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Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires

Kaveh Baghbadorani, Masoud
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655

Abstract Details

2016, PhD, University of Cincinnati, Arts and Sciences: Physics.
In this dissertation, the dynamics of excitons in hybrid metal/organic/nanowire structures possessing nanometer thick deposited molecular and metal films on top of InP and GaAs nanowire (NW) surfaces were investigated. Optical characterizations were carried out as a function of the semiconductor NW material, design, NW size and the type and thickness of the organic material and metal used. Hybrid organic and plasmonic semiconductor nanowire heterostructures were fabricated using organic molecular beam deposition technique. I investigated the photon emission of excitons in ~150 nm diameter polytype wurtzite/zincblende InP NWs and the influence of a few ten nanometer thick organic and metal films on the emission using intensity- and temperature-dependent time-integrated and time resolved (TR) photoluminescence (PL). The plasmonic NWs were coated with an Aluminum quinoline (Alq3) interlayer and magnesium–silver (Mg0.9:Ag0.1) top layer. In addition, the nonlinear optical technique of heterodyne four-wave mixing was used (in collaboration with Prof. Wolfgang Langbein, University of Cardiff) to study incoherent and coherent carrier relaxation processes on bare nanowires on a 100 femtosecond time-scale. Alq3 covered NWs reveal a stronger emission and a longer decay time of exciton transitions indicating surface state passivation at the Alq3/NW interface. Alq3/Mg:Ag NWs reveal a strong quenching of the exciton emission which is predominantly attributed to Forster energy-transfer from excitons to plasmon oscillations in the metal cluster film. Changing the Mg:Ag to gold and the organic Alq3 spacer layer to PTCDA leads to a similar behavior, but the PL quenching is strongly increased. The observed behavior is attributed to a more continuous gold deposition leading to an increased Forster energy transfer and to a metal induced band-bending. I also investigated ensembles of bare and gold/Alq3 coated GaAs-AlGaAs-GaAs core shell NWs of 130 nm diameter. Plasmonic NWs with Au coating reveal a significant reduction of the PL intensity compared with the uncoated NWs. Organic-plasmonic NWs with an additional Alq3 interlayer show a noticeably stronger PL intensity which increases with rising Alq3 spacer thickness. Metal induced band bending is mainly attributed to be responsible for the PL quenching. TR PL measurements support our interpretation by showing an increase in the exciton decay times as we increase the spacer thickness. Au coated NWs also reveal a strong polarization dependent absorption which is mainly due to the significant dielectric mismatch between the nanowires and the adjacent vacuum environment. Finally, the amplified spontaneous emission (ASE) and possible plasmonic NW lasing from hybrid plasmonic core-shell GaAs NW heterostructures was investigated. The plasmonic heterostructures are composed of either bare NWs on an Au coated glass substrate or Au coated NWs on a bare glass substrate. Intensity-dependent PL on plasmonic NW samples reveals a super linear increase of the PL intensities which is attributed to an ASE at a threshold energy fluence of ~1 GW/cm2. Measurements above the threshold power reveal few weakly resolved broad bands around the maximum emission of the PL band which suggest plasmonic film induced lasing. This interpretation is supported by the fact that lasing from such ~100 nm narrow uncoated GaAs NWs is not possible.
Hans Peter Wagner, Ph.D. (Committee Chair)
Philip Argyres, Ph.D. (Committee Member)
Carlos Bolech, Ph.D. (Committee Member)
Howard Everett Jackson, Ph.D. (Committee Member)
191 p.
Physics
InP Nanowire; GaAs Nanowire; Optical Characterization; Organic Plasmonic Heterostructures; HFWM; Plasmonic Nanowire Lasing

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Citations

  • Kaveh Baghbadorani, M. (2016). Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655

    APA Style (7th edition)

  • Kaveh Baghbadorani, Masoud. Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655.

    MLA Style (8th edition)

  • Kaveh Baghbadorani, Masoud. "Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655

    Chicago Manual of Style (17th edition)

ucin1470754655
602
© 2016, some rights reserved.Creative Commons License Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires by Masoud Kaveh Baghbadorani is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.