Sergio L. A. Mello oral presentation (PB1-Mon2-1-4)
Development of a SIMS system using a MV tandem accelerator as a spectrometer
1 Departamento de Física, Universidade Federal de Viçosa, Av. PH Rolfs, 36570-900 Viçosa, Brazil
2 Instituto de Física, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 21941-972 Rio de Janeiro, Brazil
In this work we describe the development of a secondary ion mass spectrometry (SIMS) system using a tandem accelerator equipped with a source of negative ions by cesium sputtering (SNICS). The sample is mounted in the SNICS ion source, at the cathode position, and is bombarded with Cs+ beam. The energy and intensity of this primary beam is controlled by the cathode voltage and the ionizer current, respectively. Part of the particles sputtered from the sample become negatively charged. These negative ions form the secondary ion beam which travels through the accelerator and is detected on a metallic plate in one of the beamlines. The identification of beam species is obtained with a homemade automated system written in the LabVIEW programming environment. The code is used to vary the electric field intensity of a crossed ExB-based mass analyzer, located between the ion source and the accelerator tank, while performing current measurements that are proportional to the secondary ion beam intensity. A complete sweep takes from tens of seconds to a few minutes, depending on the voltage step, to generate a mass spectrum. Analysis of the surface evolution can be obtained by successive mass spectra measured in this way.
We discuss some advantages of having a SIMS system in combination with a tandem accelerator. One of them, for instance, is to pass from static to dynamic SIMS, by simply adjusting the parameters of the primary ion beam in the ion source rack. Examples of SIMS measurements of thin films using our developed system are given, and the limitation of the measurements are discussed.