Mario Ziegler

Hierarchically-Designed 3D Flower-Like Composite Nanostructures as an Ultrastable, Reproducible, and Sensitive SERS Substrate

Surface-enhanced Raman spectroscopy (SERS) is an attractive tool in the analytical sciences due to its high specificity and sensitivity. Because SERS-active substrates are only available as two-dimensional arrays, the fabrication of three-dimensional (3D) nanostructures allows for an increased number of hot spots in the focus volume, thus further amplifying the SERS signal. Although a great number of fabrication strategies for powerful SERS substrates exist, the generation of 3D nanostructures with high complexity and periodicity is still challenging. For this purpose, we report an easy fabrication technique for 3D nanostructures following a bottom-up preparation protocol. Enzymatically generated silver nanoparticles (EGNPs) are prepared, and the growth of hierarchically-designed 3D flower-like silica-silver composite nanostructures is induced by applying plasma-enhanced atomic layer deposition (PE-ALD) on the EGNPs. The morphology of these nanocomposites can be varied by changes in the PE-ALD cycle number, and a flower height of up to 10 μm is found. Moreover, the metallized (e.g., silver or gold) 3D nanostructures resulting from 135 PE-ALD cycles of silica creation provide highly reproducible SERS signals across the hydrophobic surface. Within this contribution, the morphological studies, optical properties, as well as the SERS response of these metallized silica-silver composite nanostructures applying vitamin B2 as a model analyte are introduced.

Electrically Excited Plasmonic Nanoruler for Biomolecule Detection

Plasmon-based sensors are excellent tools for a label-free detection of small biomolecules. An interesting group of such sensors are plasmonic nanorulers that rely on the plasmon hybridization upon modification of their morphology to sense nanoscale distances. Sensor geometries based on the interaction of plasmons in a flat metallic layer together with metal nanoparticles inherit unique advantages but need a special optical excitation configuration that is not easy to miniaturize. Herein, we introduce the concept of nanoruler excitation by direct, electrically induced generation of surface plasmons based on the quantum shot noise of tunneling currents. An electron tunneling junction consisting of a metal-dielectric-semiconductor heterostructure is directly incorporated into the nanoruler basic geometry. With the application of voltage on this modified nanoruler, the plasmon modes are directly excited without any additional optical component as a light source. We demonstrate via several experiments that this electrically driven nanoruler possesses similar properties as an optically exited one and confirm its sensing capabilities by the detection of the binding of small biomolecules such as antibodies. This new sensing principle could open the way to a new platform of highly miniaturized, integrated plasmonic sensors compatible with monolithic integrated circuits.

Effects of Plasma Parameter on Morphological and Electrical Properties of Superconducting Nb-N Deposited by MO-PEALD

This paper describes the deposition of superconductive Nb-N thin films in a metal-organic plasma-enhanced atomic layer deposition process using (tert-butylimido)-tris (diethylamino)-niobium and hydrogen plasma as precursors. In extension of our previous work, which investigated the possibility to deposit superconducting Nb-N, we systematically investigated the influence of different plasma parameters on superconducting and morphological properties of the niobium nitride thin film formed during the process. An initial increase of the duration of the plasma dose led to higher transitions temperatures and critical current densities, the optimum being a plasma dose time of 50 s. By decreasing plasma pressure, the resistivity at room temperature decreased, while the transition temperature increased. In addition, Nb-N thin films were deposited onto several substrates such as silicon, thermally grown silica, magnesium oxide (MgO), and r-plane sapphire.

Plasmonic nanoparticles sensors utilizing hybrid modes, electrical excitation, and anisotropic particles

{\rm{T}}_{{\rm{C}}}

Superconducting niobium nitride thin films deposited by metal organic plasma-enhanced atomic layer deposition

values from 6.2 K up to 14 K were achieved independently of the substrate materials. However, films deposited on MgO showed lower

Atomic layer deposition of AlN for thin membranes using trimethylaluminum and H2/N2 plasma

{\rm{T}}_{{\rm{C}}}

Background-Free Bottom-Up Plasmonic Arrays with Increased Sensitivity, Specificity and Shelf Life for SERS Detection Schemes

values. X-ray photoelectron spectroscopy measurement revealed the presence of niobium nitride but also of niobium oxide and oxy-nitride components in the films as well as the existence of a high amount of incorporated carbon impurities. X-ray diffraction measurements revealed two significant reflexes, which could be attributed to niobium nitride only. No crystalline niobium oxide or niobium oxynitride was detected. Thus, the films consisted of a matrix of polycrystalline Nb-N and amorphous or microcrystalline grains of different niobium oxide and oxynitride phases. Due to the fact that the deposited material showed superconductivity especially for ultrathin layers with thicknesses in the nanometer range, these films may be suitable for superconducting nanowire single photon detectors.

Exploiting extreme coupling to realize a metamaterial perfect absorber

Surface Plasmon Resonance (SPR) in metallic nanostructures is an optical effect that can be exploited for the detection of small molecules. There is a broad range of metallic nanostructures supporting different SPR modes, and nanostructures can be even geometrically combined leading to the creation of new hybridised SPR modes. In our study, we investigated the properties of a hybridised SPR mode (gap modes GM) created by the placement of metallic nanoparticles onto metallic layers and its use as a sensitive sensor. A tunneling current passing through a metal-insulator-semiconductor structure can generate supported SPR modes that can be scattered through GM, which was experimentally confirmed. Moreover, we were able to experimentally follow the degradation of anisotropic (silver nanoprism) nanoparticles under ambient conditions in real time. Using atomic force microscopy and optical spectroscopy we observed an anisotropic corrosion that is starting from the tips of the nanoparticles.