Secondary ion mass spectrometry

Secondary ion mass spectrometry (SIMS) is a tech-nique used to analyze the composition of solid surfacesand thin films by sputtering the surface of the specimenwith a focused primary ion beam and collecting and ana-lyzing ejected secondary ions. The mass/charge ratios ofthese secondary ions are measured with a mass spectrom-eter to determine the elemental, isotopic, or molecularcomposition of the surface to a depth of 1 to 2 nm. Dueto the large variation in ionization probabilities amongdifferent materials, SIMS is generally considered to bea qualitative technique, although quantitation is possiblewith the use of standards. SIMS is the most sensitive sur-face analysis technique, with elemental detection limitsranging from parts per million to parts per billion.

1 History

In 1910 British physicist J. J. Thomson observed a re-lease of positive ions and neutral atoms from a solid sur-face induced by ion bombardment.[1] Improved vacuumpump technology in the 1940s enabled the first proto-type experiments on SIMS by Herzog and Viehbck[2]in 1949, at the University of Vienna, Austria. In themid-1950s Honig constructed a SIMS instrument at RCALaboratories in Princeton, New Jersey.[3] Then in theearly 1960s two SIMS instruments were developed inde-pendently. One was an American project, led by Liebeland Herzog, which was sponsored by NASA at GCACorp, Massachusetts, for analyzing moon rocks,[4] theother at the University of Paris-Sud in Orsay by R. Cas-taing for the PhD thesis of G. Slodzian.[5] These firstinstruments were based on a magnetic double focusingsector field mass spectrometer and used argon for theprimary beam ions. In the 1970s, K. Wittmaack andC. Magee developed SIMS instruments equipped withquadrupole mass analyzers.[6][7] Around the same time,A. Benninghoven introduced the method of static SIMS,where the primary ion current density is so small that onlya negligible fraction (typically 1%) of the first surfacelayer is necessary for surface analysis.[8] SIMS was de-veloped in the 1960s by the French company CAMECAS.A.S and used in materials science and surface sci-ence. Instruments of this type use pulsed primary ionsources and time-of-flight mass spectrometers and weredeveloped by Benninghoven, Niehuis and Steffens at theUniversity of Mnster, Germany and also by CharlesEvans & Associates. Recent developments are focusingon novel primary ion species like C60+, ionized clustersof gold and bismuth,[9] or large gas cluster ion beams

(e.g., Ar700+).[10] The sensitive high resolution ion mi-croprobe (SHRIMP) is a large-diameter, double-focusingSIMS sector instrument produced byAustralian ScientificInstruments in Canberra, Australia.

2 Instrumentation

Schematic of a typical dynamic SIMS instrument. High energy(usually several keV) ions are supplied by an ion gun (1 or 2) andfocused on to the target sample (3), which ionizes and sputterssome atoms off the surface (4). These secondary ions are thencollected by ion lenses (5) and filtered according to atomic mass(6), then projected onto an electron multiplier (7, top), Faradaycup (7, bottom), or CCD screen (8).

Typically, a secondary ion mass spectrometer consists of:

primary ion gun generating the primary ion beam

primary ion column, accelerating and focusing thebeam onto the sample (and in some devices an op-portunity to separate the primary ion species byWien filter or to pulse the beam)

high vacuum sample chamber holding the sampleand the secondary ion extraction lens

mass analyser separating the ions according to theirmass to charge ratio

ion detection unit.

1

https://en.wikipedia.org/wiki/Thin_filmhttps://en.wikipedia.org/wiki/Sputteringhttps://en.wikipedia.org/wiki/Ion_beamhttps://en.wikipedia.org/wiki/Mass_spectrometryhttps://en.wikipedia.org/wiki/Mass_spectrometryhttps://en.wikipedia.org/wiki/J._J._Thomsonhttps://en.wikipedia.org/wiki/Vacuum_pumphttps://en.wikipedia.org/wiki/Vacuum_pumphttps://en.wikipedia.org/wiki/University_of_Viennahttps://en.wikipedia.org/wiki/NASAhttps://en.wikipedia.org/wiki/Moon_rockhttps://en.wikipedia.org/wiki/Paris-Sud_11_Universityhttps://en.wikipedia.org/wiki/Sector_instrumenthttps://en.wikipedia.org/wiki/Quadrupole_mass_analyzerhttps://en.wikipedia.org/wiki/Static_secondary-ion_mass_spectrometryhttps://en.wikipedia.org/wiki/Camecahttps://en.wikipedia.org/wiki/Camecahttps://en.wikipedia.org/wiki/Materials_sciencehttps://en.wikipedia.org/wiki/Surface_sciencehttps://en.wikipedia.org/wiki/Surface_sciencehttps://en.wikipedia.org/wiki/Time-of-flight_mass_spectrometryhttps://en.wikipedia.org/wiki/University_of_M%C3%BCnsterhttps://en.wikipedia.org/wiki/Germanyhttps://en.wikipedia.org/wiki/Buckminsterfullerenehttps://en.wikipedia.org/wiki/Goldhttps://en.wikipedia.org/wiki/Bismuthhttps://en.wikipedia.org/wiki/Sensitive_high_resolution_ion_microprobehttps://en.wikipedia.org/wiki/Sensitive_high_resolution_ion_microprobehttps://en.wikipedia.org/wiki/Sector_instrumenthttps://en.wikipedia.org/wiki/Canberra,_Australiahttps://en.wikipedia.org/wiki/Ion_gunhttps://en.wikipedia.org/wiki/Ion_beamhttps://en.wikipedia.org/wiki/Wien_filterhttps://en.wikipedia.org/wiki/Vacuum

