Ion Beam Centre’s research to feature in Royal Society of Chemistry collection
The paper demonstrates that the classical method of Rutherford backscattering spectrometry (RBS) really can be used as a primary direct reference method for measuring Quantity of Material in thin films. The method is reference-free, and makes no assumptions about the sample, that is, it is self-validating. RBS is “non-destructive”, that is, the sample is not significantly changed unless the energy deposited by the beam causes changes (such as cross-linking in polymers or other beam-damage effects).
The Ion Beam Centre is a world leader in ion implantation research: ion implantation is an enabling technology for the huge semiconductor industry world-wide. This work summarises the quality assurance method we use for certifying the implantation fluence, obtaining absolute accuracies approaching 1%. This is done directly for test implants, without the system calibration required for industrial implanters.
The work depends on accurate determination of the electronic gain of the spectrometric system (Analytical Methods 2015) and of the energy loss behaviour of silicon (which is used as an internal reference: Analytical Methods 2014). The robustness of the method was first demonstrated in a multi-lab comparison (Analytical Chemistry 2012: Surrey, Budapest, Lisbon).
The beam energy is also obtained directly with very high accuracy, enabling absolute calibration of the terminal voltage of the accelerator (Nuclear Instruments & Methods B, 2015). This was also a multi-lab work (Surrey, Namur) which incidentally established the energy of the 7156 keV level of the 20Ne nucleus with a greatly reduced uncertainty.
In addition, the method is currently undergoing accreditation for ISO 17025 certification, which would be a first for any Ion Beam Analysis lab worldwide.
The work is the culmination of a series of five papers:
- C. Jeynes, N.P.Barradas, E. Szilágyi, Accurate determination of Quantity of Material in thin films by Rutherford backscattering spectrometry, Analytical Chemistry 84 (2012) 6061-6069
- J. L. Colaux and C. Jeynes, High accuracy traceable Rutherford backscattering spectrometry of ion implanted samples, Analytical Methods 6 (2014) 120-129
- J.L. Colaux, G. Terwagne, C. Jeynes, On the traceably accurate voltage calibration of electrostatic accelerators, Nuclear Instruments and Methods in Physics Research B, 349 (2015) 173–183
- Julien L. Colaux and Chris Jeynes, Accurate electronics calibration for particle backscattering spectrometry, Analytical Methods 7 (2015) 3096-3104
- Julien L. Colaux, Chris Jeynes, Keith C. Heasman and Russell M. Gwilliam, Certified ion implantation fluence by high accuracy RBS, Analyst, 140 (2015) 3251-3261