Quantization of secondary ion mass spectrometry (SIMS) data using external and internal standards

Some aspects of multi-dimensional characterization of solids by secondary ion mass spectrometry (SIMS) are given. A theoretical part discusses methods for the quantization of SIMS data and the most prominent effects of ion-solid interactions as related to SIMS. After a description of the instrument used for experiments (a quadrupole-equipped ion microprobe featuring a liquid metal ion source in addition to the standard duoplasmatron gas ion source) the first experimental section is devoted to the determination of practical sensitivities and relative sensitivity factors for selected pure elements, binary and treary alloys and multicomponent systems. For 23 pure elements practical sensitivities under O+2 bombardment also have been compared to those under In+-bombardment; it was shown that on oxygen saturated surfaces yields under In+-bombardment are higher, this making feasible use of submicron In-beams for surface analysis. In the second experimental section boron implants in silicon have been used for studying depth profiling capabilities of the instrument. Sputtering yields of Si and degrees of ionization of both B and Si have been measured. It has been shown that implantation profiles may deviate considerably from Gaussian but can be described by means of mathematical distribution functions. In the third experimental section depth resolution of the erosion process has been studied by profiling a Ni/Cr multilayer sample (100 A single layer) and been found to be approximately constant over the depth range investigated. Quantization of depth profiles, usually distorted by matrix effects, has been attempted using the primary beam species (In) as internal implantation standard. Some problems in connection with the conversion of secondary ion micrographs to concentration maps are discussed. Elemental detection limits in multidimensional SIMS analysis are given in dependence of primary beam size and total eroded depth. (Author)