Positive SIMS (cation) spectrum dominated by electropositive atom ionsNegative SIMS (anion) spectrum dominated by electronegative atom ionsCharacteristics of SIMS spectra- small clusters abundant- no large clusters- no multiply-charged clusters- few multiply-charged ions- sensitive to isotopic abundance- often observe (K+), Na+, Cl-, F-Static SIMS used to "fingerprint" polymersStatic SIMS can also be used to study adsorbed molecules Change in ion yield at 250 K implies CO molecule dissociates to adsorbed O and C at this temperatureSSIMS ion yields dependent on "chemical environment" of surface atomsImages from SIMSObtained in two ways:(1) scan ion beam (raster) across surface - ion microprobe technique(2) scan ion collection optics across surface uniformly irradiated ion microscopy techniqueCan focus high energy ion beam to