Browsing by Subject "SiO2"

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    ItemOpen Access
    Low dark current N structure superlattice MWIR photodetectors
    (SPIE, 2014) Salihoğlu, O.; Muti, Abdullah; Turan, R.; Ergun, Y.; Aydınlı, Atilla
    Commercially available read out integrated circuits (ROICs) require the FPA to have high dynamic resistance area product at zero bias (R0A) which is directly related to dark current of the detector. Dark current arises from bulk and surface contributions. Recent band structure engineering studies significantly suppressed the bulk contribution of the type-II superlattice infrared photodetectors (N structure, M structure, W structure). In this letter, we will present improved dark current results for unipolar barrier complex supercell superlattice system which is called as "N structure". The unique electronic band structure of the N structure increases electron-hole overlap under bias, significantly. N structure aims to improve absorption by manipulating electron and hole wavefunctions that are spatially separated in T2SLs, increasing the absorption while decreasing the dark current. In order to engineer the wavefunctions, we introduce a thin AlSb layer between InAs and GaSb layers in the growth direction which also acts as a unipolar electron barrier. Despite the difficulty of perfect lattice matching of InAs and AlSb, such a design is expected to reduce dark current. Experiments were carried out on Single pixel with mesa sizes of 100 × 100 - 700 × 700 μm photodiodes. Temperature dependent dark current with corresponding R0A resistance values are reported.
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    ItemOpen Access
    NaCl-promoted CuO–RuO2/SiO2 catalysts for propylene epoxidation with O2 at atmospheric pressures: a combinatorial micro-reactor study
    (Springer, 2015) Kalyoncu, Ş.; Düzenli, D.; Onal, I.; Seubsai, A.; Noon, D.; Senkan, S.; Say, Z.; Vovk, E. I.; Ozensoy, E.
    A combinatorial approach is used to investigate several alkali metals promoted Cu–Ru binary oxide catalysts with improved catalytic performance in the propylene partial oxidation. 2 %Cu/5 %Ru/c–SiO2 catalyst had the best yield with high propylene conversion and propylene oxide (PO) selectivity. Among the promoters screening in the study, NaCl promotion significantly increased the PO selectivity accompanied by some attenuation in the total propylene conversion. It was proposed that binary oxide catalysts revealed a greater number of exposed catalytically active adsorption sites as compared to monometallic oxide counterparts according to XPS and FTIR results. Besides NaCl addition alters the structure, yielding a significantly improved PO selectivity without any change in the particle size of Cu and Ru oxide according to XRD analysis.