Orientation-controlled surface immobilization of alkyl molecules

Narita, Ayumi; Baba, Yuji  ; Sekiguchi, Tetsuhiro  ; Shimoyama, Iwao   ; Hirao, Norie; Yaita, Tsuyoshi

Self-assembled monolayer (SAM) has been focused as new thin film materials because SAMs have high chemical stability. In this study, we have investigated that the chemical states of the interfaces between mercapto-propyl-trimethoxy-silane (MPTS) molecules and inorganic substrates using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray fine structure (NEXAFS). It was found that the MPTS molecules form strong chemical bond with the Au substrate through thiol groups. For XPS spectra, the results showed that thiol groups in MPTS form covalent bonds with Au, while alkoxide groups are bound with sapphire. As a result, MPTS molecules are adsorbed on Au with thiol groups and alkoxide groups are located at the upper side, while the direction of MPTS molecules on sapphire surface is opposite. It is concluded that MPTS molecules can be used as a mold to immobilize the other organic molecules through thiol or alkoxide groups.