Browsing by Subject "Shape control"

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    A novel hierarchical coding scheme based on polar mass distribution
    (IEEE, 1994) Öktem, Levent; Onural, Levent
    A novel method for coding arbitrarily shaped binary objects is presented. The main idea is expressing the binary object in terms of radial closed curves, that is, closed curves for which radius versus angle is a function. These functions and the simple rules for combining them uniquely represent the object. The data compaction property of the method and the flexibility of the introduced loss are shown. Experimental results are presented, with a comparison to G3 fax standard. Possible application areas are discussed.
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    Shape and deposition angle control of silver film-over-nanosphere SERS substrates
    (Institute of Physics Publishing, 2021-10-06) Esmaeilzad, Nasim Seyedpour; Demirtaş, Özge; Demir, Ahmet Kemal; Bek, Alpan
    Thin metallic films on dielectric nanospheres are demonstrated to have a high potential for the fabrication of cost-effective SERS substrates. In addition to the morphological advantages that nanospheres offer for attaining a high density of hot spots, possessing shape adjustability by uncomplicated thermal treatment makes them an attractive platform for tuneable SERS substrates. Furthermore, when combined with the oblique angle metal deposition technique, adjustable gaps at a high density and adjustable shape of metal films, such as Ag films, can be achieved on nanospheres. Applying small changes in deposition angle can provide means for fine adjustment of the Raman enhancement factor (EF), resulting in EF up to 108 measured using crystal violet dye molecule as a Raman analyte. This practice paves the way for the fabrication of high EF SERS substrates at a reasonable cost using a monolayer of self-organized nanosphere patterns. An ultra-thin Ag film coated at 5° tilt is shown to be an excellent substitute for a film deposited at 0° with double the thickness. There is a strong agreement between the experimental results and finite-elements-method-based Maxwell simulations exhibiting expected field enhancements up to 109 at a tilt angle of 5°.