Low-cost direct writing lithography system for the sub-micron range

Abstract

We have developed a fixed beam direct writing laser lithography system with a minimum feature size of 400nm at 457nm wavelength and a writing speed of 4·2mm/s with total system costs of less than 100 000 US$.     

Generalized juntas and NP-hard sets

We show that many NP-hard sets have heuristic polynomial-time algorithms with high probability weight of correctness with respect to generalizations of Procaccia and Rosenschein’s junta distributions.     

Development of new polymer�CBaTiO3-composites with improved permittivity for embedded capacitors

A series of commercially available nanosized barium titanates has been investigated with respect to their use as high-k-ceramic filler in polymer based composites with improved dielectric properties. The thermal treatment of the barium titanate powders at 1,000°C causes a significant increase of the composite’s permittivity. X-ray diffraction experiments prior and after heat treatment revealed that the barium titanate with smallest particle size and the largest specific surface area possesses the thermodynamically unstable cubic phase. In case of the other investigated barium titanates the crystal lattice is distorted. Thermal treatment induces the phase change into the tetragonal one and crystal lattice relaxation enabling higher permittivity values. Composites with a solid load around 78 wt% with a bimodal particle size distribution show high permittivities around 50 and a low loss factor around 5‰ suitable for the realization of embedded capacitors via screen printing or tape casting.     

The mental lexicon is fully specified: Evidence from eye-tracking.

Four visual-world experiments, in which listeners heard spoken words and saw printed words, compared an optimal-perception account with the theory of phonological underspecification. This theory argues that default phonological features are not specified in the mental lexicon, leading to asymmetric lexical matching: Mismatching input (pin) activates lexical entries with underspecified coronal stops (tin), but lexical entries with specified labial stops (pin) are not activated by mismatching input (tin). The eye-tracking data failed to show such a pattern. Although words that were phonologically similar to the spoken target attracted more looks than did unrelated distractors, this effect was symmetric in Experiment 1 with minimal pairs (tin–pin) and in Experiments 2 and 3 with words with an onset overlap (peacock–teacake). Experiment 4 revealed that /t/-initial words were looked at more frequently if the spoken input mismatched only in terms of place than if it mismatched in place and voice, contrary to the assumption that /t/ is unspecified for place and voice. These results show that speech perception uses signal-driven information to the fullest, as was predicted by an optimal perception account. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Fullerene Single Crystals: Structure and Electronic Properties

Abstract

This work covers an advanced investigation of the single crystal growth process for fullerenic materials and the contribution of Raman and IR spectroscopy to the understanding of the fcc high temperature rotor phase and the low temperature sc ratchet phase of pristine C₆₀. In addition substantial research contributions to the understanding of alkali metal doped fullerenes are presented.

Alkali metal doped crystals are studied with particular attention to the line broadening in the superconducting A ₃C₆₀ phase and to the phases with stoichiometry A₁C₆₀. For the former electron-phonon coupling constants could be determined for all fivefold degenerated gerade modes and a total coupling strenght of λ = 0.90 was found. For the latter the different experimental conditions for obtaining the phase separated intermediate state or alternatively the orthorhombic polymeric state are analysed. Vibrational spectra for the polymeric state obtained from phototransformation and from mono alkali metal doping are found to be characteristically different, mainly with respect to the intensity of the Raman or IR response. Finally, research results obtained from the single crystals by various other techniques like thermal expansion or low frequency elastic deformation are summarized.     

Switchable Plasmonic Metasurface Utilizing the Electro-Optic Kerr Effect of a Blue Phase Liquid Crystal

A switchable metasurface composed of plasmonic split ring resonators and a polymer-stabilized liquid crystal blue phase is developed. Owing to field-induced birefringence (electro-optic Kerr effect), the state of polarization of the incident near infrared radiation changes, when a voltage is applied to the liquid crystal. Thus, different resonant modes of the split ring resonators can be addressed and the transmission spectrum changes accordingly. In comparison with other liquid crystal phases, blue phases have several advantages. For example, they are optically isotropic in the field-off state, so that no alignment layer is required. The results of the present study indicate that the advantages of these mesophases can be utilized for switchable metasurfaces.