HREELS, XPS, UPS, STM, and DFT theoretical calculations. Our results demonstrate that the silicon surfaces can be efficiently functionalized by covalent attachment of the multi-functional organic molecules. For nitrogen-containing aromatic molecules/Si(111)-7??7 system, experimental and DFT calculation results clearly demonstrate that the attachment occurs via [4+2]-like cycloaddition involving at least one nitrogen atom. In the case of acetylethyne, the different binding configurations on Si(111)-7??7 and Si(100)-2??1 surfaces exhibit the influence from the surface structures. Cyanoacetylene and diacetylene, though having similar chemical structures, react with Si(111)-7??7 via [4+2]-like and [2+2]-like cycloadditions, respectively. Moreover, experimental and DFT calculation results show that the covalent attachment of benzadehyde and acetophenone on Si(100) occurs in a highly selective manner through the direct interaction of both C and O atoms of the carbonyl group with a Si=Si dimer.