Ultra-thin metallic films are widely applied in optics and microelectronics. However, their properties differ significantly from the bulk material and depend on the substrate material. The nucleation, film growth, and layer properties of atomic layer deposited (ALD) iridium thin films are evaluated on silicon wafers, BK7, fused silica, SiO₂, TiO₂, Ta₂O₅, Al₂O₃, HfO₂, Ru, Cr, Mo, and graphite to understand the influence of various substrate materials. This comprehensive study was carried out using scanning electron and atomic force microscopy, X-ray reflectivity and diffraction, four-point probe resistivity and contact angle measurements, tape tests, and Auger electron spectroscopy. Within few ALD cycles, iridium islands occur on all substrates. Nevertheless, their size, shape, and distribution depend on the substrate. Ultra-thin (almost) closed Ir layers grow on a Ta₂O₅ seed layer after 100 cycles corresponding to about 5 nm film thickness. In contrast, the growth on Al₂O₃ and HfO₂ is strongly inhibited. The iridium growth on silicon wafers is overall linear. On BK7, fused silica, SiO₂, TiO₂, Ta₂O₅, Ru, Cr, and graphite, three different growth regimes are distinguishable. The surface free energy of the substrates correlates with their iridium nucleation delay. Our work, therefore, demonstrates that substrates can significantly tailor the properties of ultra-thin films.

We report for the first time the direct growth of molybdenum disulfide (MoS ₂ ) monolayers on nanostructured silicon‐on‐insulator waveguides. Our results indicate the possibility of utilizing the Chemical Vapour Deposition (CVD) on nanostructured photonic devices in a scalable process. Direct growth of 2D material on nanostructures rectifies many drawbacks of the transfer‐based approaches. We show that the van der Waals material grow conformally across the curves, edges, and the silicon–SiO ₂ interface of the waveguide structure. Here, the waveguide structure used as a growth substrate is complex not just in terms of its geometry but also due to the two materials (Si and SiO ₂ ) involved. A transfer‐free method like this yields a novel approach for functionalizing nanostructured, integrated optical architectures with an optically active direct semiconductor.

Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially, metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical applications. While noble-metal nanoparticles, nanostructures, and thin films of silver and gold have been widely studied, iridium (Ir) nanoparticles and ultrathin films have not been investigated for nonlinear optical applications yet. Here, we present a combined theoretical and experimental study on the linear and nonlinear optical properties of iridium nanoparticles deposited via atomic layer deposition (ALD). Linear optical constants, such as the effective refractive index and extinction coefficient, were evaluated at different growth stages of nanoparticle formation. Both linear and nonlinear optical properties of these Ir ALD coatings were calculated theoretically using the Maxwell Garnett theory. The third-order susceptibility of iridium nanoparticle samples was experimentally investigated using the z-scan technique. According to the experiment, for an Ir ALD coating with 45 cycles resulting in iridium nanoparticles, the experimentally determined nonlinear third-order susceptibility is about χ_Ir⁽³⁾ = (2.4 − i2.1) × 10⁻¹⁷ m²/V² at the fundamental wavelength of 700 nm. The theory fitted to the experimental results predicts a 5 × 10⁶-fold increase around 230 nm. This strong increase is due to the proximity to the Mie resonance of iridium nanoparticles.

Optical surfaces equipped with specific functional properties have attracted increasing importance over the last decades. In the light of cost reduction, hydrophobic self-cleaning behavior is aspired. On the other side, hydrophilic properties are interesting due to their anti-fog effect. It has become well known that such wetting states are significantly affected by the surface morphology. For optical surfaces, however, this fact poses a problem, as surface roughness can induce light scattering. The generation of optical surfaces with specific wetting properties, hence, requires a profound understanding of the relation between the wetting and the structural surface properties. Thus, our work concentrates on a reliable acquisition of roughness data over a wide spatial frequency range as well as on the comprehensive description of the wetting states, which is needed for the establishment of such correlations. We will present our advanced wetting analysis for nanorough optical surfaces, extended by a vibration-based procedure, which is mainly for understanding and tailoring the wetting behavior of various solid-liquid systems in research and industry. Utilizing the relationships between surface roughness and wetting, it will be demonstrated how different wetting states for hydrophobicity and hydrophilicity can be realized on optical surfaces with minimized scatter losses.

Aluminum thin films with thicknesses between approximately 10 and 60 nm have been deposited by evaporation and sputtering techniques. Layer characterization focused on reflectance, optical constants, and surface quality. Reflectance fits have been performed using a merger of three standard dispersion models, namely the Drude model, the Lorentzian oscillator model, and the beta-distributed oscillator model. A thickness dependence of the optical constants could be established in the investigated thickness range.

Understanding the influence of topography on wettability is essential for improving the modeling of superhydrophobic surfaces. Moreover, wetting predictions can foresee corrosion, biological contamination, self-cleaning properties, and all phenomena related to wetting. In this context, this research work reports the experimental corroboration of a novel theoretical model for stochastic surfaces that relates the static contact angle for the heterogeneous wetting of surfaces to the root mean square (RMS) slope of the surface structures, allowing wetting prediction through topography. For this study, hydrophobic and superhydrophobic alumina thin films with gradual roughness were constructed. The films were deposited on glass using the dip-coating technique, textured with boiling water, and functionalized to achieve low surface energy using Dynasylan F-8815. Surface wettability was characterized using the sessile drop technique, and the RMS slope of the alumina surfaces was quantified using the atomic force microscopy (AFM) technique. The model, presented here for the first time, fits the experimental data, allowing wetting prediction for hydrophobic and superhydrophobic surfaces considering static contact angles. As expected, topography plays a fundamental role in achieving superhydrophobicity. Therefore, defining a topographic criterion, as performed here, for obtaining superhydrophobic surfaces is highly relevant to reduce the production costs of these surfaces and also enable new production processes and designs.