VAMAS interlaboratory study on organic depth profiling

Abstract

We present the results of a VAMAS (Versailles project on Advanced Materials and Standards) interlaboratory study on organic depth profiling, in which twenty laboratories submitted data from a multilayer organic reference material. Individual layers were identified using a range of different sputtering species (C 60 n+ , Cs + , SF 5 + and Xe + ), but in this study only the C 60 n+ ions were able to provide truly 'molecular' depth profiles from the reference samples. The repeatability of profiles carried out on three separate days by participants was shown to be excellent, with a number of laboratories obtaining better than 5% RSD (relative standard deviation) in depth resolution and sputtering yield, and better than 10% RSD in relative secondary ion intensities. Comparability between laboratories was also good in terms of depth resolution and sputtering yield, allowing useful relationships to be found between ion energy, sputtering yield and depth resolution. The study has shown that organic depth profiling results can, with care, be compared on a day-to-day basis and between laboratories. The study has also validated three approaches that significantly improve the quality of organic depth profiling: sample cooling, sample rotation and grazing angles of ion incidence.

VAMAS interlaboratory study on organic depth profiling. Part I: Preliminary report

“…The protocol for analysis [2] was sent to all participants. This provided guidance on measuring the sputter beam diameter and setting the sputter and analysis areas to ensure a constant ion dose across the analysis area.…”

Improved mass resolution and mass accuracy in TOF-SIMS spectra and images using argon gas cluster ion beams

“…Irganox V R 1010 was selected for external mass calibration [29][30][31][32] because this organic material is inexpensive and commonly used to evaluate the performance of cluster ion beams through depth profiling. [7][8][9] Further, positive and negative spectra that contain well-known multiple characteristic and molecular peaks from the low-to the high-mass spectral regions (up to m/z 1200) can be obtained from this material in a reasonable time (less than 10 s). Figures 2(a) and 2(b) are positive and negative spectra obtained by using Ar-GCIB in the delayed ion extraction mode.…”

“…According to computer simulations 1 and experimental [2][3][4][5][6] reports, the ejection of high mass secondary ions is enhanced with the nonlinear effects of multiple collisions when large-sized cluster ion beams bombard the organic surfaces. There are some reports that a cluster ion beam as the sputtering ion source can successfully accomplish depth profiling of organic [7][8][9][10] and amino acid films 11 without ion damage. For example, Mochiji and Oshima et al used argon gas cluster ion beams (Ar-GCIB) to measure several peptides and proteins with molecular weights of up to 15 kDa such as insulin, cytochrome C, lysozyme, and chymotrypsin, which were previously undetected in TOF-SIMS using atomic ion beams.…”

Molecular Depth Profiling with Cluster Ion Beams

“…is observed. 39,11,23,25,28,33,81,85 Furthermore, increased fragmentation and beam damage effects (initial signal decay/damage cross sections) are observed in the mass spectral data at higher beam energies. 39,23,26,28,33,95 -97 Finally, XPS results are also consistent with increased structural damage at higher beam energies.…”