Surface Science Spectra (SSS) provides high-quality, peer-reviewed spectra from a wide range of techniques including spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), low-energy ion scattering (LEIS), ultraviolet-visible spectroscopy (UV-vis), and secondary ion mass spectrometry (SIMS). This enables researchers to submit data from new or previously published experiments that are then made available to the community as a reference, for comparison to their own data or for further data analysis and the development of new data analysis methods. The detailed instrumentation information included in SSS submissions also provides all the information required for others to repeat the data collection conditions in order to acquire similar data from comparable samples.

To assure that the data submitted are both carefully acquired and accurately analyzed, the SSS templates are very detailed and can sometimes be intimidating to fill out. SSS submissions require much more instrumentation and sample details than that are typically reported in other publications. In addition, since the SSS spectra are presented as reference and comparison datasets, it is of the utmost importance that the information is accurate. This can be particularly challenging for SIMS submissions because SIMS data analysis can be difficult. Proper SIMS data analysis requires accurate mass calibration, correct assignment of peak centroids, accounting for isotopic distributions, and verification of peak identities (whenever possible) (Ref. 1). This is further complicated by the fact that most SIMS instruments produce data with moderate mass resolving power (∼3000 to 10 000 m/Δm) and mass accuracy (∼20–65 ppm). Due to these limitations and the complexities of the SSS SIMS template, these guidelines are provided to help increase the probability of acceptance of your SIMS submission and reduce the number of potential revisions requested after submitting. These guidelines should be used together with the SIMS Blank Template Instructions on the SSS website. It is my hope as an associate editor of SSS that these instructions will help facilitate a successful submission of your SIMS data to SSS.

SSS only accepts SIMS positive ion and negative ion spectral data. Do not submit SIMS image or depth profile data. You can submit positive and negative ion data together in one submission; however, if the number of spectra becomes large, you will need to break the datasets into smaller groups and submit each set separately. This can include preparing separate submissions for positive and negative ion data or separate submissions for subgroups of materials (with the positive and negative ion data together). If you have a large number of spectra to submit, please contact the editor for advice on the best way to divide the submission. Limiting the size of each submission helps reduce the burden on our reviewers and also simplifies searching the SSS database for readers.

SSS accepts SIMS data from most sample types; however, the submitted data should be from reproducible, simple sample systems. Data from complex mixtures and complicated multicomponent samples will be considered on a case-by-case basis depending on whether the data can be considered generally reproducible and representative of the sample type. If you have questions about the suitability of your SIMS data for SSS, please ask the editor before submitting.

All data from samples of a given polarity for each submission should be calibrated using the same set of peaks. If this is not possible, then a clear explanation of why separate calibration sets were used should be included in the Introduction. Calibration sets should include a minimum of three peaks. The identity of all calibration peaks must be known for certain before being used. Note that adding a large number of peaks to a calibration set does not necessarily improve the calibration. Carefully choosing three or four known peaks from across the given mass range will provide a good calibration. Do not use noisy, low intensity peaks in the calibration set. All calibration peaks should be clearly defined, symmetrical peaks of known identity. Once calibrated, peaks for the same species on all spectra should overlap with minimal variation in the peak positions. If this is not the case, the calibration is wrong, and you will need to recheck the calibration and verify that the spectra overlap as expected before submitting to SSS (see Fig. 1).

FIG. 1.

Examples of poor (a) and acceptable (b) calibrations. In (a), a common low mass peak does not overlap for all samples. This suggests the calibration is incorrect as common peaks should overlap very closely. The spectrum in (b) shows a reasonable calibration where all peaks at this mass overlap for all samples.

FIG. 1.

Examples of poor (a) and acceptable (b) calibrations. In (a), a common low mass peak does not overlap for all samples. This suggests the calibration is incorrect as common peaks should overlap very closely. The spectrum in (b) shows a reasonable calibration where all peaks at this mass overlap for all samples.

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If possible, do not use asymmetrical peaks in the calibration. Always make sure that the peaks are calibrated using the correct centroid of the peak. The correct centroid is the point of maximum intensity of the peak. Note that some software defaults to placing the centroid at the center of mass of the peak. Using this definition of the centroid, especially with asymmetrical peaks, will result in an incorrect calibration where the peak centroid can be shifted from the point of maximum intensity. This can cause errors in peak identification.

Mass resolving power in SIMS is defined as the mass of the peak divided by the full width at half maximum (m/Δm) of the peak. Due to this definition, using higher mass peaks artificially inflates the resolution of the spectra. Please use a low mass peak (below m/z 100) when assessing the mass resolving power. Always use the same peak for measuring mass resolving power for all spectra within a given submission. This enables easy comparison of the relative quality of each spectrum. We recommend using m/z = 27 (C2H3+) for positive ion data and m/z = 25 (C2H) for negative ion spectra. These peaks show up in almost all spectra from all samples of the given polarity.

