Bulletin of the American Physical Society
75th Annual Meeting of the Southeastern Section of APS
Volume 53, Number 13
Thursday–Saturday, October 30–November 1 2008; Raleigh, North Carolina
Session GB: Forefront Materials Physics II |
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Chair: Matthew Edwards, Alabama A&M University Room: Holiday Inn Brownstone Roosevelt |
Friday, October 31, 2008 8:30AM - 9:00AM |
GB.00001: Plasmon Polariton Excitation and Enhancement of the Magneto-optical Activity Invited Speaker: Light can be localized and manipulated in metallic and metallo- dielectric nanoparticle arrays and/or thin film structures via Plasmon Polariton excitation. This phenomenon is very sensitive to slight changes in the dielectric constant at the surface and it has been successfully applied to bio-sensing. [1] During the Plasmon excitation the associated electric field is strongly enhanced near the dielectric-metal interface, [2] and this can also enhance magneto-optical activity in magnetic layers and/or nanomagnets. We have studied this effect in Au/Co/Au tri-layered structures, and we measured the reflectivity (R) under an alternating magnetic field and found that the surface Plasmon excitation itself depends on the applied magnetic field because of the magnetic field dependence of its wave vector. We have achieved remarkably high $\Delta $R/R modulated performance, in excess of 150{\%} at moderate magnetic fields externally applied, when excited in Kretschmann configuration [3]. \\[3pt] [1]. Jung, L.S. et al, \textit{Sensors and Actuators} $B$ \textbf{54}, 137-144 (1999); Lu, H.B., et al., \textit{Sensors and Actuators B-Chemical} \textbf{74}(1-3), 91-99 (2001); Jung, L. S. et al, \textit{Langmuir} \textbf{14}, 5636-5648 (1998). \\[0pt] [2]. C. Hermann, \textit{Phys. Rev. B} \textbf{63}, 235422 (2001 \\[0pt] [3]. E. Kretschmann, \textit{Z.Phys.} \textbf{241,} 313, (1971). [Preview Abstract] |
Friday, October 31, 2008 9:00AM - 9:30AM |
GB.00002: Electrophoretic Deposition of Thin Films of Nanoparticles Invited Speaker: Nanoparticles have attracted considerable interest recently due to their size-dependent, quantum confinement characteristics, which make them attractive for an array of optical, magnetic, and electronic devices. For nanoparticles to be employed in an array of commercial and industrial applications, a technique for the facile, site-selective assembly of homogeneous, densely packed, defect-free thin films must be realized. Widely used methods for casting nanoparticle (NP) constituents into films have recognized limitations, including the inability to achieve both large-scale ordering of the nanoparticles and robust chemical and structural properties. NP deposition schemes also require an understanding of both the NP dynamics in suspension and the interactions that govern nanoparticle-substrate and nanoparticle-nanoparticle binding. Although research has been conducted on the assembly of nanoparticles with a distribution of surface charge states, little has been done on the assembly of like-charged nanoparticles. The only NP deposition scheme that considers the physical characteristics of the NPs in the film formation and incorporates the most favorable attributes of NP deposition is electrophoretic deposition (EPD). Recent progress in the NP EPD will be the emphasis of this presentation. Highlighted are the recent discoveries of the size dependence of the thickness of iron oxide NP films and the fabrication of free-standing NP films. [Preview Abstract] |
Friday, October 31, 2008 9:30AM - 10:00AM |
GB.00003: Photonic Structuring of Bulk Heterojunction Organic Solar Cells Invited Speaker: The major challenge in solar cell technology dwells in achieving an efficient absorption of photons with an effective carrier extraction. In all cases, light absorption considerations call for thicker modules while carrier transport would benefit from thinner ones. This dichotomy is the fundamental problem limiting the efficiencies of photovoltaics, especially promising low-cost polymer solar cells. We present experimental and theoretical solutions to this problem applying photonic crystal nanostructuring in bulk heterojunction solar cells made of poly-3-hexylthiophene:[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). We discuss theoretical models of optical absorption that occur for the photonic design that result in a 22{\%} enhancement over a conventional planar cell. We also calculate the local exciton creation profile within the photonic crystal structure to show nanopatterning also reduces carrier transport length. Finally, experimental results are presented that follow the theoretical predictions along with our nano fabrication method to show this approach can be used to produce improved large-area nanostructured P3HT:PCBM solar cells. In collaboration with John Tumbleston, Physics and Astronomy Department, University of North Carolina at Chapel Hill; and Doo-Hyun Ko and Edward Samulski, Chemistry Department, University of North Carolina at Chapel Hill. [Preview Abstract] |
Friday, October 31, 2008 10:00AM - 10:30AM |
GB.00004: Bulk crystal growth of scintillator materials for gamma ray detectors Invited Speaker: Within the past few years, it has been demonstrated that several new rare earth halide scintillation detector crystals such as cerium doped lanthanum bromide (LaBr$_{3}$:Ce) have high output and improved energy deposit to light linearity and thus they can substantially enhance the performance of the next generation of gamma ray detectors. These detectors have a variety of applications in NASA hard x-ray and gamma ray missions, high energy physics, home land security and medical imaging applications. This cerium doped lanthanum bromide crystal has $\sim $1100{\%} the light output of BGO, resulting in better energy resolution than conventional scintillators. This is equivalent to 60000 photons per MeV of deposited energy. This new series of scintillator materials promise to usher a breakthrough in the field, if sufficiently large and clear crystals of this material can be grown. These halides however are highly hygroscopic and hence pose some difficulty in growing crystals. Efforts are being made to grow this and other materials in this family of crystals and successful results have been achieved. An overview of the challenges encountered during the synthesis and melt crystal growth of these rare earth halide scintillators shall be presented. [Preview Abstract] |
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