TY - JOUR A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Lohse, V. A1 - Negendank, D. A1 - Kormunda, M. A1 - Esser, N. T1 - Thin SnOx films for surface plasmon resonance enhanced ellipsometric gas sensing (SPREE) N2 - Background: Gas sensors are very important in several fields like gas monitoring, safety and environmental applications. In this approach, a new gas sensing concept is investigated which combines the powerful adsorption probability of metal oxide conductive sensors (MOS) with an optical ellipsometric readout. This concept Shows promising results to solve the problems of cross sensitivity of the MOS concept. Results: Undoped tin oxide (SnOx) and iron doped tin oxide (Fe:SnOx) thin add-on films were prepared by magnetron sputtering on the top of the actual surface plasmon resonance (SPR) sensing gold layer. The films were tested for their sensitivity to several gas species in the surface plasmon resonance enhanced (SPREE) gas measurement. It was found that the undoped tin oxide (SnOx) shows higher sensitivities to propane (C3H8) then to carbon monoxide (CO). By using Fe:SnOx, this relation is inverted. This behavior was explained by a change of the amount of binding sites for CO in the layer due to this iron doping. For hydrogen (H2) no such relation was found but the sensing ability was identical for both layer materials. This observation was related to a different sensing mechanism for H2 which is driven by the Diffusion into the layer instead of adsorption on the surface. Conclusion: The gas sensing selectivity can be enhanced by tuning the properties of the thin film overcoating. A relation of the binding sites in the doped and undoped SnOx films and the gas sensing abilities for CO and C3H8 was found. This could open the path for optimized gas sensing devices with different coated SPREE sensors. KW - Doped tin oxide KW - Ellipsometry KW - Gas sensing KW - Surface plasmon KW - Resonance KW - Thin films KW - Transparent conductive oxides PY - 2017 U6 - https://doi.org/10.3762/bjnano.8.56 SN - 2190-4286 VL - 8 SP - 522 EP - 529 AN - OPUS4-39391 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kormunda, M. A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Sebik, M. A1 - Esser, N. T1 - Preparation of pulsed DC magnetron deposited Fe-doped SnO2 coatings N2 - Iron-doped SnO2 coatings were deposited in a 50 kHz DC-pulsed magnetron sputtering discharge. The pulses had a duration of 4 µs in selected gas mixtures from pure argon up to 60% of oxygen at a constant total pressure of 0.2 Pa. A single target of SnO2 with Fe inset was used. The mass spectrometry study detected the gas-related ions Ar+, O2+ and O+, where the last one becomes the dominant positive ion at higher oxygen contents. Atomic oxygen ions had a higher energy as it resulted from the collision-caused dissociation on the target surface. The tin-related species were detected as Sn+ and SnO+. SnO2+ species were not detected. The deposition rate decreased by using gas mixtures with oxygen as well as the corresponding amount of Sn-related species in the plasma. The increase of oxygen also increased significantly the sheet resistance of the films. The XPS study showed that the iron concentration decreased by using additional oxygen. But the O/Sn ratio in the coatings was constant, contrary to the increased FeO/Fe ratio in the films. An additional analysis of the coatings by spectroscopic ellipsometry has shown a dependence of the polarizability and the permittivity on the amount of oxygen used during the deposition. In contrast, the study has found no such dependence for the absorption of the layers. KW - Coatings KW - Magnetron sputtering KW - Optical properties KW - Sheet resistivity KW - SnO2 PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/pssa.201532882/full U6 - https://doi.org/10.1002/pssa.201532882 SN - 0031-8965 SN - 1862-6300 VL - 213 IS - 9 SP - 2303 EP - 2309 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-38106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Wrobel, J. M. A1 - Brzezinka, Klaus-Werner A1 - Esser, N. A1 - Kautek, Wolfgang T1 - Femtosecond laser irradiation of indium phosphide in air: Raman spectroscopic and atomic force microscopic investigations KW - Femtosecond laser ablation KW - Indium phosphide KW - Raman spectroscopy KW - Atomic force microscopy PY - 2002 SN - 0169-4332 SN - 1873-5584 VL - 202 SP - 272 EP - 282 PB - North-Holland CY - Amsterdam AN - OPUS4-2645 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hertwig, Andreas A1 - Hinrichs, K. A1 - Beck, Uwe A1 - Esser, N. T1 - Editorial to the proceedings of the 7th conference on spectroscopic N2 - The 7th International Conference on Spectroscopic Ellipsometry (ICSE-7) was held in Berlin in June 2016, jointly organised by ICSE and BAM. The publication of the proceedings special issue in Applied Surface Science follows this event. In the special issue, about 100 articles on current topics of optics and surface science related to ellipsometry, polarimetry, and similar techniques are presented, underpinning the high significance of these techniques for many fields of materials science. T2 - 7th International Conference on Spectroscopic Ellipsometry, ICSE-7 CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic ellipsomety PY - 2017 U6 - https://doi.org/10.1016/j.apsusc.2017.04.081 SN - 0169-4332 VL - 2017 IS - 421 SP - 269 EP - 270 PB - Elsevier B.V. AN - OPUS4-42554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kormunda, M. A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Sebik, M. A1 - Pavlik, J. A1 - Esser, N. T1 - Deposition and characterization of single magnetron deposited Fe:SnOx coatings N2 - Coatings deposited by magnetron co-sputtering from a single RF magnetron with a ceramic SnO2 target with iron inset in argon plasma were studied. The mass spectra of the process identified Sn+ and SnO+ species as the dominant species sputtered from the target, but no SnO2+ species were detected. The dominant positive ions in argon plasma are Ar+ species. The only detected negative ions were O-. Sputtered neutral tin related species were not detected. Iron related species were also not detected because their concentration is below the detection limit. The concentration of iron dopant in the tin oxide coatings was controlled by the RF bias applied on the substrate holder while the discharge pressure also has some influence. The iron concentration was in the range from 0.9 at.