arXiv subjects

Niels Benson

Publications and source records attributed to Niels Benson.

6 recordsLinked to original sources

arXiv2026

All-Dielectric Ceramic 3-D Printed Unidirectional Leaky-Wave Antenna at mm-Wave Frequencies

An all-dielectric leaky-wave antenna, radiating unidirectionally at broadside without the use of a metallic ground plane, is designed and manufactured. It operates in the 70-90 GHz frequency range with a design broadside frequency of 77 GHz. The design process makes use of the theory of photonic bandgaps to position a -1 harmonic at the broadside frequency on the second Bragg-condition point. The structure is then modified to close the bandgap and to simultaneously guarantee maximum total field coupling to the relevant radiating harmonic, ensuring radiation unidirectionality. The antenna is manufactured with an Al2O3 ceramic printing process, demonstrating its manufacturing potential for complex low-loss high-frequency structures. Simulations agree well with measurements, with the main deviation being a 1 GHz frequency shift that could be reproduced in simulation. The antenna prototype shows a scanning range of -18°-22° and gain values above 23 dBi. More than 85 % of the radiation power is radiated unidirectionally at broadside, with simulations showing potential to attain 98 %.

physics.optics↗

arXiv2025

Defect Segmentation in OCT scans of ceramic parts for non-destructive inspection using deep learning

Non-destructive testing (NDT) is essential in ceramic manufacturing to ensure the quality of components without compromising their integrity. In this context, Optical Coherence Tomography (OCT) enables high-resolution internal imaging, revealing defects such as pores, delaminations, or inclusions. This paper presents an automatic defect detection system based on Deep Learning (DL), trained on OCT images with manually segmented annotations. A neural network based on the U-Net architecture is developed, evaluating multiple experimental configurations to enhance its performance. Post-processing techniques enable both quantitative and qualitative evaluation of the predictions. The system shows an accurate behavior of 0.979 Dice Score, outperforming comparable studies. The inference time of 18.98 seconds per volume supports its viability for detecting inclusions, enabling more efficient, reliable, and automated quality control.

cs.CV↗

arXiv2025

MID-INFRARED (MIR) OCT-based inspection in industry

This paper aims to evaluate mid-infrared (MIR) Optical Coherence Tomography (OCT) systems as a tool to penetrate different materials and detect sub-surface irregularities. This is useful for monitoring production processes, allowing Non-Destructive Inspection Techniques of great value to the industry. In this exploratory study, several acquisitions are made on composite and ceramics to know the capabilities of the system. In addition, it is assessed which preprocessing and AI-enhanced vision algorithms can be anomaly-detection methodologies capable of detecting abnormal zones in the analyzed objects. Limitations and criteria for the selection of optimal parameters will be discussed, as well as strengths and weaknesses will be highlighted.

eess.IV↗

arXiv2019

Influence of the Cathodes Microstructure on the Stability of Inverted Planar Perovskite Solar Cells

One of the main challenges for perovskite solar cells (PSC) is their stability, due to environment-induced perovskite decomposition. The resulting decomposition compounds are mobile and may, therefore, react with charge carrier extraction layers or the contact metallization, in addition to enhancing the recombination rate in the absorber layer. In this contribution, the influence of different contact metallization layers, such as aluminum (Al), silver (Ag), gold (Au) and nickel (Ni) on the storage stability of inverted planar methylammonium lead iodide (MAPI)-based perovskite solar cells without encapsulation has been investigated. For this study current-voltage (J-V) and impedance measurements in combination with scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDX) analysis were used to examine and correlate structural device information with the development of PSC electrical properties. While a strong perovskite decomposition and further iodide diffusion to the contacts were detected for devices using Al, Ag or Au as cathode electrodes, the microstructure of Ni cathodes inhibits such decomposition process. This experiment has allowed for the realization of MAPI based solar cells with Ni contacts, which exhibit no efficiency decrease below as-fabricated values for up to one month of storage and select AM1.5 testing in ambient atmosphere.

physics.app-ph↗

arXiv2013

Laser-Doping of Crystalline Silicon Substrates using Doped Silicon Nanoparticles

Crystalline Si substrates are doped by laser annealing of solution processed Si. For this experiment, dispersions of highly B-doped Si nanoparticles (NPs) are deposited onto intrinsic Si and laser processed using an 807.5nm cw-laser. During laser processing the particles as well as a surface-near substrate layer are melted to subsequently crystallize in the same orientation as the substrate. The doping profile is investigated by secondary ion mass spectroscopy revealing a constant B concentration of 2x10^18 cm^-3 throughout the entire analyzed depth of 5μm. Four-point probe measurements demonstrate that the effective conductivity of the doped sample is increased by almost two orders of magnitude. The absolute doping depth is estimated to be in between 8μm and 100μm. Further, a pn-diode is created by laser doping an n-type c-Si substrate using the Si NPs.

cond-mat.mtrl-sci↗

arXiv2012

Reduced Coulomb interaction in organic solar cells by the introduction of inorganic high-k nanostructured materials

In this article a concept is introduced, which allows for reduced Coulomb interaction in organic solar cells and as such for enhanced power conversion efficiencies. The concept is based on the introduction of electrically insulating, nanostructured high-k materials into the organic matrix, which do not contribute to the charge transport, however, effectively enhance the permittivity of the organic active layer and thereby reduce the Coulomb interaction. Using an analytical model it is demonstrated that even at a distance of 20 nm to the organic / inorganic interface of the nanostructure, the Coulomb interaction can be reduced by more than 15 %. The concept is implemented using P3HT:PCBM solar cells with integrated high-k nanoparticles (strontium titanate). It could be demonstrated that in comparison to a reference cell without integrated nanoparticles, the power conversion efficiencies could be improved by ~20 %.

cond-mat.mtrl-sci↗