| Secondary Ion Mass Spectrometry was employed to examine polystyrene chain dynamics near attractive surfaces. Diffusion from a silicon surface and from a sputter-deposited carbon surface was compared in tri-layer sandwiches with a deuterated middle layer. The carbon surface serves as an analog for the carbon-black surface in nanocomposites. Strong segregation of the deuterated component was observed at the native silicon oxide surface, but was inhibited at the carbon surface. A finite element computer program was developed to fit the observed diffusion profiles. The diffusion coefficient D varies with depth superlinearly, scaling roughly as a 3/2-power. Importantly, D in the marker layer region is observed to decrease strongly with time at both the vacuum and solid wall surfaces.; The effect of standard wet chemical wafer cleaning procedures on the polystyrene/silicon interface was investigated as well. Deuterated solutions were employed to allow detection of remnant moisture from the cleaning/etching steps, and to indicate the extent of hydrogen termination at the polystyrene/silicon interface. The SIMS data indicated that the surface is effectively terminated by approximately one monolayer of hydrogen after an HF etch step, and by a thin oxide layer after an HCl/peroxide etch. The use of implant standards and a calibrated polymer blend permitted a rough calibration of the deuterium and fluorine concentrations at the interface. Also, deuterium and oxygen were found to be stable under high temperature anneals. The lack of a CD interfacial peak indicated that deuterium is associated with the silicon interface and not with the polymer chains. Oxygen and fluorine contamination peaks were also stable during the anneals. Following exposure to the peroxide/HCl solution, the deuterium level was shown to be much reduced, and the oxygen level is increased, as expected. Despite the wet processes employed in sample preparation, there is no evidence of remnant moisture in the interfacial region.; XPS and SIMS were also employed in studies of segregation, ordering, and surface bromination. |