The purpose of SSS SIMS submissions is to provide high-quality reference and comparison spectra to the community. The purpose of the submissions is not to try and identify every peak in each spectrum. It is better to not identify a peak than to incorrectly identify a peak that then ends up in the literature. The individual Spectral Features Tables are for peaks unique to the given spectrum. If there are common peaks present in all submitted spectra, please put these in a spectral features table at the end of the submission.

Peak identification in SIMS spectra is challenging. Only submit peak identifications for high intensity peaks that are clearly defined and that meet the following criteria:

  • Peak identities should be based on the exact mass of the peak centroid (point of highest intensity), the isotopic pattern, and logic of the assignment.

  • Peak identities should match the centroid mass with an error less than ±65 ppm. Peaks with higher ppm errors will not be accepted.

  • Do not include peak identities for any peak where you are not certain of the identity. Identifying fewer peaks accurately is better than many peaks with uncertainty.

  • Do not include peak identities for peaks that overlap with potential isotopes of other peaks. Typical SIMS instruments do not have the resolution to resolve peaks that overlap isotopes.

  • Do not submit peak identities for any peak where the signal to noise is lower than 3× the background signal.

  • Do not submit peak identities for any noisy peak that does not have a clearly defined peak shape (see Fig. 2).

FIG. 2.

Example of a noisy peak. Though this peak shows signal greater than 3× the background, it does not have a clearly defined peak shape and is too noisy. This peak should not be included in the Spectral Features Table.

FIG. 2.

Example of a noisy peak. Though this peak shows signal greater than 3× the background, it does not have a clearly defined peak shape and is too noisy. This peak should not be included in the Spectral Features Table.

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Submitted SIMS data should be calibrated and should not be binned. Data should be saved as text files (.txt). Data files should contain two columns with the first column being mass (m/z) and the second column being the intensity at the given mass. Column headers are not required.

Submitted data must match the submitted figures and the peaks in the Spectral Features Tables. All spectra are checked and compared with the information and peak identities submitted. Any differences between the submitted data and reported information can result in a revision request or rejection.

Figures can be plotted in the software of your choice as long as they follow the font and formatting guidelines in the SIMS Blank Template Instructions on the SSS website. The X axis of the figure should be labeled “m/z.” The Y axis of the figure should be plotted in “Counts.” Only label major peaks in the spectrum that can be accurately identified. Include one figure per specimen submitted. An example figure is shown in Fig. 3 below. If you need to show two spectral regions to accomplish this, please present them as a stacked plot in one figure as seen in Fig. 4. A maximum of two regions can be shown in the stack plot.

FIG. 3.

Example SIMS spectrum in a single plot. The X-axis should be plotted as m/z. The Y-axis should be plotted in counts. Only label major peaks of known identity. Additional peak identities can be added to the Spectral Features Table for the given spectrum.

FIG. 3.

Example SIMS spectrum in a single plot. The X-axis should be plotted as m/z. The Y-axis should be plotted in counts. Only label major peaks of known identity. Additional peak identities can be added to the Spectral Features Table for the given spectrum.

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FIG. 4.

Example SIMS spectrum using a stacked plot. If you need to highlight more than one spectral region, use a stacked plot as shown in the figure. The X-axes should be plotted as m/z. The Y-axes should be plotted in counts. Only label major peaks of known identity. Additional peak identities can be added to the Spectral Features Table for the given spectrum.

FIG. 4.

Example SIMS spectrum using a stacked plot. If you need to highlight more than one spectral region, use a stacked plot as shown in the figure. The X-axes should be plotted as m/z. The Y-axes should be plotted in counts. Only label major peaks of known identity. Additional peak identities can be added to the Spectral Features Table for the given spectrum.

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As editors at SSS, we want to help you create a successful submission. Please reach out to the editors if you have any questions about your data and how to properly prepare it for publication. We appreciate how much work it takes to put together an SSS submission, and we hope these guidelines will help eliminate any confusion and allow you to minimize corrections and revisions after submitting your SIMS data.

Part of this work was conducted at the Molecular Analysis Facility, a National Nanotechnology Coordinated Infrastructure site at the University of Washington, which is supported in part by the National Science Foundation (NSF) (Grant No. NNCI-1542101), the University of Washington, the Molecular Engineering and Sciences Institute, and the Clean Energy Institute.

The authors have no conflicts to disclose.

Daniel J. Graham: Conceptualization (equal); Writing – original draft (equal); Writing – review & editing (equal).

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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D. J.
Graham
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L. J.
Gamble
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18
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031201
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2023
).