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Uncertainty estimation and design optimization of 2D diffraction-based overlay metrology targets
Get PDFScatterometry is an optical metrology technique, in which light scattered from a specifically designed grating stack (overlay target) is measured in the far-field. Using 1D periodic overlay target designs the technique has been shown to have nanometer-scale sensitivity to spatial misalignments of subsequent patterned layers, which are also known as overlay errors. However, while scatterometry is highly sensitive to overlay errors, multiple sources of systematic errors hinder its absolute accuracy. Here, we investigate how an extended version of scatterometry called Fourier scatterometry in combination with more complex overlay target designs can help addressing those challenges. To this end, we developed a statistical method, which can determine the influence of 2D overlay targets on the overlay measurement uncertainty. We study periodic and deterministic aperiodic designs as well as designs that emerged from simulated annealing optimizations. Our results suggest that current overlay target designs could be augmented by more complex 2D designs to fulfill specific purposes, such as fabrication robustness and high sensitivity over a large overlay range
Using Hot Electrons and Hot Holes for Simultaneous Cocatalyst Deposition on Plasmonic Nanostructures
Get PDFHot electrons generated in metal nanoparticles can drive chemical reactions and selectively deposit cocatalyst materials on the plasmonic hotspots, the areas where the decay of plasmons takes place and the hot electrons are created. While hot electrons have been extensively used for nanomaterial formation, the utilization of hot holes for simultaneous cocatalyst deposition has not yet been explored. Herein, we demonstrate that hot holes can drive an oxidation reaction for the deposition of the manganese oxide (MnOx) cocatalyst on different plasmonic gold (Au) nanostructures on a thin titanium dioxide (TiO2) layer, excited at their surface plasmon resonance. An 80% correlation between the hot-hole deposition sites and the simulated plasmonic hotspot location is showed when considering the typical hot-hole diffusion length. Simultaneous deposition of more than one cocatalyst is also achieved on one of the investigated plasmonic systems (Au plasmonic nanoislands) through the hot-hole oxidation of a manganese salt and the hot-electron reduction of a platinum precursor in the same solution. These results add more flexibility to the use of hot carriers and open up the way for the design of complex photocatalytic nanostructures
Thermodynamic Stabilization of Mixed-Halide Perovskites against Phase Segregation
Get PDFMixing iodide and bromide in halide perovskite semiconductors is an effective strategy to tune their band gap; therefore, mixed-halide perovskites hold great promise for color-tunable LEDs and tandem solar cells. However, the band gap of mixed-halide perovskites is unstable under (sun-)light, since the halides segregate into domains of different band gaps. Using pressure-dependent ultrafast transient absorption spectroscopy, we find that high external pressure increases the range of stable halide mixing ratios. Chemical compression, by inserting a smaller cation, has the same effect, which means that any iodide:bromide ratio can be stabilized by tuning the crystal volume and compressibility. We interpret these findings as an increased thermodynamic stabilization through alteration of the Gibbs free energy via the largely overlooked PΔV term
A simple transfer-matrix model for metasurface multilayer systems
Get PDFIn this work we present a simple transfer-matrix based modeling tool for arbitrarily layered stacks of resonant plasmonic metasurfaces interspersed with dielectric and metallic multilayers. We present the application of this model by analyzing three seminal problems in nanophotonics. These are the scenario of perfect absorption in plasmonic Salisbury screens, strong coupling of microcavity resonances with the resonance of plasmon nano-antenna metasurfaces, and the hybridization of cavities, excitons and metasurface resonances
Generation of pure OAM beams with a single state of polarization by antenna-decorated microdisk resonators
Get PDFWe report waveguide-addressed plasmonic–photonic resonators that generate beams of controlled orbital angular momentum and spin angular momentum content upon driving through a waveguide. From phase-gradient metasurfaces, we borrow the idea of carefully combining multiple nanoscale resonators in a repeat unit, from which we build periodic rings that decorate microdisk resonators. We describe the general mode structure of microdisk cavities perturbed by antenna arrays on the basis of a quasinormal mode formalism and present a strategy to simultaneously control the orbital and spin angular momentum content of light outcoupled to the far field. We propose a realization that uses silicon nitride disks and aluminum nanorod antennas. We find excellent polarization and orbital angular momentum (OAM) purity, as benchmarked by polarization-resolved interferometric Fourier microscopy on single devices
Glancing at tiny vibrations: backaction evading measurements of mechanical motion close to the quantum regime
