Vapor-solvent shift of the lowest frequency vibration of p-benzoquinone and toluquinone and the consequences for the vibrational and electronic spectral assignments

Far-infrared (20–230 cm–1) absorption spectra of p-benzoquinone-h4,-d4 and of toluquinone have been measured. In the vapor phase, the lowest frequency vibration of these three compounds is found at 88.9, 87.5, and 82.3 cm–1, respectively. In the condensed phase the frequency increases by approximately 20 cm–1. These measurements clarify assignments, based on this vibrational mode, of the visible absorption spectrum as well as of other vibrations. It is proposed that intermolecular forces are responsible for the large frequency shift and that the observed width in solution (≈24 cm–1) is homogeneous, reflecting rapid relaxation processes of this large amplitude low frequency bending mode

Order quantification of hexagonal periodic arrays fabricated by in situ solvent-assisted nanoimprint lithography of block copolymers

arXiv:1403.2250v1Directed self-assembly of block copolymer polystyrene-b-polyethylene oxide (PS-b-PEO) thin film was achieved by a one-pot methodology of solvent vapor assisted nanoimprint lithography (SAIL). Simultaneous solvent-anneal and imprinting of a PS-b-PEO thin film on silicon without surface pre-treatments yielded a 250 nm line grating decorated with 20 nm diameter nanodots array over a large surface area of up to 4' wafer scale. The grazing-incidence small-angle x-ray scattering diffraction pattern showed the fidelity of the NIL stamp pattern replication and confirmed the periodicity of the BCP of 40 nm. The order of the hexagonally arranged nanodot lattice was quantified by SEM image analysis using the opposite partner method and compared to conventionally solvent-annealed block copolymer films. The imprint-based SAIL methodology thus demonstrated an improvement in ordering of the nanodot lattice of up to 50%, and allows significant time and cost reduction in the processing of these structures.The research leading to these results received funding from the European Union FP7 under the project LAMAND (grant agreement n° 245565), NANOFUNCTION (grant agreement no. 257375, FP7-ICT-2009-5) and by the Spanish Ministry of Economics and Competitiveness under project TAPHOR contract no. MAT2012-31392 (Plan Nacional de I + D + I (2008–2011)Peer Reviewe

Terahertz thermometry: combining hyperspectral imaging and temperature mapping at terahertz frequencies

The accurate and non-invasive determination of multiple physical parameters, with well-defined spatial resolution, is crucial for applications in manufacturing, chemistry, medicine and biology. Specifically, the ability to simultaneously measure both temperature and spectral signatures is still experimentally unavailable. To this end, we propose a mapping technique for biological systems, which exploits a linear correlation between terahertz wave reflectivity and temperature, and allows to spatially and spectrally resolve thermal distributions. This method is applied to a model biological system in two relevant cases where in one example, nanoplasmonic-induced photothermal effects are imaged gaining new insights into collective heating phenomena. In the second example, we demonstrate a joint thermal-hyperspectral imaging approach to chemically map the presence of a model drug formulation and simultaneously investigate its thermal stability in our biological system. This concept can be easily extended and widely applied to all materials that demonstrate a measurable change in their dielectric properties

Order quantification of hexagonal periodic arrays fabricated by in situ solvent-assisted nanoimprint lithography of block copolymers

Directed self-assembly of block copolymer polystyrene-b-polyethylene oxide (PS-b-PEO) thin film was achieved by one-pot methodology of solvent vapour assisted nanoimprint lithography (SAIL).Comment: 12 pages, 4 figures, paper accepte

Surface-directed dewetting of a block copolymer for fabricating highly uniform nanostructured microdroplets and concentric nanorings

Through a combination of nanoimprint lithography and block copolymer self-assembly, a highly regular dewetting process of a symmetric diblock copolymer occurs whereby the hierarchal formation of microdroplets and concentric nanorings emerges. The process is driven by the unique chemical properties and geometrical layout of the underlying patterned silsesquioxane micrometer-sized templates. Given the presence of nonpreferential substrate−polymer interactions, directed dewetting was utilized to produce uniform arrays of microsized droplets of microphase separated polystyrene-block-poly(methyl methylacrylate) (PS-b-PMMA), following thermal annealing at 180 °C. Microdroplets with diameters greater than 400 nm exhibited a hexagonal close-packed arrangement of nanodots on the surface with polydomain ordering. At the droplet periphery, the polydomain ordering was severely disrupted because of a higher in-plane radius of curvature. By reducing the droplet size, the in-plane radius of curvature of the microdroplet becomes significant and the PMMA cylinders adopt parallel structures in this confined geometry. Continuous scaling of the droplet results in the generation of isolated, freestanding, self-aligned, and self-supported oblique nanorings (long axis ∼250−350 nm), which form as interstitial droplets between the larger microdroplets. Optical and magnetic-based nanostructures may benefit from such hierarchal organization and self-supporting/aligned nanoring templates by combining more than one lithography technique with different resolution capabilities

Spontaneous emission control of colloidal nanocrystals using nanoimprinted photonic crystals

