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Quantification Techniques Under Dynamic SIMS 1

Secondary Ion Mass Spectrometer Start-Up. Quantification Techniques Under Dynamic SIMS 1. General Relationship. Project Overview. c(A) = fractional concentration of element A (# A /total#) Y tot = total sputter yield (total species sputtered/primary ion)

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Quantification Techniques Under Dynamic SIMS 1

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  1. Secondary Ion Mass Spectrometer Start-Up Quantification Techniques Under Dynamic SIMS1 • General Relationship Project Overview c(A) = fractional concentration of element A (#A/total#) Ytot = total sputter yield (total species sputtered/primary ion) Np = primary ion rate (ions/second) il = number of A atoms in molecule Ωl Nq(Ml) = detection rate of molecule Ωl with charge q (counts/second) fq(Ml) = instrumental transmission factor αq(Ml) = probability of charge state q for molecule Ωl Department of Chemical, Biological, and Environmental Engineering Analysis of SIMS technology, science and application. Start up of a desktop SIMS tool for CBEE professor Dr. Gregory Herman. Tool will help SHARP Labs with thin film research. Tool will also be used by future grad students of Dr. Herman. Tyler Roberts and Jared Sherr Faculty Sponsor: Dr. Gregory Herman • Calibration Curve Method MiniSIMS: The Chemical Microscope For a matrix element R with constant concentration, the ratio of detected currents of element A to element R in charge state q is a function of the fractional concentration of A at or near the surface. A calibration curve must be made for different matrix type (i.e., for different chemistries). The Millbrook MiniSIMS tool is a compact solution for surface, or near surface characterization of solids. Secondary Ion Mass Spectrometry Overview Turbomolecular pump • Relative Sensitivity Factors Quadrupole mass spec • SIMS is based on secondary ion emission and the mass analysis of charged particles from solid surfaces. • Sample is bombarded with a beam of charged particles with energies in the 1-25 keV range. These incoming particles are called primary ions. Common ion sources include gallium and bismuth. • Advantages • Ease of use • High throughput • Low cost2 • Disadvantages • 2-300 amu mass range • Lower mass resolution For low concentration of A, a calibration curve is approximately a straight line. The values of the relative sensitivity factors Sr of element A for different reference elements R in a particular matrix type can be found by standard testing. Loading chamber Gallium primary ion source Future Projects • These primary ions bombard the surface and break bonds up to 3 nm deep. This process is called sputtering. • These charged species are called secondary ions. Typically this ejected material has an energy of ~20 keV. Tool will analyze silicon carbide films from SHARP Labs. These films have applications in multijunction photovoltaics. Determine the composition and presence of hydrogen, and the number of bonded carbon atoms in these thin films. The MiniSIMS may be used to assess surface contamination or differences in treatments3. It has been used to evaluate laser cleaning of museum objects4, study the structural properties of CuInSe2-based absorber layers for photovoltaics5, and monitor the effects of pre-treatment for adhesives2. Acknowledgements • Dr. Philip Harding • Millbrook • Dr. Greg Herman • Hewlett – Packard • University of Oregon • Static SIMS mode • Used for acquiring a mass spectrum • Low primary ion dose – least destructive • Answers the question, “what is present at the surface?” • Time of flight (TOF) relies on analyzing the time it takes for charged species to reach a detector. • Quadrupole mass spectroscopy (QMS) which relies on magnetic fields to filter particles of different masses. • Imaging SIMS mode • Used for acquiring a “chemical map” • Only one atomic mass unit considered at a time • Answers the question, “where on the surface are these chemical species located?” References • Dynamic SIMS mode • Used to acquire a depth profile • High primary ion dose – sputtering down into sample, very destructive • Answers the question, “how do these species compare to each other as a function of depth?” [1] Benninghoven, A, F.G. Rudenauer, and H.W. Werner. Secondary Ion Mass Spectrometry: Basic Concepts, instrumental Aspects, Applications and Trends. John Wiley & Sons: New York. 1987. [2] Eccels, A.J. and T.A. Steele. Routine problem solving with the SIMS chemical microscope. International Journal of Adhesion & Adhesives, 21 (2001), pages 281-286. [3] Eccles, A.J., T.A. Steele, and A.W. Robinson. Broadening the horizons of SIMS: the low cost Chemical Microscope. Applied Surface Science, 144(1999), pages 106-112. [4] McPhail, D.S., et.al. Rapid characterization of surface modifications and treatments using a benchtop SIMS instrument. Applied Surface Science, 231 (2004), pages 967-971. [5] Dale, P.J., et.al. Characterization of CuInSe2 material and devices. Journal of Physics D: Applied Physics, 41 (2008).

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