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Studies of crystallization of a sol-gel derived alumina thin film showed on a critical role of spinodal-like wrinkling. The wrinkling that depends on a humidity gradient in the film provides nucleation sites with high supersaturation located at the top of topological islands that occur as a result of the wrinkling. Nucleation of crystal nuclei takes place at these sites at a significantly lower temperature as it would be the case for homogenous nucleation. The crystal growth continues through different supersaturation regimes that are defined by the wrinkling topology. We showed how the crystallization can be efficiently suppressed to higher temperatures by minimizing the humidity gradient in the dip-coated film by controlled drying. [ABSTRACT FROM AUTHOR]

Substantial broadband photoconductive gain has been realized for organic, thin-film photodetectors with a poly(3-hexylthiophene):phenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM) active layer at low bias voltages. External quantum efficiencies upwards of 1500% were achieved when a semicontinuous gold layer was introduced at the anode interface. Significant gain was also observed in the sub-band gap, near infrared region where the external quantum efficiency approached 100% despite the lack of a sensitizer. The gain response was highly dependent on the thickness of the active layer of the photodetector with the best results achieved with the thinnest devices. The gain is the result of the injection of secondary electrons due to hole charge trapping at the semicontinuous gold layer. [ABSTRACT FROM AUTHOR]

We report on the excitation of sharp Fano-like resonances in lattices of metamolecules composed of two differing types of metaatoms. The proposed structures exhibit modes originating from the individual metaatoms as well as a very sharp mode from the collective excitation of the metamolecule lattice as a whole. Next-generation thin film sensors (e.g., for bio/chemical hazard detectors) could especially benefit from such artificial materials. Having multiple modes at different spectral positions enables the characterization of dispersive materials, while the high Q-factors of the eigenmodes lead to a very high sensitivity. [ABSTRACT FROM AUTHOR]