The authors report on the fabrication and optical characterizations of two-dimensional photonic crystals fabricated by nanoimprint lithography in a nanocomposite polymer incorporating highly luminescent and red emitting (CdSe)ZnS core-shell colloidal nanocrystals. Photonic crystal structures enhance the light emitted from the quantum sized nanoparticles in the composite layer by slowing the propagation speed of the photons, thus increasing the coupling to the out-of-plane radiative modes. A 200% enhancement of the light collection is achieved compared to an unpatterned sample. (c) 2007 American Institute of Physics. (DOI:10.1063/1.2430625

Lithographically Defined Cross-Linkable Top Coats for Nanomanufacturing with High-χ Block Copolymers

The directed self-assembly (DSA) of block copolymers (BCPs) is a powerful method for the manufacture of high-resolution features. Critical issues remain to be addressed for successful implementation of DSA, such as dewetting and controlled orientation of BCP domains through physicochemical manipulations at the BCP interfaces, and the spatial positioning and registration of the BCP features. Here, we introduce novel top-coat (TC) materials designed to undergo cross-linking reactions triggered by thermal or photoactivation processes. The cross-linked TC layer with adjusted composition induces a mechanical confinement of the BCP layer, suppressing its dewetting while promoting perpendicular orientation of BCP domains. The selection of areas of interest with perpendicular features is performed directly on the patternable TC layer via a lithography step and leverages attractive integration pathways for the generation of locally controlled BCP patterns and nanostructured BCP multilayers

Nanoscale patterning using imprint lithographies

National audienc

Cristaux photoniques en silicium sur isolant pour le guidage, le filtrage, l'émission et l'éxtraction de lumière

Photonic crystals (PCs), i.e. periodic dielectric structures, allow the control of light. For example, propagation of photons can be suppressed in certain directions and for frequencies contained in what is called the photonic band gap (PBG). This thesis report on the conception, fabrication and characterization of guides, filters, planar micro-cavities and light extractors based on two-dimensional silicon photonic crystals. This structures can be etched in the planar waveguide of silicon-on-insulator (SOI) substrates and they can take advantage of well known microelectronic fabrication technology. Furthermore, the fabrication with CMOS-type technology on 8 in. wafers allows to prepare the integration of optical functions within silicon microelectronic chips. The first part of this manuscript focuses on passive structures: guides and filters. An original optical bench was build in order to perform transmission measurements on a wide wavelength range (1.1 to 1.7 µm). Monolayer waveguides, mirrors and unidimensional cavities are investigated. Resonant modes with quality factors higher than 150 are measured. This results are in very good agreement with the FDTD (Finite Difference Time Domain) simulations and with the calculated band diagrams. The second part of the thesis concerns the out-of-plane light emission from photonic crystal structures. Confinement of photons in planar micro-cavities and light extraction properties of particular points on the photonic crystal band diagram are studied. Both approaches are investigated on SOI substrates and on a new kind of substrates, called “optical substrates”, developed especially for our applications and composed of a monocrystalline silicon layer bonded a buried distributed Bragg reflector. That way, the influence of the light confinement in the third direction have been investigated. On SOI substrate, a light extraction efficiency higher than 45 % have been measured on one side and in a reduced solid angle.Les cristaux photoniques sont des structures diélectriques périodiques. Ils permettent de contrôler la lumière en interdisant, par exemple, la propagation des photons dans certaines directions et pour certaines fréquences contenues dans ce que l'on appelle le gap photonique. De part leur compatibilité avec la filière silicium et leur relative simplicité de fabrication, les cristaux photoniques bidimensionnels réalisés sur substrats silicium-sur-isolant (SOI) sont particulièrement attractifs pour la fabrication de circuits intégrés photoniques et ils pourraient constituer la base des futures interconnexions optiques en microélectronique. Dans ce cadre, nous nous sommes intéressé à la conception, la fabrication et la caractérisation de guides d'onde, de filtres, de cavités planaires et d'extracteurs de lumière. Dans une première partie, nos efforts se sont portés sur les structures passives. Un banc d'optique original à été monté pour caractériser celles-ci en optique guidé sur un large plage de longueur d'onde (de 1,1 à 1,7 µm). Le guidage dans des guides à cristaux photoniques mono-rangée a été caractérisé spectralement et la transmittance de miroirs et de cavités unidimensionnelles à cristaux photoniques a été étudiée. Des modes résonnants avec des facteurs de qualité jusqu'à 150 ont été mesurés. Ces résultats sont en très bon accord avec les simulations menées par la technique FDTD (Finite Difference Time Domain) et avec les calculs de diagrammes de bandes obtenus par la méthode des ondes planes. Dans un second temps, nous avons regardé les propriétés de photoluminescence hors du plan de certaines structures à cristaux photoniques. Deux voies différentes sont explorées : le confinement des photons dans le plan à l'aide de cavités hexagonales et l'utilisation de propriétés particulières de dispersion de certains modes du cristal photonique pour extraire la lumière. Ces deux approches sont abordées parallèlement sur des substrats SOI et sur de nouveaux substrats, appelés « substrats optiques », développés spécialement pour nos applications et constitués d'un guide planaire en silicium monocristallin déposé sur un miroir diélectrique multicouche. Ainsi, l'influence du confinement dans la direction verticale est abordée. Pour les extracteurs de lumière sur substrat SOI, une efficacité d'extraction de plus de 45 % est mesurée sur une face et dans un angle solide réduit