TY - JOUR A1 - Florian, Camilo A1 - Fischer, Daniel A1 - Freiberg, K. A1 - Duwe, M. A1 - Sahre, Mario A1 - Schneider, S. A1 - Hertwig, Andreas A1 - Krüger, Jörg A1 - Rettenmayr, M. A1 - Beck, Uwe A1 - Undisz, A. A1 - Bonse, Jörn T1 - Single Femtosecond Laser-Pulse-Induced Superficial Amorphization and Re-Crystallization of Silicon JF - Materials N2 - Superficial amorphization and re-crystallization of silicon in <111> and <100> orientation after irradiation by femtosecond laser pulses (790 nm, 30 fs) are studied using optical imaging and transmission electron microscopy. Spectroscopic imaging ellipsometry (SIE) allows fast data acquisition at multiple wavelengths and provides experimental data for calculating nanometric amorphous layer thickness profiles with micrometric lateral resolution based on a thin-film layer model. For a radially Gaussian laser beam and at moderate peak fluences above the melting and below the ablation thresholds, laterally parabolic amorphous layer profiles with maximum thicknesses of several tens of nanometers were quantitatively attained. The accuracy of the calculations is verified experimentally by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (STEM-EDX). Along with topographic information obtained by atomic force microscopy (AFM), a comprehensive picture of the superficial re-solidification of silicon after local melting by femtosecond laser pulses is drawn. KW - Femtosecond laser KW - Silicon KW - Amorphization KW - Crystallization KW - Spectroscopic imaging ellipsometry PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523687 UR - https://www.mdpi.com/1996-1944/14/7/1651 DO - https://doi.org/10.3390/ma14071651 SN - 1996-1944 VL - 14 IS - 7 SP - 1651-1 EP - 1651-21 PB - MDPI AG CY - Basel, Switzerland AN - OPUS4-52368 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jensen, S. A. A1 - Rosu, Dana Maria A1 - Hertwig, Andreas A1 - Hansen, P.-E. T1 - Use of Rayleigh-Rice Theory for Analysis of Ellipsometry Data on Rough CIGS Films JF - Phys. Status Solidi C N2 - Ellipsometry is a useful tool for studying the optical properties of thin films such as photovoltaic devices. We employ Müller matrix ellipsometry to study the thin film photovoltaic material copper indium gallium selenide Cu(In,Ga) Se2 (CIGS), a commercially relevant material with high energy conversion efficiency. Confocal microscopy reveals an rms roughness of 68 nm, which greatly affects the ellipsometry data. Rayleigh-Rice theory is employed to account for the optical properties of the surface roughness in the ellipsometry experiment, and a library search method is used to compare Müller parameters calculated for various CIGS compositions, to the measured data. The Müller parameters calculated with the Rayleigh-Rice model are found to correspond well with the measured data, and a surface roughness of 37nm and a correlation length of 125nm are extracted. KW - Photovoltaics KW - Thin Films KW - Ellipsometry KW - Scattering Theory KW - Optical Wavefield KW - Simulation KW - Müller Polarimetry KW - Multidimensional Spectroscopy PY - 2017 DO - https://doi.org/10.1002/pssc.201700217 SN - 1862-6351 VL - 14 IS - 12 SP - 1700217, 1 EP - 5 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-43390 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, Lena A1 - Tavernaro, Isabella A1 - Eckert, J. G. A1 - Lutowski, M. A1 - Geißler, D. A1 - Hertwig, A. A1 - Hidde, G. A1 - Bigall, N. C. A1 - Resch-Genger, Ute T1 - Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads JF - scientific reports N2 - Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 μm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials. KW - Optical spectroscopy KW - Particle KW - Optical assay KW - IR spectroscopy; conductometry KW - Fluorescence KW - Quantum yield KW - Quality assurance KW - Nano KW - Synthesis KW - Surface chemistry KW - Quantification KW - Method PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581502 DO - https://doi.org/10.1038/s41598-023-38518-7 SN - 2045-2322 VL - 13 IS - 1 SP - 1 EP - 15 PB - Springer Nature AN - OPUS4-58150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hertwig, Andreas A1 - De Castro, F.A. T1 - Newsletter - Metrology for the manufacturing of thin films KW - Metrology KW - Thin films KW - Optoelectronics KW - Photovoltaics KW - Coatings technology KW - Traceability PY - 2012 UR - http://projects.npl.co.uk/optoelectronic_films/documents/EMRP%20ThinFilms_Newsletter%20Feb%202012.pdf IS - February SP - 1 EP - 4 AN - OPUS4-25505 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schalk, O. A1 - Yang, J.-P. A1 - Hertwig, Andreas A1 - Hippler, H. A1 - Unterreiner, A.N. T1 - Vibrational cooling in the liquid phase studied by ultrafast investigations of cycloheptatriene JF - Molecular physics N2 - Solvent-mediated vibrational relaxation in UV pump-probe experiments has been studied using cycloheptatriene (CHT) and its perdeuterated counterpart (CHTd8) as model systems. Transient spectra containing absolute e(t) values are obtained by a modified Sulzer-Wieland ansatz and a global fit function for vibrational relaxation is proposed. KW - Vibrational cooling KW - Ultrafast dynamics KW - Cycloheptatriene KW - Internal conversion KW - Sulzer-Wieland model PY - 2009 DO - https://doi.org/10.1080/00268970903193010 SN - 0026-8976 SN - 1362-3028 VL - 107 IS - 20 SP - 2159 EP - 2167 PB - Taylor & Francis CY - London AN - OPUS4-20654 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -