18 research outputs found
Plasmonisch aktive Schichten und Nanostrukturen fĂŒr die Material- und Sensorentwicklung
Der Schwerpunkt der Arbeit liegt in der Evaluierung neuer Materialkombinationen und kostengĂŒnstiger Herstellungstechnologien fĂŒr die Realisierung definierter, spezieller optischer Eigenschaften von OberflĂ€chen, Nanopartikeln (NP) und -strukturen auf Basis von Schichttechnologien, insbesondere in Hinblick auf die Integration in Sensorplattformen fĂŒr die Bioanalytik. Plasmonisch aktive OberflĂ€chen z.B. als LSPR-OberflĂ€chen oder SERS-Substrate erfordern anwendungsbezogene Eigenschaften. Deshalb werden in der Arbeit unterschiedliche Herstellungsverfahren von NP und Strukturen, wie die Temperatur- und Matrix-induzierten Verfahren, ein Laser-induziertes Verfahren und das Template-Stripping untersucht und die experimentellen Ergebnisse diskutiert. Als Schichtmaterialien wird auf fcc-Edelmetalle wie Au und Ag eingegangen, die fĂŒr die Bioanalytik besonders interessant sind. Bei der Sputter-Abscheidung wachsen diese substratunabhĂ€ngig mit einer (111)-Vorzugsorientierung auf und bilden, insbesondere bei niedrigen DrĂŒcken, sehr glatte und dicht gepackte OberflĂ€chen aus. Diese glatten OberflĂ€chen verbessern die GĂŒte der Schicht und verlĂ€ngern damit die PropagationslĂ€nge der SPP. Die Plasmonik von NP, d.h. die Dichteoszillationen der freien LadungstrĂ€ger, werden nicht nur von der GröĂe, der Form und dem Material, sondern auch von dem Umgebungsmedium bestimmt. Das Aufbringen einer Schicht in fester Phase auf die NP - in dieser Arbeit SiO2, SiNx, ZnO, Al2O3, STO oder YBCO - beeinflusst nicht nur die LSPR-Bande durch einen anderen Brechungsindex der Umgebung, sondern wirkt sich auch auf den Partikelbildungsprozess bzw. Umformungsprozess selbst aus. Als besonders interessant stellten sich die Matrix-induzierte NP-Bildung unter Verwendung einer STO-Schicht und der UV-Laser-induzierte Prozess heraus. Weiterhin werden messtechnische AnsĂ€tze fĂŒr hybride Bioanalytik-Plattformen realisiert, mit denen durch die Kombination von optisch sensitiven Nachweismethoden (Cavity-Ring-Down Verfahren und planare Ring-Wellenleiter-Strukturen) mit der Plasmonik eine Steigerung bezĂŒglich SelektivitĂ€t und SensitivitĂ€t in der Bioanalytik erreicht werden kann. So war es z.B. möglich mit der Sensorplattform basierend auf der Cavity-Ring-Down Methode kombiniert mit der NP-Plasmonik und mikrofluidischem System einen DNA-Nachweis mit einem LOD von ca. 3fM zu realisieren.The focus of the work is the investigation of new material combinations and cost-effective fabrication technologies realizing defined, special optical properties of surfaces, nanoparticles (NP) and structures based on thin film technologies, especially with regard to the integration in sensor platforms for bioanalytics. Plasmonically active surfaces for instance as LSPR surfaces or SERS substrates require application-related properties. For this reason, different fabrication methods of NP and structures such as temperature- and matrix-induced methods, a laser-induced method and the template stripping process are investigated and the experimental results are discussed. The NP materials are fcc-precious metals such as Au and Ag, which are of particular interest for bioanalytics. By sputter deposition, they grow independently of the substrate with a (111) preference orientation and form very smooth and densely packed surfaces, especially at low Ar pressures. These smooth surfaces improve the quality of the layers or surfaces and thus extending the propagation length of the SPP. The NP plasmonics, i.e. the density oscillation of the free charge carriers, are determined not only by the size, the shape and the material of the NP but also by the surrounding medium. The deposition of a layer of solid phase onto the NP - in this work SiO2, SiNx, ZnO, Al2O3, STO or YBCO - not only affects the LSPR band by the different refractive index of the environment, but also affects the particle formation process or transformation process itself. The matrix-induced NP formation using a STO cover layer and the UV laser-induced process were of particular interest. Furthermore, measurement setups for hybrid bioanalytical platforms will be realized, which can increase the selectivity and sensitivity in bioanalytics by combination of optically sensitive detection methods (cavity-ring down and planar ring waveguide structures) with plasmonics. Thus, it was for instance possible to realize DNA detection with a LOD of about 3fM based on the cavity-ring down method combined with NP plasmonics and microfluidic systems
Recommended from our members
Fabrication of self-assembled spherical Gold Particles by pulsed UV Laser Treatment
We report on the fabrication of spherical Au spheres by pulsed laser treatment using a KrF excimer laser (248ânm, 25âns) under ambient conditions as a fast and high throughput fabrication technique. The presented experiments were realized using initial Au layers of 100ânm thickness deposited on optically transparent and low cost Borofloat glass or single-crystalline SrTiO3 substrates, respectively. High (111)-orientation and smoothness (RMS â 1ânm) are the properties of the deposited Au layers before laser treatment. After laser treatment, spheres with size distribution ranging from hundreds of nanometers up to several micrometers were produced. Single-particle scattering spectra with distinct plasmonic resonance peaks are presented to reveal the critical role of optimal irradiation parameters in the process of laser induced particle self-assembly. The variation of irradiation parameters like fluence and number of laser pulses influences the melting, dewetting and solidification process of the Au layers and thus the formation of extremely well shaped spherical particles. The gold layers on Borofloat glass and SrTiO3 are found to show a slightly different behavior under laser treatment. We also discuss the effect of substrates.We report on the fabrication of spherical Au spheres by pulsed laser treatment using a KrF excimer laser (248ânm, 25âns) under ambient conditions as a fast and high throughput fabrication technique. The presented experiments were realized using initial Au layers of 100ânm thickness deposited on optically transparent and low cost Borofloat glass or single-crystalline SrTiO3 substrates, respectively. High (111)-orientation and smoothness (RMS â 1ânm) are the properties of the deposited Au layers before laser treatment. After laser treatment, spheres with size distribution ranging from hundreds of nanometers up to several micrometers were produced. Single-particle scattering spectra with distinct plasmonic resonance peaks are presented to reveal the critical role of optimal irradiation parameters in the process of laser induced particle self-assembly. The variation of irradiation parameters like fluence and number of laser pulses influences the melting, dewetting and solidification process of the Au layers and thus the formation of extremely well shaped spherical particles. The gold layers on Borofloat glass and SrTiO3 are found to show a slightly different behavior under laser treatment. We also discuss the effect of substrates
Biomimic Vein-Like Transparent Conducting Electrodes with Low Sheet Resistance and Metal Consumption
Abstract: In this contribution, inspired by the excellent resource management and material transport function of leaf veins, the electrical transport function of metallized leaf veins is mimicked from the material transport function of the vein networks. By electroless copper plating on real leaf vein networks with copper thickness of only several hundred nanometre up to several micrometre, certain leaf veins can be converted to transparent conductive electrodes with an ultralow sheet resistance 100 times lower than that of state-of-the-art indium tin oxide thin films, combined with a broadband optical transmission of above 80% in the UVâVISâIR range. Additionally, the resource efficiency of the vein-like electrode is characterized by the small amount of material needed to build up the networks and the low copper consumption during metallization. In particular, the high current density transport capability of the electrode of > 6000 A cmâ2 was demonstrated. These superior properties of the vein-like structures inspire the design of high-performance transparent conductive electrodes without using critical materials and may significantly reduce the Ag consumption down to < 10% of the current level for mass production of solar cells and will contribute greatly to the electrode for high power density concentrator solar cells, high power density Li-ion batteries, and supercapacitors.[Figure not available: see fulltext.]. © 2020, © 2020, The Author(s)
Recommended from our members
Copper Iodide on Spacer Fabrics as Textile Thermoelectric Device for Energy Generation
The integration of electronic functionalities into textiles for use as wearable sensors, energy harvesters, or coolers has become increasingly important in recent years. A special focus is on efficient thermoelectric materials. Copper iodide as a p-type thermoelectrically active, nontoxic material is attractive for energy harvesting and energy generation because of its transparency and possible high-power factor. The deposition of CuI on polyester spacer fabrics by wet chemical processes represents a great potential for use in textile industry for example as flexible thermoelectric energy generators in the leisure or industrial sector as well as in medical technologies. The deposited material on polyester yarn is investigated by electron microscopy, x-ray diffraction and by thermoelectric measurements. The Seebeck coefficient was observed between 112 and 153 ”V/K in a temperature range between 30 °C and 90 °C. It is demonstrated that the maximum output power reached 99 nW at temperature difference of 65.5 K with respect to room temperature for a single textile element. However, several elements can be connected in series and the output power can be linear upscaled. Thus, CuI coated on 3D spacer fabrics can be attractive to fabricate thermoelectric devices especially in the lower temperature range for textile medical or leisure applications
Non-destructive depth reconstruction of Al-AlCu layer structure with nanometer resolution using extreme ultraviolet coherence tomography
Non-destructive cross-sectional characterization of materials systems with a
resolution in the nanometer range and the ability to allow for time-resolved
in-situ studies is of great importance in material science. Here, we present
such a measurements method, extreme ultraviolet coherence tomography (XCT). The
method is non-destructive during sample preparation as well as during the
measurement, which is distinguished by a negligible thermal load as compared to
electron microscopy methods. Laser-generated radiation in the extreme
ultraviolet (XUV) and soft x-ray range is used for characterization. The
measurement principle is interferometric and the signal evaluation is performed
via an iterative Fourier analysis. The method is demonstrated on the metallic
material system Al-AlCu and compared to electron and atomic force
microscopy measurements. We also present advanced reconstruction methods for
XCT which even allow for the determination of the roughness of outer and inner
interfaces.Comment: First two authors contributed equally to this work and are ordered
alphabetically. 14 page
Recommended from our members
Absolute EUV reflectivity measurements using a broadband high-harmonic source and an in situ single exposure reference scheme
We present a tabletop setup for extreme ultraviolet (EUV) reflection spectroscopy in the spectral range from 40 to 100âeV by using high-harmonic radiation. The simultaneous measurements of reference and sample spectra with high energy resolution provide precise and robust absolute reflectivity measurements, even when operating with spectrally fluctuating EUV sources. The stability and sensitivity of EUV reflectivity measurements are crucial factors for many applications in attosecond science, EUV spectroscopy, and nano-scale tomography. We show that the accuracy and stability of our in situ referencing scheme are almost one order of magnitude better in comparison to subsequent reference measurements. We demonstrate the performance of the setup by reflective near-edge x-ray absorption fine structure measurements of the aluminum L2/3 absorption edge in α-Al2O3 and compare the results to synchrotron measurements
Porous spherical gold nanoparticles via a laser induced process
Nanoparticles consisting of a mixture of several metals and also porous nanoparticles due to their special structure exhibit properties that find applications in spectroscopic detection or catalysis. Different approaches of top down or bottom up technologies exist for the fabrication of such particles. We present a novel combined approach for the fabrication of spherical porous gold nanoparticles on low-cost glass substrates under ambient conditions using a UV-laser induced particle preparation process with subsequent wet chemical selective etching. In this preparation route, nanometer-sized branched structures are formed in spherical particles. The laser process, which is applied to a silver/gold bilayer system with different individual layer thicknesses, generates spherical mixed particles in a nanosecond range and influences the properties of the fabricated nanoparticles, such as the size and the mixture and thus the spectral response. The subsequent etching process is performed by selective wet chemical removal of silver from the nanoparticles with diluted nitric acid. The gold to silver ratio was investigated by energy-dispersive X-ray spectroscopy. The porosity depends on laser parameters and film thickness as well as on etching parameters such as time. After etching, the surface area of the remaining Au nanoparticles increases which makes these particles interesting for catalysis and also as carrier particles for substances. Such substances can be positioned at defined locations or be released in appropriate environments. Absorbance spectra are also analyzed to show how the altered fractured shape of the particles changes localized plasmon resonances of the resultingt particles
Recommended from our members
Combining super-resolution microcopy with neuronal network recording using magnesium fluoride thin films as cover layer for multi-electrode array technology
We present an approach for fabrication of reproducible, chemically and mechanically robust functionalized layers based on MgF2 thin films on thin glass substrates. These show great advantages for use in super-resolution microscopy as well as for multi-electrode-array fabrication and are especially suited for combination of these techniques. The transparency of the coated substrates with the low refractive index material is adjustable by the layer thickness and can be increased above 92%. Due to the hydrophobic and lipophilic properties of the thin crystalline MgF2 layers, the temporal stable adhesion needed for fixation of thin tissue, e.g. cryogenic brain slices is given. This has been tested using localization-based super-resolution microscopy with currently highest spatial resolution in light microscopy. We demonstrated that direct stochastic optical reconstruction microscopy revealed in reliable imaging of structures of central synapses by use of double immunostaining of post- (homer1 and GluA2) and presynaptic (bassoon) marker structure in a 10â”m brain slice without additional fixing of the slices. Due to the proven additional electrical insulating effect of MgF2 layers, surfaces of multi-electrode-arrays were coated with this material and tested by voltage-current-measurements. MgF2 coated multi-electrode-arrays can be used as a functionalized microscope cover slip for combination with live-cell super-resolution microscopy