defined polarization state is a key requirement in numerous photonic applications. For example, linear optical polarizers are frequently utilized in lithography, [7,8] industrial vision, [9] microscopy, ellipsometry [10] or astronomic remote sensing systems. [11] All these applications substantially benefit from efficient nano-optical wire grid polarizers.A wire grid polarizer (WGP) is a grating type metasurface (see Figure 1). The typical operation principle for such elements requires the transmittance of TM polarized light T TM (TM transversal magneticelectrical field orthogonal to the ridges) to be much larger than that of TE polarized light T TE (transversal electric-electrical field parallel to the ridges) to achieve a significant anisotropic filter functionality. Here, the extinction ratio E r = T TM /T TE is used to express the suppression of TE polarized light. [12] WGPs are highly beneficial because of large achievable element sizes (wafer size), compactness (wafer thickness), and large acceptance angles. [13] Furthermore, their nano-optical nature allows an easy integration into other (nano-)optical elements, such as litho graphy masks, [14] enabling local polarization control. Currently, applications advance toward shorter wavelengths in order to benefit from smaller foci and characteristic electronic transitions, which can be utilized for material analysis. While WGPs are well established in the VIS and IR, suitable ones were not available in the deep ultraviolet (DUV) spectral range until very recently. [12,15,16] The lack of applicable DUV WGPs originates from challenging requirements on both structure and material properties.A structural period of the polarizer has to fulfilling the zero order conditionto avoid propagation of diffraction orders greater than the zeroth one.[17] For a normal incidence of light (ϕ = 0°) with a wavelength λ in the DUV and a fused silica substrate with a refractive index n sub a period p in the order of 100 nm is necessary. Additionally, an aspect ratio (see Figure 1: ratio of height and ridge width) larger than five is typically required. [12] The simultaneous realization of large aspect ratio and small periods is technologically extremely challenging. Fortunately however, advances in nanotechnology do allow the fabrication of such structures. [18] Pelletier et al. [15] demonstrated aluminum WGPsWire grid polarizers (WGPs), periodic nano-optical metasurfaces, are convenient polarizing elements for many optical applications. However, they are still inadequate in the deep ultraviolet spectral range. It is shown that to achieve high performance ultraviolet WGPs a material with large absolute value of the complex permittivity and extinction coefficient at the wavelength of interest has to be utilized. This requirement is compared to refractive index models considering intraband and interband absorption processes. It is elucidated why the extinction ratio of metallic WGPs intrinsically humble in the deep ultraviolet, whereas wide bandgap semiconductors are superior materia...

The electronic and molecular structure of N,N,N',N'-tetraphenylphenylenediamine radical cation 1(+) is in focus of this study. Resonance Raman experiments showed that at least eight vibrational modes are strongly coupled to the optical charge resonance band which is seen in the NIR. With the help of a DFT-based vibrational analysis, these eight modes were assigned to symmetric vibrations. The contribution of these symmetric modes to the total vibrational reorganization energy is dominant. These findings are in agreement with the conclusions from a simple two-state two-mode Marcus-Hush analysis which yields a tiny electron-transfer barrier. The excellent agreement of the X-ray crystal structure analysis and the DFT computed molecular structure of 1(+) on one hand as well as the solvent and solid-state IR spectra and the DFT-calculated IR active vibrations on the other hand prove 1(+) adopts a symmetrical delocalized Robin-Day class III structure both in the solid state and in solution.

Oxide and nitride thin-films of Ti, Hf, and Si serve numerous applications owing to the diverse range of their material properties. It is therefore imperative to have proper control over these properties during materials processing. Ion-surface interactions during plasma processing techniques can influence the properties of a growing film. In this work, we investigated the effects of controlling ion characteristics (energy, dose) on the properties of the aforementioned materials during plasma-enhanced atomic layer deposition (PEALD) on planar and 3D substrate topographies. We used a 200 mm remote PEALD system equipped with substrate biasing to control the energy and dose of ions by varying the magnitude and duration of the applied bias, respectively, during plasma exposure. Implementing substrate biasing in these forms enhanced PEALD process capability by providing two additional parameters for tuning a wide range of material properties. Below the regimes of ion-induced degradation, enhancing ion energies with substrate biasing during PEALD increased the refractive index and mass density of TiOx and HfOx and enabled control over their crystalline properties. PEALD of these oxides with substrate biasing at 150 °C led to the formation of crystalline material at the low temperature, which would otherwise yield amorphous films for deposition without biasing. Enhanced ion energies drastically reduced the resistivity of conductive TiNx and HfNx films. Furthermore, biasing during PEALD enabled the residual stress of these materials to be altered from tensile to compressive. The properties of SiOx were slightly improved whereas those of SiNx were degraded as a function of substrate biasing. PEALD on 3D trench nanostructures with biasing induced differing film properties at different regions of the 3D substrate. On the basis of the results presented herein, prospects afforded by the implementation of this technique during PEALD, such as enabling new routes for topographically selective deposition on 3D substrates, are discussed.