PVD solutions for automotive thin film applications

As automotive lighting is in the transition from a simple combination of an incandescent light bulb with beam shaping reflective surfaces towards quite complex headlamps equipped white matrix LED in combination with transmission optics, the requirements to achieve a high efficiency also changed. While the former headlamps require a high reflectance, the latter design gains a high efficiency via a maximized transmittance. In addition, new challenges arise due to an increasing amount of cameras, new components like Lidar and sensors for driving safety in modern as well as future autonomous driving cars. Physical vapour deposition (PVD) thin film technologies are able to produce coatings for the previously mentioned applications but also offer extraordinary upside potential for future sensor technologies.     

Limitations of the Tauc Plot Method

The Tauc plot is a method originally developed to derive the optical gap of amorphous semiconductors such as amorphous germanium or silicon. By measuring the absorption coefficient α(hν) and plotting ${(\alpha hv)}^{\frac{1}{2}}$ versus photon energy hν, a value for the optical gap (Tauc gap) is determined. In this way non-direct optical transitions between approximately parabolic bands can be examined. In the last decades, a modification of this method for (poly-) crystalline semiconductors has become popular to study direct and indirect interband transitions. For this purpose, (ahν)ⁿ (n = $\frac{1}{2}$, 2) is plotted against hν to determine a value of the electronic bandgap. Due to the ease of performing UV–vis measurements, this method has nowadays become a standard to analyze various (poly-) crystalline solids, regardless of their different electronic structure. Although this leads partially to widely varying values of the respective bandgap of nominally identical materials, there is still no study that critically questions which peculiarities in the electronic structure prevent a use of the Tauc plot for (poly-) crystalline solids and to which material classes this applies. This study aims to close this gap by discussing the Tauc plot and its limiting factors for exemplary (poly-) crystalline solids with different electronic structures.     

Kupfer,Silber, Gold; fixiert in metallorganischen π-Pinzetten

Alkinyl functionalized titanocenes of general type RC≡C-[Ti]-C≡CR and Cl-[Ti]-C≡CR {[Ti] = (η⁵-C₅H₄-SiMe₃)₂Ti}; R = singly bonded organic ligand} can successfully be used as organometallic π-tweezers to stabilize numerous mononuclear MX/R¹ species (M = Cu, Ag, Au; X = singly bonded inorganic group; R¹ = singly bonded organic ligand). The synthesis, manifold reaction chemistry as well as bonding and spectroscopy of {[Ti](C≡CR)₂}MX/R¹ and {[Ti] (C≡CR)(Cl)}CuX complexes is described     

Hexaazapolycyclen durch selektive Multimethylenierungen mit Dichlormethan und Base oder mit Urotropin

Hexaazapolycycles by Selective Multimethylenations with Dichloromethane and Base or with Hexamethylenetetramine Multiple methylenations of 2-aminomethylbenzimidazole with dichloromethane and methylamine or ammonia or with hexamethylenetetramine lead to highly selective formations of 6 new single bonds to give only a polycyclic bis-spiro-1,5-diazocine 2 or only a polycyclic spiro-1,3,6-triazonine 4 or only a polycyclic 1,3,6,8-tetrazecine derivative 6 . 4 and 6 may be equally well obtained starting with 2-chloromethyl-benzimidazole. All of these selectively formed products are concave cryptands with 6 amino nitrogen atoms. No template metals are used in their syntheses. The reasons for the unusual changes in selectivity are investigated using semi-empirical PM3 calculations and mechanistic considerations. Experimental and spectroscopic details are given.     

Photochemische Reaktionen von Pyrazolidon-(3)-betainen. VII. Photochemische Dimerisierung von Pyrazolidon-(3)-azomethiniminen

Photochemical Reactions of 3-Pyrazolidone Betains. VII. Photochemical Dimerization of 3-Pyrazolidone Azomethinimines UV irradiation of 3-pyrazolidone azomethinimines 1 in methanol results in low yields in photochemical head-tail-dimerization of 1 to the hexahydrotetrazines 3 . The structure of 3 is elucidated by chemical and spectroscopic methods (IR, ¹H-, ¹³NMR).     

Detection of Radicals at the Photolysis of tert-Butyl Hydroperoxide in DMSO and water

The decomposition of tert-butyl hydroperoxide by photochemically induced reactions in DMSO

1 Abbreviations used: DMSO, dimethyl sulfoxide; DMSO-d₆, completely deuterium labelled dimethyl sulfoxide; cw-ESR, continuous-wave Electron Spin Resonance; u. v., ultra violet; DMPO, 5, 5-dimethyl-I-pyrroline N-oxide; TMPO, 3, 3, 5, 5-tetramethyl-l-pyrroline N-oxide.

and water was investigated by cw-e.s.r. spectroscopy. The products tert-butylperoxyl, methyl and sulfur-centered free radicals were identified. The tert-butoxyl free radical is involved in the primary process as shown by time-resolved e.s.r. technique. On the basis of directly identified radical species, a mechanism for the photochemically induced reactions of tert-butyl hydroperoxide in DMSO is proposed. At concentrations below 0.8 mol · l⁻¹ the radical formation from tert-butyl hydroperoxide proceeds by cleavage of the O O bond rather than by hydrogen abstraction.     

Abfallfreie Gas/Festkörper-Diazotierung mit Stickstoffdioxid und quantitative Triazensynthese ohne Flüssigphase

Waste-Free Quantitative Gas/Solid Diazotation Using Nitrogen Dioxide and Triazene Synthesis, Both Avoiding Liquid Phases Solid diazonium nitrates (2a–j) are quantitatively obtained by reaction of crystalline anilines (1a–j) with gaseous nitrogen dioxide. Solid diazonium salts react quantitatively with dimethylamine to give the triazenes (4a–j) . Wastes that are typical for the previous syntheses of these compounds in solution are avoided. Atomic force microscopic (AFM) investigations indicate long-range molecular movements due to phase rebuilding. The features thus formed are related to the known crystal structures of the starting anilines. The diazotations run to completion, because, after accumulation of product molecules, phase transformation to give the product lattices leads to crystal disintegration and thus to formation of fresh surface over and over.