title: Ultrathin poly(ethylene glycol) monolayers formed by chemical vapor deposition on silicon substrates.
abstract: Poly(ethylene glycol) (PEG) monolayer was formed through the chemisorption of a vapor phase organosilane. Photochemically cleaned silicon substrate covered with native oxide (SiO2/Si) was exposed to a vapor of an organosilane, that is, 2-(methoxy[polyethyleneoxy]propyl) trimethoxysilane (MPEOPS) for 1-7 h at 150 degrees C. The resulting sample surfaces became relatively hydrophobic showing a static water-contact angle of ca. 67 +/- 2 degrees and their thickness was ellipsometrically measured to be ca. 0.8 +/- 0.1 nm. Atomic force microscopy confirmed that the sample surface was extremely smooth and homogeneous. Isoelectric point of the MPEOPS-monolayer-covered SiO2/Si substrate was measured to be at around pH 4.9, which was close to that of the methoxytri(ethylene glycol)-terminated alkanethiol SAM on gold (pH 4.3). Furthermore, we demonstrated micropatterning of the MPEOPS monolayer based on a direct photolithography using 172 nm VUV light through a photomask. A well-defined microstructure composed of 5 microm x 25 microm rectangular features was successfully fabricated on a MPEOPS monolayer surface. Subsequently treated it by spatially defined CVD treatment using aminosilane molecule, binary microstructures composed of PEG and amino-terminated surfaces were successfully fabricated.
authors.affiliation: International Center for Young Scientists, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Shirahata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hozumi
mesh_terms: D000327:Adsorption; D006046:Gold / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D036103:Nanotechnology / Q000379:methods*; D010777:Photochemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry; D012825:Silicon / Q000737:chemistry*; D013057:Spectrum Analysis; D013499:Surface Properties; D014965:X-Rays
chemical_list: D012821:Silanes; D011092:Polyethylene Glycols; D006046:Gold; D012825:Silicon