IN-SITU STUDY OF POLY(METHYL METHACRYLATE) ADSORPTION FROM SOLUTION ONTO CHEMICALLY-MODIFIED SI(100) SURFACES BY INTERNAL-REFLECTION INFRARED-SPECTROSCOPY

A liquid attenuated total reflection cell designed to accommodate in situ cleaning and/or chemical modification of Si(100) surfaces, has been employed to study the adsorption poly(methyl methacrylate) (PMMA) from solution. In situ cleaning of the substrate surface was accomplished by photochemical generation of ozone to produce a clean oxide film, while aqueous HF etching was carried out by introduction of an aqueous HF solution to produce a hydrogen terminated silicon surface (silicon hydride). The in situ cell allowed for observation of infrared bands from the polymer adsorbate, as well as the silicon substrate surface during the course of polymer adsorption. The fraction of PMMA segments with the carbonyl groups hydrogen bonded to the silanol sites on the silicon substrate was 0.25-0.29 on the clean oxide surface and 0.09-0.13 on the hydrogen terminated surface. For the highly contaminated, ''as-received'' native oxide surface, no hydrogen bonding was detected, although PMMA was found to adsorb. The integrated carbonyl intensities indicate that the relative amount of polymer adsorbed onto the ultraviolet/ozone cleaned and HF etched surfaces was significantly greater than the contaminated surface. The Si-H stretching band decreased during the adsorption on the hydrogen terminated surface, suggesting that some oxidation of the HF etched surface occurred during 12 h in the PMMA-CCl4 Medium. Even so, 90% of the Si-H intensity is retained in that experiment.