Browsing by Subject "Infrared spectroscopy"
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Item Atomic layer lithography of plasmonic nanogaps for enhanced light-matter interactions: fabrication and applications(2016-01) Chen, XiaoshuEnhanced light-matter interactions at the nanometer scale have many potential applications, such as thin film sensing, enhanced Raman scattering, enhanced infrared absorption, particle manipulation, among others. Metal – insulator – metal nanogap structure is one of the most effective plasmonic devices for such applications since they are capable of generating the strongest light field enhancement inside the nanogap. However, current techniques to make such nanogap structures are either very expensive, slow, or lacking of control over nanogap size, pattern shape, and position. In this thesis, two wafer-scale fabrication methods are presented to address the challenges in fabrication. The fabricated devices are then used to demonstrate the above-mentioned applications. Atomic layer deposition is used in both methods to define the width of nanogap with angstrom resolution. The length, position, and shape of the nanogaps are precisely controlled in wafer scale by photolithography and metal deposition. A simple tape peeling and a template stripping process are used to expose the nanogaps. Nanogap devices with different designs are proved to support strong optical resonances in visible, near infrared, mid infrared, and terahertz-frequency regimes. By squeezing electromagnetic waves into nanometer wide gaps, huge field enhancement can be achieved inside the gaps. These novel fabrication methods can easily be duplicated and thus lead to broad studies and applications of the enhanced light-matter interactions.Item Evaluation of Bio-Fog Sealants for Pavement Preservation(Center for Transportation Studies, University of Minnesota, 2016-06) Ghosh, Debaroti; Turos, Mugur; Marasteanu, MihaiPavement preservation is playing an increasingly significant role in maintaining our aging pavement infrastructure. One important component is the application of sealants to the pavement surface. In a joint study between MnDOT and the University of Minnesota, the field performance and mechanical properties of asphalt mixtures from pavement sections treated with a number of new products, called bio sealants, is investigated. The objective of the study is to obtain relevant properties of treated asphalt materials to understand the mechanism by which sealants improve pavement performance. Laboratory testing was performed on treated asphalt binder and mixtures. For binders, a dynamic shear rheometer and a bending beam rheometer were used to obtain rheological properties of treated and untreated asphalt binders. Field cores from both untreated and treated sections were collected and thin beam specimens were prepared from the cores to compare the creep and strength properties of field-treated and laboratory-treated asphalt mixture. It is observed that the oil-based sealants have a significant softening effect on the control binder compared to the water-based sealants. For asphalt mixtures, different trends are observed for the field samples compared to the laboratory prepared samples. Similar to binder results, significant differences are observed between the asphalt mixtures treated with oil-based and water-based sealants, respectively. From the analysis performed on the bending creep and strength results at low temperature, it is concluded that the application of sealants in the field have no significant effect on these properties. Fourier transform infrared spectroscopy (FTIR) analysis showed that the sealant products could not be detected in mixture samples collected from the surface of the treated section.