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candidates are those which become fluid (rather than decomposing) under the conditions of TA-FAB. Several solids me currently being evaluated for use: citric acid, inositol, urea, oxalic acid, and ammonium chloride. Polymers shall also be investigated. Work in progress will delineate several indices of analytical merit such as sensitivity, precision, and dynamic range. Finally, a continuing objective will be to more clearly understand the phenomena responsible for the observed effects associated with this technique.
ACKNOWLEDGMENT The authors thank M. R. Davenport for his continued technical assistance in support of this research. Registry No. Fructose, 57-48-7; glucose, 50-99-7;tartaric acid, 87-69-4; thiamin hydrochloride, 67-03-8; alanyl-leucyl-glycine, 60030-20-8; L-arginine, 74-79-3;ampicillin, 69-53-4; sodium taurodeoxycholate, 1180-95-6.
LITERATURE CITED (1) Beckey, H. K. Int. J. Mass Spectrom. Ion Phys. 1969, 2, 500. (2) Torgerson, D. F.; Skowronski, R. P.; Macfarlane, R. D. Blophys. Res. Common. 1974, 60, 616. (3) Grade, H.; Wlnograd, N.; Cooks, R. G. J. Am. Chem. SOC. 1977, 99, 7725. (4) Posthumus, M. A.; Kistemaker, P. A,; Meuzelaar, H. Anal. Chem. 1978, 50, 985. (5) Barber, M.; Bordoli, R. S.; Sedgwick, R. D.; Tyler, A. N. J. Chem. Soc.. Chem. Commun. 1981, 325. (6) Devienne, F. M.; Roustan, J. C.; C . R. Hebd. Seances Aced. Sci., Ser. 6 1976, 283, 397. (7) Benninghoven, A,; Jaspers, D.; Sichtermann, W. Appl. Phys. 1978, 11,35.
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(8) Barber, M.; Bordoli, R. S.; Sedgwick, R. D.; Tyler, A. N.; Elliott, 0. J. Anal. Chem. 1982, 5 4 , 645A. (9) Ackermann, B. L.; Watson, J. T.; Newton, J. F., Jr.; Hook, J. B.; Braselton, W. E., Jr. 6lomed. Mass Spectrom. 1984, 1 1 , 502. (IO) Gilliam, J. M.; Landis, P. W.; Occolowitz, J. L. Anal. Chem. 1983, 55, 1531. (11) Yost, R. A,; Fetterolf, D. D. Mass Spectrom. Rev. 1983, 2, 1. (12) Martin, S. A.; Costello, C. E.; Biemann, K. Anal. Chem. 1982. 54, 2362. (13) Maine, J. W.; Soltmann, B.; Holland, J. F.; Young, N. D.; Gerber, J. N.; Sweeiey, C. C. Anal. Chem. 1976, 4 8 , 427. (14) Friedman, L.; Beuhler, R. J. 26th Annual Conference on Mass Spectrometry and Allied Topics, St. Louis, 1978; Workshop on Field Desorption. (15) Busch, K. L.; Hsu, B. H.; Xle, Y.; Cooks, R. G. Anal. Chem. 1983, 55, 1157. (16) Hardin, E. D ' Fan, T. P.; Vestal, M. L. Proceedings of the 32nd Annual Conferencejbn Mass Spectrometry and Aiiied Topics, San Antonio, TX, 1984, 246. (17) Glish, G. L.; Todd, P. J.; Busch, K. L.; Cooks, R. G. Int. J. Mass Spectrom. Ion Proc. 1984, 56, 177-192. (18) Barber, M.; Bordoli, R. S . ; Sedgwlck, R. D.; Tetler, L. W. Org. Mass Spectrom. 1981, 16, 258. (19) Germain, P.; Prome, J. C. Org. Mass Spectrom. 1984, 19, 448. (20) Meili, J.; Seibi, J. Org. Mass Spectrom. 1984, 19, 561. (21) Busch, K. L.; Unger, S. E.; Vincze, A.; Cooks,%. G.; Keough, T. J. Am. Chem. SOC. 1982, 104, 1507. (22) Morris, H. R.; Dell, A.; Etienne, A. T.; Judkins, M.; McDonell, R. A.; Panico, M.;Taylor, 0. W. Pure Appl. Chem. 1982, 5 4 , 267.
RECEIVED for review March 14, 1985. Accepted July 5,1985. This work was supported by the Biotechnology Research Program under the Division of Research Resources of the National Institutes of Health (NIH Grant No. RR00480-16). In addition, B. L. Ackermann received support from the Dow Chemical Co. in the form of a research fellowship.
On-Line Ion Implantation for Quantification in Secondary Ion Mass Spectrometry: Determination of Trace Carbon in Thin Layers of Silicon Howard E. Smith and George H. Morrison*
Department of Chemistry, Cornel1 University, Ithaca, New York 14853
The duopiasmatron ion source of the Cameca IMS 3f secondary Ion mass spectrometer has been used to generate a mass-filtered ion beam for the purpose of Implanting an internal standard Into a semiconductor matrlx. Depth profile analyses of C+ Implants superimposed upon residual C concentrations In a 5800-A film of polycrystalllne Si have shown that unlform, accurate doses of primary Ions can be implanted. Residual C concentrations, determined from nine such on-line Ion Implant analyses, gave values of 3.4 (f0.4) X 10'' atoms/cm3. This value agreed accurately wlth an off-line Ion implant concentratlon determination, wlth a relatlve dlfference of -8 %. This technlque extends the quantltatlve capablllties of the Ion mlcroanalyzer.
Secondary ion mass spectrometry (SIMS) offers high sensitivity for the detection of most elements, high dynamic range, and excellent depth resolution (50-100 A). Hence, it is an excellent technique for quantitative elemental depth profiling analysis. In empirical quantification, the signal level from a known concentration of an external standard is used to obtain the analytical curve or sensitivity factor (1). The variability in sputtering yields and practical ion yields observed in sam0003-2700/85/0357-2663$0 1.50/0
ples of different matrices places several restrictions on the analysis. The matrix of the standard must be identical or nearly identical to that of the analyte of interest. The standard and the analyte samples must be analyzed under the same instrumental and experimental conditions. Any variation in the experimental conditions that takes place during the analyses can be corrected for by referencing the analyte signal level to that of an internal reference element, usually a matrix signal. This method is known as the relative sensitivity factor (RSF) method. The method assumes that the analyte and reference signals will be affected in the same way by changes in the experimental conditions. The method of solid-state internal standard addition elegantly circumvents the matrix-effect problem. Ion implantation is used to superimpose a quantification standard upon a homogeneously distributed analyte: typically, a mass-filtered ion beam is accelerated to 50-300 keV and rastered uniformly over the surface of the sample. The ions are stopped in the sample as atoms with a distribution that approximates that of a Gaussian (2). Subsequent depth profiling of this additive distribution, and the ratio of the integrated signals from each, gives a measurement of the volume concentration of the residual analyte, if the depth of analysis and the implanted fluence are known. The methodology and requirements for 0 1985 American Chemical Society
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such a determination have been previously described in detail (3-5). This study describes the first use of the SIMS primary ion beam for implanting an internal standard into a sample, to obtain an immediate empirical on-line quantification that uses the same methodology as is used for externally implanted samples. As such, the problems of prohibitive expense, limited availability, and time delay associated with implantation facilities can be circumvented. It is therefore possible to determine concentrations of analyte (
