Surface potential microscopy for chemistry of organic self-assembled monolayers in small domains

Abstract

Micropatterning techniques using vacuum ultra-violet light at 172 nm in wavelength and an ultra-violet laser at 244 nm were applied to organosilane self-assembled monolayers (SAMs) formed on Si substrates covered with a 2 nm thick oxide layer. These SAMs were prepared from precursors, that is, octadecyltrimethoxysilane (ODS) or p-chloromethylphenyltrimethoxysilane (CMPhS). Polar functional groups such as COOH were generated through photochemical oxidation of the SAMs. Furthermore, the SAMs were simultaneously etched and finally removed from the photoirradiated area. Surface potentials of the photoirradiated areas at various irradiation dose rates were measured by Kelvin-probe force microscopy (KFM) using the unirradiated area on each of the photopatterned samples as a reference. Changes in the surface chemical composition of the SAMs could be clearly and sensitively measured by KFM through the difference in surface potential between the irradiated and unirradiated SAMs.