Fluorinated Silane Self-Assembled Monolayers as Resists for Patterning Indium Tin Oxide

Abstract

We report the formation of self-assembled monolayers (SAMs) on indium tin oxide (ITO) substrates with perfluoroorganosilanes in liquid and supercritical carbon dioxide and a method of patterning the monolayer that does not use any organic solvents. The monolayers formed were used as an etch resistant during the formation of patterns as small as 300 nm. The monolayers were characterized using wettability experiments, surface FT-IR, cyclic voltammetry, and AFM. The effects of temperature and adsorption time on the formation of SAMs were explored. Advancing contact angles as high as 105° and fractional surface coverages up to 0.96 were achieved by exposing the ITO surfaces to silanes in scCO2 for 15 h. Surface FT-IR results show peaks at 1212 and 1152 cm-1, typical for disordered monolayers. Yet, these SAMs are resistant to wet etching for over 10 h, indicating that dense carbon dioxide is a superior solvent for SAM formation of perfluorosilanes on ITO.