ToF-S-SIMS molecular 3D analysis of micro-objects as an alternative to ion beam erosion at large depth: application to single inkjet dots.

Molecular depth profiling is needed to develop high-tech materials optimised to the µm or even up to the nm scale. Recent progress in time-of-flight static secondary ion mass spectrometry (ToF-S-SIMS) offers perspectives to molecular depth profiling. However, at this moment, the methodology is not yet capable to deal with a range of materials science applications because of the limited depth range, the loss of intensity in the subsurface and the loss of depth resolution at large distances from the original surface. Therefore, the purpose of this paper is to develop a complementary approach for the molecular 3D analysis at large depth, using a combination of ultra-low angle microtomy (ULAM) and surface analysis of the sectioned material with ToF-S-SIMS. Single inkjet dots with a diameter of 100 µm and height of 22 µm on a PET substrate have been used as a test system for the methodology. It is demonstrated that the use of a diamond knife allows the molecular composition and distribution of components within the microscopic feature to be probed with a lateral resolution of 300 nm. Hence the methodology approaches the physical limit for ion imaging of organic components with local concentrations in the % range. In practice, the achievable depth resolution with ULAM-S-SIMS is ultimately limited by the surface roughness of the section. Careful optimisation of the ULAM step has resulted in a surface roughness within 6 nm (R(a) value) at a depth of 21 µm. This offers perspective to achieve 3D analysis with a depth resolution as good as 18 nm at such a large distance from the surface. Furthermore, the ULAM-S-SIMS approach is applicable to materials unamenable to ion beam erosion. However, the method is limited to dealing with, for instance, Si or glass substrates that cannot be sectioned with a microtomy knife. Furthermore, sufficient adhesion between stacked layers or between the coating and substrate is required. However, it is found that the approach is applicable to a wide variety of industrially important (multi)layers of polymers on a polymer substrate.

Ultra-low-angle microtomy and static secondary ion mass spectrometry for molecular depth profiling of UV-curable acrylate multilayers at the nanoscale.

Development of sustainable materials requires methods capable of probing the molecular composition of samples not only at the surface but also in depth. Static secondary ion mass spectrometry (S-SIMS) characterises the distribution of organic and inorganic compounds at the surface. Ultra-low-angle microtomy (ULAM) has been studied as an alternative or complementing method to the molecular depth profiling with, e.g. C(60)(+) projectiles. Acrylate-based multilayers relevant to industrial inkjet printing have been sectioned at a cutting angle below 1 degrees. In this way, analysis of the section over a distance of 1 microm allows a depth range in the order of a few nm in the original sample to be achieved. Adequate procedures to optimise the ULAM step and minimise or control the cutting artefacts have been developed. The combination of ULAM with S-SIMS has allowed a depth resolution of 10 nm to be obtained for components at a distance of 35 microm from the surface.

Feasibility of static secondary ion mass spectrometry to study physicochemical interactions between organic components and silver in thermographic systems.

Chemical engineering of high-technology products requires elucidation of intermolecular interactions in complex materials. As part of an extensive study on thermographic systems, static secondary ion mass spectrometry (S-SIMS) was used to probe the physicochemical behaviour of active compounds, such as different tone modifiers and stabilisers, on silver. In particular, the feasibility of detecting adsorption and/or binding of individual additives and mixtures to silver was examined. Substrates prepared by sputter coating silver on silicon wafers were exposed to solutions of the studied compounds in 2-butanone. The signal intensities measured with S-SIMS for the ad-layers showed reproducibility to within 10%. Radical ions containing silver such as [M-H+Ag]+ * were used as evidence for the formation of bonds in the solid. Also the [M-H+2Ag]+ ions could be assigned to chemisorbed species while [M+Ag]+ ions could be formed by adduct ionisation of molecules with co-ejected Ag+ ions. The signal intensities of [M-H+Ag]+ * and [M-H+2Ag]+ ions were used to monitor the adsorption quantitatively as a function of time.

Comparison of mono- and polyatomic primary ions for the characterization of organic dye overlayers with static secondary ion mass spectrometry.

Organic carbocyanine dye coatings have been analyzed by time-of-flight static secondary ion mass spectrometry (TOF-S-SIMS) using three types of primary ions: Ga(+) operating at 25 keV, and Xe(+) and SF(5) (+) both operating at 9 keV. Secondary ion yields obtained with these three primary ions have been compared for coatings with different layer thickness, varying from (sub)-monolayer to multilayers, on different substrates (Si, Ag and AgBr cubic microcrystals). For (sub)-monolayers deposited on Ag, Xe(+) and SF(5) (+) primary ions generate similar precursor ion intensities, but with Ga(+) slightly lower precursor ion intensities were obtained. Thick coatings on Ag as well as mono- and multilayers on Si produce the highest precursor and fragment ion intensities with the polyatomic primary ion. The yield difference between SF(5) (+) and Xe(+) can reach a factor of 6. In comparison with Ga(+), yield enhancements by up to a factor of 180 are observed with SF(5) (+). For the mass spectrometric analysis of dye layers on AgBr microcrystals, SF(5) (+) again proves to be the primary ion of choice.