Monitoring of photodeposition of polymer films from diacetylene monomer solutions using in situ real-time spectroscopic ellipsometry

Abstract

Photodeposition of thin polymer (PDAMNA) films from diacetylene monomer (DAMNA) solutions onto 80 Å gold coated silica substrates with UV light was studied using the technique of in situ real-time spectroscopic ellipsometry. The dielectric function of the PDAMNA film was determined, and it reveals typical optical properties for organic materials in the photon energy range (1.6–2.7 eV). The thickness of a growing PDAMNA film over a 4-h time interval was determined using a linear regression fit of the experimental data to a homogeneous four phase optical model. The growth rate was observed to be essentially linear with time during the early stages of photodeposition, as expected. However, it was found that stirring the solution dramatically lowered the rate of film deposition. It is believed that fluid flow enhances transport of reactive species generated in the vicinity of the substrate away from the surface and into the bulk solution, where they become quenched. Lastly, the morphology of the PDAMNA film was examined using non-contact mode atomic force microscopy, indicating that the film contains embedded aggregates of precipitated polymer with diameters ranging from 20 to 100 nm. These results are consistent with those obtained previously using optical microscopy.