2 4 STATIC AND DYNAMIC MODES

2.1 Vacuum

SIMS requires a high vacuum with pressures below 104Pa (roughly 106 mbar or torr). This is needed to ensurethat secondary ions do not collide with background gaseson their way to the detector (i.e. the mean free path of gasmolecules within the detector must be large compared tothe size of the instrument), and it also prevents surfacecontamination by adsorption of background gas particlesduring measurement.

2.2 Primary ion sources

Three basic types of ion guns are employed. In one,ions of gaseous elements are usually generated withduoplasmatrons or by electron ionization, for instancenoble gases (40Ar+, Xe+), oxygen (16O-, 16O2+, 16O2-),or even ionized molecules such as SF5+ (generated fromSF6) or C60+ (fullerene). This type of ion gun is easy tooperate and generates roughly focused but high currention beams. A second source type, the surface ionizationsource, generates 133Cs+ primary ions.[11] Cesium atomsvaporize through a porous tungsten plug and are ionizedduring evaporation. Depending on the gun design, fine fo-cus or high current can be obtained. A third source type,the liquid metal ion gun (LMIG), operates with metalsor metallic alloys, which are liquid at room temperatureor slightly above. The liquid metal covers a tungsten tipand emits ions under influence of an intense electric field.While a gallium source is able to operate with elemen-tal gallium, recently developed sources for gold, indiumand bismuth use alloys which lower their melting points.The LMIG provides a tightly focused ion beam (

3

5 Applications

The COSIMA instrument onboard Rosetta will bethe first instrument to determine the composition ofcometary dust in situ with secondary ion mass spectrom-etry in 2014.[14]

6 References

[1] Thomson, J. J (1910). Rays of positive electricity. Phil.Mag. 20: 752767. doi:10.1080/14786441008636962.

[2] Herzog, R. F. K., Viehboeck, F (1949). Ionsource for mass spectrography. Phys. Rev. 76(6): 855856. Bibcode:1949PhRv...76..855H.doi:10.1103/PhysRev.76.855.

[3] Honig, R. E. (1958). Sputtering of surfaces by positiveion beams of low energy. J. Appl. Phys. 29: 549555.Bibcode:1958JAP....29..549H. doi:10.1063/1.1723219.

[4] Liebl, H. J (1967). Ion microprobe mass ana-lyzer. J. Appl. Phys. 38 (13): 52775280.Bibcode:1967JAP....38.5277L. doi:10.1063/1.1709314.

[5] Castaing, R. & Slodzian, G. J (1962). Optiquecorpusculairepremiers essais de microanalyse par emis-sion ionique secondaire. Microscopie 1: 395399.

[6] Wittmaack, K. (1975). Pre-equilibrium variation of sec-ondary ion yield. Int. J. Mass Spectrom. Ion Phys. 17:3950. doi:10.1016/0020-7381(75)80005-2.

[7] Magee, C. W. et al. (1978). Secondary ionquadrupole mass spectrometer for depth profiling de-sign and performance evaluation. Rev. Scient. In-strum. 49 (4): 477485. Bibcode:1978RScI...49..477M.doi:10.1063/1.1135438. PMID 18699129.

[8] Benninghoven, A (1969). Analysis of sub-monolayerson silver by secondary ion emission. Physica Status So-lidi 34 (2): K169171. Bibcode:1969PSSBR..34..169B.doi:10.1002/pssb.19690340267.

[9] S.Hofmann (2004). Sputter-depth profiling for thin-film analysis. Phil. Trans. R. Soc. Lond. A362 (1814): 5575. Bibcode:2004RSPTA.362...55H.doi:10.1098/rsta.2003.1304. PMID 15306276.

[10] S. Ninomiya, K. Ichiki, H. Yamada, Y. Nakata, T. Seki, T.Aoki, J. Matsuo (2009). Precise and fast secondary ionmass spectrometry depth profiling of polymer materialswith large Ar cluster ion beams. Rapid Commun. MassSpectrom. 23: 16011606. doi:10.1002/rcm.4046.

