An application of cesium-xenon co-sputtering: Quantitative study of a Pd-Rh thin film by ToF-SIMS

In this work, the ionization processes and the formation mechanisms of monoatomic and molecular ions were studied by co-sputtering cesium and xenon on a RhPd layer. Firstly, the relative concentrations of Rh and Pd and the thickness of the RhPd layer were measured by PIXE and by RBS, respectively. Secondly, the total sputtering yield was measured by ToF-SIMS for different cesium beam concentrations, varying from a pure xenon beam to a pure cesium beam. The sputtering yield was found to decrease linearly with cesium beam concentration, from 4.6 atoms/ion for the pure xenon to 4.0 atoms/ion for the pure cesium. The positive signals were then monitored with respect to the cesium surface concentration. As predicted by the tunneling model, the M signals decrease exponentially with the cesium surface concentration and the MCs yields exhibit a maximum for a well-defined Cs/Xe ratio.