On the understanding and the optimization of ToF-SIMS depth profiles by cosputtering cesium and xenon

In this work, the ToF-SIMS depth profiles of a gold layer deposited on a bare silicon wafer were studied by cosputtering cesium and xenon. Firstly, a pure cesium depth profile was measured and the transient region at the interface between the gold layer and the silicon substrate was investigated. Secondly, several depth profiles of the Au layer were performed with varying cesium beam concentrations and the intensities of the positive signals (i.e. Au, Si, CsAu, CsSi, Cs, etc.) were monitored. The intensities of the signals were plotted with respect to the cesium surface concentration and were modeled according to the tunneling model. The study of these curves permitted us to understand and to optimize the ToF-SIMS depth profile of the Au/Si system.