Browsing by Author "Burton, John"

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    Optical properties of Pb0.52Zr0.48TiO3 nanorod arrays: second harmonic generation and multiphoton carrier dynamics
    Mudiyanselage, Rathsara R. H. H.; Burton, John; Magill, Brenden A.; McMillan, Kiara; Gagliano, Gabriella; Morral, Ada J.; Kang, Min Gyu; Kang, Han Byul; Priya, Shashank; Stanton, Christopher J.; Khodaparast, Giti A. (2021-07)
    Nonlinear optical properties of poled and unpoled, lead zirconate-titanate (Pb0.52Zr0.48TiO3) nanorod arrays, grown on Pt-coated Si with similar to 200 nm diameter and similar to 600 nm height, were investigated. Clear signatures of second harmonic generations (SHG), from 490-525 nm (2.38-2.53 eV) at room temperature, were observed. Furthermore, time resolved differential reflectivity measurements were performed to study dynamical properties of photoexcited carriers in the range of 690-1000 nm where multiphoton processes were responsible for the photo-excitations. We compared this excitation scheme, which is sensitive mainly to the surface states, to when the photoexcited energy (similar to 3.1 eV) was close to the band gap of the nanorods. Our results offer promises for employing these nanostructures in nonlinear photonic applications.
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    Self-assembled PCBM bilayers on graphene and HOPG examined by AFM and STM
    Li, Yanlong; Chen, Chuanhui; Burton, John; Park, Kyungwha; Heflin, James R.; Tao, Chenggang (2018-05-04)
    In this work we report fabrication and characterization of phenyl-C61-butyric acid methyl ester (PCBM) bilayer structures on graphene and highly oriented pyrolytic graphite (HOPG). Through careful control of the PCBM solution concentration (from 0.1 to 2 mg ml(-1)) and the deposition conditions, we demonstrate that PCBM molecules self-assemble into bilayer structures on graphene and HOPG substrates. Interestingly, the PCBM bilayers are formed with two distinct heights on HOPG, but only one unique representative height on graphene. At elevated annealing temperatures, edge diffusion allows neighboring vacancies to merge into a more ordered structure. This is, to the best of our knowledge, the first experimental realization of PCBM bilayer structures on graphene. This work could provide valuable insight into fabrication of new hybrid, ordered structures for applications to organic solar cells.