[11] Cesium Ion Gun System for CAMECA SIMS Units.http://www.peabody-scientific.com/. Retrieved 8November 2013.

[12] SIMS Detection Limits of Selected Elements in Si andSiO2 Under Normal Depth Profiling Conditions. EvansAnalytical Group. May 4, 2007. Retrieved 2007-11-22.

[13] Kaufman, A.J.; Xiao, S. (2003). High CO2 levels inthe Proterozoic atmosphere estimated from analyses ofindividual microfossils. Nature 425 (6955): 279282.doi:10.1038/nature01902. PMID 13679912.

[14] C. Engrand, J. Kissel, F. R. Krueger, P. Martin, J. Siln,L. Thirkell, R. Thomas, K. Varmuza (2006). Chemo-metric evaluation of time-of-flight secondary ion massspectrometry data of minerals in the frame of future insitu analyses of cometarys material by COSIMA onboardROSETTA. Rapid Communications in Mass Spectrome-try 20 (8): 13611368. doi:10.1002/rcm.2448. PMID16555371.

7 Bibliography Benninghoven, A., Rdenauer, F. G., Werner, H.W., Secondary Ion Mass Spectrometry: BasicConcepts, Instrumental Aspects, Applications, andTrends, Wiley, New York, 1987 (1227 pages)ISBN 0-471-51945-6

Vickerman, J. C., Brown, A., Reed, N. M., Sec-ondary Ion Mass Spectrometry: Principles and Ap-plications, Clarendon Press, Oxford, 1989 (341pages) ISBN 0-19-855625-X

Wilson, R. G., Stevie, F. A., Magee, C. W., Sec-ondary Ion Mass Spectrometry: A Practical Hand-book for Depth Profiling and Bulk Impurity Anal-ysis, John Wiley & Sons, New York, 1989 ISBN0-471-51945-6

Vickerman, J. C., Briggs, D., ToF-SIMS: Sur-face Analysis by Mass Spectrometry, IM Publica-tions, Chichester UK and SurfaceSpectra, Manch-ester UK, 2001 (789 pages) ISBN 1-901019-03-9

Bubert, H., Jenett, H., Surface and Thin FilmAnal-ysis; A compendium of Principles, Instrumentation,and Applications, p. 86-121, Wiley-VCH, Wein-heim, Germany 2002 ISBN 3-527-30458-4

8 External links CAMECA - since 1960s up to date, french DynamicSIMS manufacturer.

Annual SIMS workshop - site includes a literaturedatabase.

Tutorial pages for SIMS theory and instrumentation

Time-of-Flight SIMS - tutorial slide presentation.

Presentation by Dr. Charles Magee A HistoricalPerspective of SIMS.

https://en.wikipedia.org/wiki/Rosetta_(spacecraft)https://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1080%252F14786441008636962https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/1949PhRv...76..855Hhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1103%252FPhysRev.76.855https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/1958JAP....29..549Hhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1063%252F1.1723219https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/1967JAP....38.5277Lhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1063%252F1.1709314https://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1016%252F0020-7381%252875%252980005-2https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/1978RScI...49..477Mhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1063%252F1.1135438https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pubmed/18699129https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/1969PSSBR..34..169Bhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1002%252Fpssb.19690340267https://en.wikipedia.org/wiki/Bibcodehttp://adsabs.harvard.edu/abs/2004RSPTA.362...55Hhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1098%252Frsta.2003.1304https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pubmed/15306276https://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1002%252Frcm.4046http://www.peabody-scientific.com/page14.htmlhttp://www.peabody-scientific.com/http://www.eaglabs.com/files/appnotes/AN339.pdfhttp://www.eaglabs.com/files/appnotes/AN339.pdfhttps://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1038%252Fnature01902https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pubmed/13679912https://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1002%252Frcm.2448https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pubmed/16555371https://en.wikipedia.org/wiki/Special:BookSources/0471519456https://en.wikipedia.org/wiki/Special:BookSources/019855625Xhttps://en.wikipedia.org/wiki/Special:BookSources/0471519456https://en.wikipedia.org/wiki/Special:BookSources/0471519456https://en.wikipedia.org/wiki/Special:BookSources/1901019039https://en.wikipedia.org/wiki/Special:BookSources/3527304584http://www.cameca.com/http://www.simsworkshop.org/http://www.simsworkshop.org/literature.htmhttp://www.simsworkshop.org/literature.htmhttp://www.eaglabs.com/training/tutorials/sims_theory_tutorial/index.phphttp://www.eaglabs.com/training/tutorials/sims_instrumentation_tutorial/http://www.eaglabs.com/publications/presentations/TOFSIMS/Presentation_Files/index.htmlhttp://www.eaglabs.com/publications/presentations/Historical_Magee_2005/Presentation_Files/index.htmlhttp://www.eaglabs.com/publications/presentations/Historical_Magee_2005/Presentation_Files/index.html

4 9 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

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