Laboratory for ToF-SIMS Analysis
Atomic and molecular information with high sensitivity

With secondary ion mass spectrometry (ToF-SIMS analysis) the atomic or elemental and molecular composition in the top 1-3 monolayers of a solid can be analyzed (static SIMS analysis). For this purpose, the surface to be examined is bombarded with charged particles (ions) of up to 30 keV energy and the secondary ions ejected from the surface are analyzed with regard to their mass (surface mass spectrometry). Elements and molecules can be detected simultaneously in ToF-SIMS  analysis. The use of time-of-flight analyzers for mass detection leads to a high detection sensitivity (ppm to ppb). A quantification of the data requires the use of suitable standard samples in the laboratory. Semi-quantitative data can be obtained in the analysis if the samples to be compared have a similar basic chemical composition. Ask the experts in the laboratory for ToF-SIMS analysis.

ToF-SIMS analysis can resolve the chemical composition in 2D (imaging surface analysis) and achieves a lateral resolution of 300 nm in routine operation. A higher lateral resolution is possible in many cases. The experienced laboratory for ToF-SIMS measurement will be glad to help you.

A sample can also be removed step by step by continuous ion bombardment (ion sputtering, depth profiling, sputtering, dynamic SIMS). In this way, elemental information is obtained as a function of depth. Modern ToF-SIMS analysis instruments allow the obtainment of depth profiles of both inorganic (elements) and organic (molecular) layer structures. By combining imaging (figure) and depth profiling in ToF-SIMS analysis, the three-dimensional structure of a solid or the areas close to the surface can also be analyzed by 3D imaging (3D micro-area analysis).

The effort for sample preparation for ToF-SIMS analysis in the laboratory are comparatively low. In most cases, the samples can be analyzed without further pre-treatment. However, the material has to be vacuum compatible. In addition to solids, powders and drying residues of liquids can also be analyzed.

For shipping samples, we recommend to wrap samples in customary aluminum foil or clean paper (e.g. filter paper) to avoid unwanted contamination during sample handling or during transport. However, even if unwanted organic contamination occurs due to handling or preparation, ToF-SIMS surface analysis is possible after appropriate cleaning in our laboratory, as shown in the following example.

In the past, chemical (rinsing) or mechanical (scratching, cutting) cleaning approaches were mostly used to remove contaminations in the field of surface analysis. However, these preparation methods carry the risk of new contaminations, they are time-consuming and in the case of structured systems (e.g. semiconductor structures), their use is limited. In contrast, in-situ cleaning by bombardment with Ar cluster ions allows a particularly efficient, gentle and fast removal of molecular surface contaminations. The Ar-Cluster sources required for this are an optional component of the latest ToF-SIMS device generation and can of course be found on several ToF-SIMS analysis devices in the Tascon laboratories. By selecting suitable bombardment conditions, molecular contamination layers with thicknesses from a few nm up to many µm can be selectively removed without damaging deeper molecular structures.

The mode of operation of the in-situ Ar-Cluster cleaning in a ToF-SIMS device is illustrated by the following example of a component based on a polypropylene (PP). The surface of the black moulded component was covered with an optically easily visible dark coating after prolonged storage. In investigations using confocal microscopy and white-light interferometry, this coating turned out to be a crystalline material with average heights of around 10 µm (see round figures).

To identify the chemical composition of this unwanted coating, ToF-SIMS analyses should be carried out additionally. A direct analysis of the surface in an area with optically well visible residues (red marking in the micro-image and angular secondary ion images in the upper line) provided evidence of a homogeneous polydimethylsiloxane (PDMS) layer but no evidence of crystalline structures. Only after an in-situ Ar-cluster cleaning of the sample surface lasting only a few seconds, deeper layers could be exposed and the imaging of glycerol monostearate (GMS) containing regions became possible (images bottom line).

A comparison of the depicted GMS structures with the microscopic images clearly shows that the lateral distribution of the GMS corresponded with the optically detectable discolorations.

Tascon - Your new partner for ToF-SIMS analysis service

Do you have more questions on ToF-SIMS analysis? Or are you interested in details about in-situ sample purification in the Tascon laboratory? We would be pleased if you contact us. Furthermore, you have the possibility to download more details on ToF-SIMS analysis in the Technical Note ToF-SIMS under the following link.