A tour around a typical ToF-SIMS instrument where NPL has developed the metrology. An example plot of the effect of secondary ion mass and energy on the detector efficiency is shown.

The use of Secondary Ion Mass Spectrometry (SIMS) is supported by a robust measurement infrastructure. Over the years NPL has developed metrology and provided guidance in these areas (1) Ion beam damage – a simple bond-breaking model was developed to describe the observed damage effects in organics [1]. (2) Electron beam damage – we showed a recommended upper limit of 6 x 10¹⁸ electrons/m² [2]. (3) Ion detection efficiency – the detector efficiency drops off rapidly for large secondary ions and depends strongly on the ion composition. Increasing the ion energy to 20 keV improves efficiency considerably, as illustrated above. [3] (4) Instrument repeatability – excellent repeatability of 1% is now typically realised, an improvement by 1 to 2 orders of magnitude through a series of VAMAS studies [4]. (5) Instrument reproducibility– the NPL RISR method improves spectral equivalence between different spectrometers by up to a factor of 33 [5]. (6) Calibration of the mass scale – our research evaluated the reasons behind the poor mass scale calibration and recommendations were provided to improve this by a factor of 10 [6]. (7) Sample topography – this can severely restrict analyses and guidance was given to diagnose and reduce topographical artefacts [8]. (8) Detector linearity – SIMS signal linearity is limited by single ion counting statistics. Factors affect linearity and the use of Poissonian intensity correction in practical analyses is discussed.

Selected Publications

[1] Static SIMS: a study of damage using polymers, I S Gilmore and M P Seah, Surf. Interface Anal., 24, 746 (1996).

[2] Electron flood gun damage in the analysis of polymers and organics in time of flight SIMS, I S Gilmore and M P Seah, Appl. Surf. Sci., 187, 89 (2002).

[3] Ion detection efficiency in SIMS: energy, mass and composition dependencies for microchannel plates used in mass spectrometers, I S Gilmore and M P Seah, Int. J. Mass Spectrom., 202, 217 (2000)

[4] Static SIMS – VAMAS interlaboratory study for intensity repeatability, mass scale accuracy and relative quantification, F M Green, J L S Lee, I S Gilmore, S J Spencer and M P Seah, Surf. Interface Anal., SIA 42 (2010) 129

[5] Static ToF-SIMS – A VAMAS interlaboratory study – Part I – Repeatability and reproducibility of spectra, I S Gilmore, M P Seah and F M Green, Surf. Interface Anal., 37, 651 (2005).

[6] ToF-SIMS: accurate mass scale calibration, F M Green, I S Gilmore and M P Seah, J. Am. Soc. Mass Spectrom. 17, 514 (2006)

[7] Topography and field effects in the quantitative analysis of conductive surfaces using ToF-SIMS, J L S Lee, I S Gilmore, I W Fletcher, M P Seah, Appl. Surf. Sci. 255 (2008) 1560–1563

Reference Guide

Development of a Standards Base for Static SIMS – A Review

If you require PDF copies of the publications, please contact us below.

Contact: Ian Gilmore