DEPTH PROFILING OF FUNCTIONALIZED SILANE FILMS ON QUARTZ AND SILICON SUBSTRATES AND OF UREASE IMMOBILIZED ON SUCH FILMS BY ANGLE-RESOLVED X-RAY PHOTOELECTRON-SPECTROSCOPY

The thickness of nonfunctional C-18, omega-carboxypentadecyl, and omeg a-aminododecanoylaminopropyl silane films covalently anchored on quart z and silicon substrates were evaluated by angle-resolved X-ray photoe lectron spectroscopy using an algorithm developed by Hill and co worke rs, making use of two sets of calculations. In one set, the ratio betw een the Si(2p) binding energy peak intensities of the silane overlayer and the substrate was utilized to compute the silane film thickness, and calculations used an experimentally determined normalization param eter. In the second set, the ratio between the intensities of the C(1s ) binding energy peak of the silane layer and the Si(2p) signal of the substrate was used along with an appropriate experimentally obtained normalization parameter to calculate the silane layer thickness, A sim ilar pair of computations were applied to measure the thickness of ure ase layers covalently attached to the omega-carboxy and omega-amino fu nctionalized silane surfaces using N(1s) and Si(2p) binding energy pea k intensities and normalization parameters, Good correlation between t he theoretically estimated and experimentally obtained (by XPS and cor roborated by ellipsometry) thickness values was achieved. Both polymer izable and nonpolymerizable silanes gave monolayer level surface films under the experimental conditions employed. A difference in the ureas e layer thickness based on the length and structure of the alkyl chain of the silane was observed.