% up to 19 at.% increasing with the substrate bias while the sheet resistivity decreases. The stoichiometry ratio of O/(Sn + Fe) in the coatings increased from 1.7 up to 2 in dependence on the substrate bias from floating bias (- 5 V) up to - 120 V of RF self-bias, respectively. The tin in the coatings was mainly bonded in Sn4 + state and iron was mainly in Fe2 + state when other tin bonding states were detected only in a small amounts. Iron bonding states in contrary to elemental compositions of the coatings were not influenced by the RF bias applied on the substrate. The coatings showed high transparency in the visible spectral range. However, an increased metallic behavior could be detected by using a higher RF bias for the deposition. The X-ray diffraction patterns and electron microscopy pictures made on the coatings confirmed the presence of an amorphous phase. KW - Metal oxides KW - Transparent conductive oxides (TCO) KW - Magnetron KW - Optical properties KW - Ellipsometry KW - XPS characterzation PY - 2015 U6 - https://doi.org/10.1016/j.tsf.2015.11.009 SN - 0040-6090 VL - 595 IS - Part A SP - 200 EP - 208 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-35281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Negendank, Detlef A1 - Lohse, Volkmar A1 - Kormunda, M. A1 - Esser, N. T1 - Dependence of the optical constants and the performance in the SPREE gas measurement on the thickness of doped tin oxide over coatings N2 - In this study, thickness related changes of the optical properties of doped tin oxide were studied. Two different sets of samples were prepared. The first set was doped with iron or nickel on silicon substrate with thicknesses of 29–56 nm, the second was iron doped on gold/glass substrate with 1.6–6.3 nm. The optical constants were determined by using spectral ellipsometry (SE) followed by modelling of the dielectric function with an oscillator model using Gaussian peaks. The analysis of the optical constants shows a dependence of the refraction and the absorption on the thickness of the doped tin oxide coating. In addition to the tin oxide absorption in the UV, one additional absorption peak was found in the near-IR/red which is related to plasmonic effects due to the doping. This peak shifts from the near-IR to the red part of the visible spectrum and becomes stronger by reducing the thickness, probably due to the formation of metal nanoparticles in this layer. These results were found for two different sets of samples by using the same optical model. Afterwards the second sample set was tested in the Surface Plasmon Resonance Enhanced Ellipsometric (SPREE) gas measurement with CO gas. It was found that the thickness has significant influence on the sensitivity and thus the adsorption of the CO gas. By increasing the thickness from 1.6 nm to 5.1 nm, the sensing ability is enhanced due to a higher coverage of the surface with the over coating. This is explained by the high affinity of CO molecules to the incorporated Fe-nanoparticles in the tin oxide coating. By increasing the thickness further to 6.3 nm, the sensing ability drops because the layer disturbs the SPR sensing effect too much. T2 - 7th International Conference on Spectroscopic Ellipsometry (ICSE-7) DA - 06.06.2016 KW - Surface plasmon resonance KW - Spectroscopic ellipsometry KW - Doped tin oxide KW - Gas sensing KW - Plasmonic absorption PY - 2017 U6 - https://doi.org/10.1016/j.apsusc.2016.11.188 SN - 0169-4332 VL - 421, Teil B SP - 480 EP - 486 PB - Elsevier B.V. AN - OPUS4-42692 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprachmann, J. A1 - Wachsmuth, T. A1 - Bhosale, M. A1 - Burmeister, D. A1 - Smales, Glen Jacob A1 - Schmidt, M. A1 - Kochovski, Z. A1 - Grabicki, N. A1 - Wessling, R. A1 - List-Kratochvil, E. J. W. A1 - Esser, B. A1 - Dumele, O. T1 - Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes N2 - Despite their inherent instability, 4n π systems have recently received significant attention due to their unique optical and electronic properties. In dibenzopentalene (DBP), benzanellation stabilizes the highly antiaromatic pentalene core, without compromising its amphoteric redox behavior or small HOMO−LUMO energy gap. However, incorporating such molecules in organic devices as discrete small molecules or amorphous polymers can limit the performance (e.g., due to solubility in the battery electrolyte solution or low internal surface area). Covalent organic frameworks (COFs), on the contrary, are highly ordered, porous, and crystalline materials that can provide a platform to align molecules with specific properties in a well-defined, ordered environment. We synthesized the first antiaromatic framework materials and obtained a series of three highly crystalline and porous COFs based on DBP. Potential applications of such antiaromatic bulk materials were explored: COF films show a conductivity of 4 × 10−8 S cm−1 upon doping and exhibit photoconductivity upon irradiation with visible light. Application as positive electrode materials in Li-organic batteries demonstrates a significant enhancement of performance when the antiaromaticity of the DBP unit in the COF is exploited in its redox activity with a discharge capacity of 26 mA h g−1 at a potential of 3.9 V vs. Li/Li+ . This work showcases antiaromaticity as a new design principle for functional framework materials. KW - SAXS KW - MOUSE KW - Covalent Organic Frameworks KW - Batteries PY - 2023 U6 - https://doi.org/10.1021/jacs.2c10501 SP - 1 EP - 12 PB - ACS Publications AN - OPUS4-56958 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -