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Nanocomposites, and in particular, Polymer-Fullerene blends, have recently drawn strong attention owing to their properties and their numerous applications in new-generation electronic and optoelectronic devices. The fullerene concentration in the material is critical since it dictates its electrical behavior, In this context, precise knowledge of the fullerene depth distribution in the blends is needed. Here, we investigate the capability of the ToF-SIMS technique to provide quantitative information on PMMA-C 60 blends with extremely small C 60 concentrations. Smooth PMMA layers of ~130 nm thickness ranging from 0 to 0.04 wt% C 60 were deposited on Si wafers. Samples were analyzed with an ION-TOF TOF SIMS V instrument in negative mode. Using low-energy Cs + sputtering (250 eV) and Bi 3 + as the analysis ion allowed monitoring of C 60 characteristic secondary ions, namely C 60 - and its isotopes at m = 720,721,722,723,724,725 u. Operating the beams in noninterlaced mode enabled successful depth profiling of samples with very little signal decay. Improvement of depth resolution was achieved by cooling the sample while profiling; AFM study of crater bottoms showed reduced roughness at lowtemperature, justifying the improvement. Segregation in depth of C 60 against PMMA was not observed, in agreement with surface free energy values determined by a contact angle method. Point-by-point normalization of C 60 signal (C 60 - , m = 720 u) to PMMA monomer signal (C 5 H 9 O 2 - , m = 101 u) was found to give a linear function of C 60 concentration with excellent regression coefficient. |
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