DEPTH-PROFILING OF ORGANIC LAYERS ON MICROPARTICLES WITH SNMS

Previous work on the quanti cation and localization of organically bou nd elements with plasma-based SNMS for the characterization of micropa rticles has been continued. Relative detection factors for 10 elements have been determined. Except for lead and bromine a principle proport ionality to atomic ionization probabilities is shown. A moderate matri x dependence of less than 40% variation was found even when inorganic and organic materials are included. For depth calibration, erosion rat es of organic materials were determined from the time interval necessa ry to sputter through planar single-layers and Langmuir-Blodgett multi -layer systems with known thickness, as well as from gravimetric powde r measurements. Depth propagation rates were 0.7 nm . sec-1 for polyme rs and 2.3 nm . sec-1 for aromatic compounds, when 400 eV argon ion bo mbardment with 0.7 mA . cm-2 Was used. A depth resolution of approxima tely 30 nm has been obtained. Model particles of 5 mum size have been coated with fluoranthene. Inspection with SNMS revealed an incomplete coating covering only 20% of the microparticle surface with an average thickness of the partial coating of 300 nm. Subsequent characterizati on using laser-induced fluorimetry confirmed the amount of fluoranthen e coating measured by SNMS.