SIMS of organic layers with unknown matrix parameters: Locating the interface in dual beam argon gas cluster depth profiles

Abstract

Four simple methods are evaluated to determine their accuracies for establishing the interface location in secondary ion mass spectrometry intensity depth profiles of organic layers where matrix effects have not been measured. Accurate location requires the separate measurement of each ion's matrix factor. This is often not possible, and so estimates using matrix‐less methods are required. Six pure organic material interfaces are measured using many secondary ions to compare their locations from the four methods with those from full evaluation with matrix terms. For different secondary ions, matrix effects cause the apparent interface positions to vary over 20 nm. The shifts in the intensity profiles on going from a layer of P into a layer of Q are in the opposite direction to that for going from Q into P, so doubling layer thickness errors. The four methods are as follows: M1, use of the median interface position in the intensity profiles for the five lightest ions for 15 ≤ m/z ≤ 150; M2, extrapolation of the position for each ion to m/z = 0 for ions with m/z ≤ 150; M3, as M2 but for m/z ≤ 300; and M4, the extreme positions for all m/z ≤ 100. Comparison with the location using matrix terms shows their ranking, from best to worst, to be M4, M3, M1, and M2 with average errors of 10%, 12%, 14%, and 17%, respectively, of the profile interface full widths at half maximum. Use of pseudo‐molecular ions is very much poorer, exceeding 50%, and should be avoided.

Characterization of polymeric surfaces and interfaces using time‐of‐flight secondary ion mass spectrometry

“…A variety of polyatomic ions have been tested and implemented for depth profiling of soft materials, including SF 5 + and C 60 2+ , 29,30 and large argon clusters have emerged as the best for quantitative depth profiling of soft materials 24,26 . The argon gas cluster ion source offers the possibility to tune the cluster size and the energy‐per‐atom ratio for improving the secondary ion signal intensity and depth resolution, 24,31–34 and these are now available in commercial ToF‐SIMS systems. Terlier et al compared the performance of Cs + , C 60 2+ , and Ar 1500 + in performing depth profiling analysis of an aligned block copolymer film in a cylindrical morphology.…”

“…+ and C 60 2+ , 29,30 and large argon clusters have emerged as the best for quantitative depth profiling of soft materials. 24,26 The argon gas cluster ion source offers the possibility to tune the cluster size and the energy-per-atom ratio for improving the secondary ion signal intensity and depth resolution, 24,[31][32][33][34] and these Ar 1500 + in performing depth profiling analysis of an aligned block copolymer film in a cylindrical morphology. The authors found much more uniform depth profiling using the polyatomic cluster ions compared with Cs + .…”

A two‐point calibration method for quantifying organic binary mixtures using secondary ion mass spectrometry in the presence of matrix effects

“…6 This is of some importance when interpreting depth profile data in the case that the roughness component of the depth resolution is larger than the effective depth of mixing. 4 Data shown in a study with alternating layers 6 suggest that this effective depth of mixing where matrix effects are similar to intimate mixtures is less than 5 nm. Here, we have not dealt with methods to correct for compositional diversity in the analysis area and a more detailed knowledge of the character of the matrix effect than is provided by the calibration methods described here is required.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…One of the most common topics to receive research attention has been the analysis of copper-based alloys. An example of such an analysis was presented by Arnquist et al who reported the development of a method to determine 232 Th-and 238 U in copper using ICP-MS. 28 An automated, off-line matrix separation/analyte preconcentration method was developed in which the anion exchange resin AG 1X4 (100-200 mesh) was packed into a lowpressure chromatography system. This system was capable of cleaning the resin column, sample loading, matrix removal, analyte elution and collection with no input from the operator other than the initial programming.…”

“…Bellucci et al also used large geometry SIMS in combination with SEM to measure U and Pu isotopes simultaneously in a mixed hot particle recovered from the Thule accident in Greenland. 209 The particle was shown to have a single composition of weapons grade Pu, with the bulk of the particle having enriched U, with 235 U/ 238 U and 236 U/ 238 U ratios of 1.12 AE 0.04 and 0.006 AE 0.002, respectively. However, a small portion of the particle had 235 U/ 238 U and 236 U/ 238 U ratios of 0.11 AE 0.04 and 0.001 AE 0.002, respectively.…”