DSIMS depth profiling

DSIMS depth profiling is usually performed with Ot, Cs+ and sometimes Nj. Bombardment with these species increases the secondary-ion yield by several orders of magnitude, particularly at normal and near-normal ion beam incidence 1109-111). The introduction of reactive gases is nevertheless risky because adverse effects also exist. 

Dynamic secondary ion mass qrectrometry (DSIMS) and Rutherford back scattering (RBS) are techniques that can provide information about composition profiles in polymer films. Both techniques provide elemental sensitivity, but neither will provide chemical bonding information as NEXAFS does, since both techniques rely on mass differences as a contrast mechanism. The depth profile is obtained on the basis of elemental conq>osition profiles in the film. In... 

FIGURE 19.7 Depth profiles for a PS-PFACg diblock copolymer film (a) area fraction of peaks assignable to neutral, CF2 and COO carbons to the Cj spectrum by XPS with ion bombardment and (b) PFA-Cg weight fraction by XPS with Cgg ion bombardment and by DSIMS. Reprinted with permission from Reference 39. 

Molecular aggregation structure of the PS-PFACg diblock copolymer films along the normal direction to the surface was also examined by dynamic secondary ion mass spectrometry (DSIMS), which is a well-established tool for the depth profiling of polymer materials. The PFA weight fraction at the depth of z by DSIMS was given as follows. 

Dynamic SIMS has been used to measure polymer diffusion, e.g. interdiffusion in the PS/PPO system [205], SIMS depth profiling enables to reveal silica present at some 10 nm below the surface. DSIMS has also been used to measure the film thickness of perfluoro-polyether lubricant coated on magnetic recording media by determining the etching time to the underlying carbon overcoat layer [206],... 

Dynamic SIMS (DSIMS) operates under conditions designed to remove surface layers sequentially during the analysis. This is achieved by rastering a primary ion beam over the area of analytical interest and collecting the emitted secondary elemental or cluster ions in the MS system. The erosion rates can be controlled from a few nanometres per hour to several tens of micrometres. The technique provides high sensitivity, quantitative elemental information in the form of mass spectra, depth profiles, and two- and three-dimensional images. All elements in the periodic table can be detected with sensitivities in the parts per million to parts per billion range. 

SIMS is based on the emission of atomic and molecular particles (.secondary ions) from the surface of a solid under bombardment with primary particles (ions). Under DSIMS conditions, the erosion rate is of the order of mono-layers) per second and concentration depth profiling can be performed with high spectrometric sensitivity, in favorable cases down to the ppb level. The. sensitivity of SIMS is element dependent and varies from I ppb to 100 ppm. and the technique is therefore used for trace and ultratrace analysis. 

The SLD profiles obtained from neutron reflectivity were confirmed using dynamic scanning mass spectroscopy (DSIMS) to measure the fluorine concentration as a function of depth. As can be seen from Fig. 12c, the DSIMS data shows the same qualitative skin-core features as observed by neutron reflectivity [47]. 

DSIMS instruments, ToF instruments already offer better depth resolution, with atomic mixing effects reduced to almost a monolayer. Furthermore all elements of one polarity can be profiled simultaneously. 

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