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Bad Münster am Stein-Ebernburg, Germany

Rafati A.,University of Washington | Ter Veen R.,Tascon GmbH | Castner D.G.,University of Washington
Surface and Interface Analysis | Year: 2013

With the widespread use of engineered nanoparticles for biomedical applications, detailed surface characterization is essential for ensuring reproducibility and the quality/suitability of the surface chemistry to the task at hand. One important surface property to be quantified is the overlayer thickness of self-assembled monolayer (SAM) functionalized nanoparticles, as this information provides insight into SAM ordering and assembly. We demonstrate the application of high sensitivity low-energy ion scattering (HS-LEIS) as a new analytical method for the fast thickness characterization of SAM functionalized gold nanoparticles (AuNPs). HS-LEIS demonstrates that a complete SAM is formed on 16-mercaptohexadecanoic acid (C16COOH) functionalized 14 nm AuNPs. HS-LEIS also experimentally provides SAM thickness values that are in good agreement with previously reported results from simulated electron spectra for surface analysis of X-ray photoelectron spectroscopy data. These results indicate HS-LEIS is a valuable surface analytical method for the characterization of SAM functionalized nanomaterials. © 2013 John Wiley & Sons, Ltd. Source

Liu J.,Imperial College London | Chater R.J.,Imperial College London | Hagenhoff B.,Tascon GmbH | Morris R.J.H.,University of Warwick | Skinner S.J.,Imperial College London
Solid State Ionics | Year: 2010

Isotopic surface oxygen exchange and its subsequent diffusion have been measured using secondary ion mass spectrometry in the fast ionic conductor La2Mo2O9. A silver coating was applied to the sample surface to enhance the surface exchange process for dry oxygen. Contrary to previous studies performed using a wet atmosphere, no grain boundary diffusion tail was observed under these optimized dry exchange conditions. The activation energy for oxygen diffusion was found to be 0.66(± 0.09) eV at high temperature (> 570 °C), and 1.25(± 0.01) eV at low temperature (< 570 °C). Time-of-Flight secondary ion mass spectrometry was employed to investigate the correlation between the silver coating and the 18O concentration on the sample surface. A close correlation between the presence of silver and oxygen incorporation on the surface was observed. © 2010 Elsevier B.V. All rights reserved. Source

Niehuis E.,ION TOF GmbH | Mollers R.,ION TOF GmbH | Rading D.,ION TOF GmbH | Cramer H.-G.,ION TOF GmbH | Kersting R.,Tascon GmbH
Surface and Interface Analysis | Year: 2013

Ar cluster sputtering of organic multilayers such as organic light-emitting diode model structures and Irganox delta layers is studied with time-of-flight secondary ion mass spectroscopy in the dual beam mode. Results for sputtering yield volumes and depth resolution are presented for Ar clusters with sizes from 500 to 5000 atoms in the energy range from 2.5 to 20 keV. The sputtering yield volume shows a linear dependence on the energy per atom for all materials in this study with a material-dependent threshold below 1 eV/atom. The sputtering yield volume at a given energy per atom increases with the cluster size. At constant beam energies, the sputtering yield volume decreases slightly with increasing cluster size. The depth resolution is investigated for the two model systems as a function of energy and cluster size, and it will be shown that the depth resolution depends mainly on the sample roughening. The depth resolution is approximately proportional to the depth of the impact crater at a given cluster size and energy. The optimum depth resolution achieved is in the range of 4-5 nm and is fairly constant with depth. At very low energies per atom close to the threshold energy, ripple formation is observed that leads to a fast degradation of the depth resolution with depth. This can be completely eliminated by fast sample rotation. Finally, the perspective of 3D analysis of organic devices with high depth resolution in the dual beam mode will be discussed. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Source

Clark P.A.,Tascon United States | Hagenhoff B.,Tascon GmbH | Kersting R.,Tascon GmbH | Tallarek E.,Tascon GmbH
Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics | Year: 2016

The development of cluster primary ion sources such as Aun +, Bin +, SF5 +, C60 +, and Arn + has been an exciting advancement in SIMS analysis. Relative to atomic primary ion sources, cluster ion sources provide higher secondary ion yields. Furthermore, C60 + and Arn + impart significantly less chemical damage to the sample thus enabling molecular depth profiling. Molecular depth profiling using cluster primary ion sources is routinely used to characterize a wide range of commercially important materials, including organic light emitting diode, biomaterials and pharmaceuticals, adhesives, and architectural paints and coatings. This paper highlights the application of time of flight secondary ion mass spectrometry (ToF-SIMS) to study contact lenses and acrylic-based paints. In the first application, ToF-SIMS was used to investigate the surface composition of two commercial contact lenses. Lens material I is composed of 2-hydroxy-ethyl methacrylate (HEMA) and glycerol methacrylate while lens material II is composed of HEMA and 2-methacryloxyethyl phosphorylcholine cross-linked with ethyleneglycol dimethacrylate. The ToF-SIMS data confirm the presence of the 2-methacryloxyethyl phosphorylcholine on the surface of lens material II. ToF-SIMS was also used to characterize a HEMA-based contact lens which had been worn for about 4 weeks. The analysis reveals the presence of N-containing species, fatty acids, phosphorylcholine, and dioctyldecyl dimethyl ammonium. Arn + gas cluster ion beams (GCIB) depth profiling indicates the N-containing species, the fatty acids, and the dioctyldecyl dimethyl ammonium are concentrated at the surface. In the second application, a combination of O2 + and Arn + GCIB depth profiling was used to study the pigment levels in acrylic-based paints. The O2 + beam was used to profile into the bulk of the dried paint film and Arn + gas cluster beam was then used to remove the damaged material. ToF-SIMS analysis of the crater bottom reveals differences in pigment levels. The combined O2 + and Arn + GCIB depth profiling is an effective way of characterizing materials composed of both organic and inorganic components. © 2016 American Vacuum Society. Source

Heller D.,Tascon GmbH | Hagenhoff B.,Tascon GmbH | Engelhard C.,University of Siegen
Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics | Year: 2016

This paper presents a case study for the application of multivariate data analysis (MVA) to time-of-flight secondary ion mass spectrometry (ToF-SIMS) data from sample sets of mainly unknown surface composition. Aged lithium-ion battery (LIB) anodes were used as the test sample set due to their relatively complex composition. For example, LIB samples typically contain a large variety of different and often unidentified degradation products that complicate manual data processing. In this work, principal component analysis (PCA) was applied as a first step to find and classify relevant but unknown peaks in the ToF-SIMS mass spectra. As a result, peak identification was simplified in such a way that the chemical nature of 76% of the characteristic but previously unknown peaks was successfully identified. In a second step, multivariate curve resolution (MCR) was applied to depth profiles of the battery anodes for the first time, and a layered structure of the model samples was successfully determined. This approach also provided an efficient way to compare the layers' structure and the thickness across different samples. In addition to MCR, PCA was used on ToF-SIMS data to investigate all of the layer compositions of the complete sample set simultaneously. It is demonstrated that ToF-SIMS data from rarely characterized data sets can be processed successfully using MVA methods even if a priori knowledge of the sample sets is very limited. With respect to the test samples, the combination ToF-SIMS and MVA proved to be an attractive method to study the influence of different additives (vinylene carbonate, fluoroethylene carbonate, and ethylene sulfite) that appeared in the mass spectra, and was therefore helpful in understanding the formation of different degradation products in LiPF6-containing battery anodes. © 2016 American Vacuum Society. Source

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