Laser-Induced Chemistry and Desorption of Organic Monolayers

Abstract

Laser-induced desorption of organic monolayers (LIDOM) is performed to analyze the chemical nature, thermal stability, and fragmentation pattern of organic silicon terminations based on calibration of surface heating introduced with a XeCl laser (308 nm). Results are presented for trimethylsilyl- (TMS) and 1-norbornen-2-yl(ethyl)dimethylsilyl- (NDMS) terminated surfaces which were prepared by silanization with suitable chloro compounds. Depending on laser fluence, either essentially intact end groups are emitted from the surface or specific fragmentation patterns are generated preferentially at higher energy densities. Clean retro Diels−Alder cleavage (rDA) was initiated in a norbonen compound at low fluences (110−200 mJ/cm2), providing reactive surface moieties such as double bonds that can be used as a starting point for controlled secondary surface reactions. At fluences above 200 mJ/cm2 fragmentation of the NDMS group takes place.