No full textMeasurement plays a central role in quantum theory. This thesis explores fundamental and practical limits to the sensitivity of measurements of the mechanical motion of a macroscopic object. Optical measurements of mechanical motion are at the core of the research efforts in this thesis. Extremely sensitive optomechanical measurements can be performed in systems in which a mechanical vibrational mode is co-localized with an optical cavity field. In this work we perform measurements on sliced nanobeam photonic crystal cavities, that operate in the regime in which the mechanical frequency is smaller than the optical cavity line width and exhibit large photon-phonon coupling strength
Nanophotonic emission control for improved photovoltaic efficiency
Get PDFWith the necessary transition to renewable energy at hand, there is a renewed research focus on increasing solar cell efficiency, in order to reduce the cost of electricity. Nanomaterials are promising candidates to contribute to a new generation of low cost and highly efficient solar cells. Due to their wavelength-scale dimensions, nanomaterials display exceptionally strong light-matter interactions that lead to large perturbations in absorption and emission compared to their bulk counterparts. Although most work on nanostructured solar cells has focused on increasing the absorption, emission control may have even greater potential for improving efficiency of state-of-the-art solar cells. In this perspective article, we describe how nanostructures can be applied to improve solar cell efficiency, focusing on emission control. First, we analyze the requirements for making the most efficient solar cell, by looking at the thermodynamics of energy conversion. We show that an ideal solar cell at open circuit displays emission that is identical to its absorption. Comparing this to the emission of a typical silicon solar cell shows that there are three differences: the intensity, the angles in which light is emitted, and the spectrum. These differences lead to a reduction in efficiency, mainly due to a drop in open circuit voltage. For each loss mechanism, we discuss how nanomaterials can manipulate the emission and thereby reduce the voltage loss. Finally, we analyze the performance of two conceptual designs for solar cells based on nanomaterials. These give a large improvement in efficiency compared to conventional designs, showing the great potential of nanomaterials in solar cells
Peptide Side-COOH Groups Have Two Distinct Conformations under Biorelevant Conditions
Get PDFThe carboxyl (COOH) side chain groups of amino acids, such as aspartic acid, play an important role in biochemical processes, including enzymatic proton transport. In many theoretical studies, it was found that the (bio)chemical reactivity of the carboxyl group strongly depends on the conformation of this group. Interestingly, up to now there has been no experimental investigation of the geometry and the stability of different COOH conformers under biorelevant conditions. Here, we investigate the conformational isomerism of the side chain COOH group of N-acetyl aspartic acid amide using polarization-resolved two-dimensional infrared spectroscopy. We find that the carboxyl group shows two distinct near-planar conformers (syn and anti) when dissolved in water at room temperature. Both conformers are significantly populated in aqueous solution (75 ± 10% and 25 ± 10% for syn and anti, respectively). Molecular dynamics simulations show that the anti conformer interacts more strongly with water molecules than the syn conformer, explaining why this conformer is significantly present in aqueous solution
Mechanisms of motor-independent membrane remodeling driven by dynamic microtubules
Get PDFMicrotubule-dependent organization of membranous organelles occurs through motor-based pulling and by coupling microtubule dynamics to membrane remodeling. For example, tubules of endoplasmic reticulum (ER) can be extended by kinesin- and dynein-mediated transport and through the association with the tips of dynamic microtubules. The binding between ER and growing microtubule plus ends requires End Binding (EB) proteins and the transmembrane protein STIM1, which form a tip-attachment complex (TAC), but it is unknown whether these proteins are sufficient for membrane remodeling. Furthermore, EBs and their partners undergo rapid turnover at microtubule ends, and it is unclear how highly transient protein-protein interactions can induce load-bearing processive motion. Here, we reconstituted membrane tubulation in a minimal system with giant unilamellar vesicles, dynamic microtubules, an EB protein, and a membrane-bound protein that can interact with EBs and microtubules. We showed that these components are sufficient to drive membrane remodeling by three mechanisms: membrane tubulation induced by growing microtubule ends, motor-independent membrane sliding along microtubule shafts, and membrane pulling by shrinking microtubules. Experiments and modeling demonstrated that the first two mechanisms can be explained by adhesion-driven biased membrane spreading on microtubules. Optical trapping revealed that growing and shrinking microtubule ends can exert forces of ∼0.5 and ∼5 pN, respectively, through attached proteins. Rapidly exchanging molecules that connect membranes to dynamic microtubules can thus bear a sufficient load to induce membrane deformation and motility. Furthermore, combining TAC components and a membrane-attached kinesin in the same in vitro assays demonstrated that they can cooperate in promoting membrane tubule extension