Negative Ion Sources - NIS

Coordinating Institution: CRP Gabriel Lippmann
Other Partner(s): CAMECA , Cératizit S.A. , Circuit Foil , Goodyear S.A.
From: 01/04/2006
To: 31/12/2008
Budget: 260,000.00€
Contact(s): Wirtz Tom

Summary

The NanoSIMS 50 has known an enormous success since its installation in Luxembourg in 2001 within the framework of the NANO programme. There remains however one major handicap becoming more and more severe on this instrument. As a matter of fact, the excellent lateral resolution, which this instrument is famous for, can only be reached when the Cs+ primary ion source is in use (thus while detecting negative secondary ions), as the duoplasmatron source is also available on the instrument, this does not by any means allow to have O - spot sizes compatible with the required NanoSIMS resolutions.

As a consequence, the NanoSIMS potential is not available for positive secondary ions. Important problematics encountered during the NANO projects in various fields of application (biology, medicine, materials science, …) cannot be solved nowadays on the NanoSIMS due to this lack of an adequate negative ion source.

This project aims at overcoming this handicap by developing a negative ion source compatible with the ambitious objectives of the NanoSIMS.

The general philosophy of this project consists in developing negative ion sources (I-, F-, Cl-, Br-, O-), the complete characterization of these sources on the dedicated SAM test bench and the use of these sources on a SIMS instrument (PhD thesis) in order to study the analytical sensitivities with respect to the different negative primary ions.

This project is part of the research work covered by the European Network of Excellence Nanobeams and it consequently profits from the expertise of Nanobeams.

Our efforts during 2008 allowed to develop a stable prototype of a surface ionization ion source. The source can be operated at high voltages of up to 10 kV, while keeping the ionizer at temperatures above 1000 °C. This development required a multitude of technological and scientific problems to be solved. The prototype source is now ready to be tested with different halogen ions in order to determine the brightness performances of the source.

In parallel, a duoplasmatron ion source has been operated and characterized with different gas mixtures to form O- and F- beams on a specially developed test bench. Similar protocols are currently being determined for the production of Cl- and I- ions.

The analytical study was started with an O- primary ion bombardment and is currently being extended to F- primary ions. As the PhD work focusing on this fundamental study only started in December 2006, it is continuing after the end of the FNR funded part of the NIS project.

Figure 1: Test bench dedicated to the characterization of ion sources and charged particle objects

Figure 2: View of the filament-wehnelt assembly which allows the ionizer of the prototype source to be heated to 1.000°C by electron bombardment.