SIMS Theory: Bulk Analysis

For samples with homogeneously dispersed analyte, bulk analysis provides better detection limits than depth profiling, usually by more than an order of magnitude. Faster sputter rates increase the secondary ion signal in bulk analysis. The fastest possible sputtering requires intense primary ion beams which sacrifice depth resolution because they cannot be focused as required for flat bottom (rastered) craters. Otherwise, bulk analyses are similar to depth profiles. Ion intensity data are displayed as a function of time. This provides a means for verifying that the sample is indeed homogenous. In a typical heterogeneous sample, the analyte is concentrated in small inclusions that produce spikes in the data stream.

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