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Exploring the Photoresponse and Optical Selection Rules in the Semiconductor Nanowires, Topological Quantum Materials and Ferromagnetic Semiconductor Nanoflakes using Polarized Photocurrent Spectroscopy

Pournia, Seyyedesadaf
http://orcid.org/0000-0002-5026-4720
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666632280473

Abstract Details

2021, PhD, University of Cincinnati, Arts and Sciences: Physics.
Studying the interaction between light and materials is a novel approach for characterizing the optical and electrical properties of solids. In addition to increasing our understanding of the physics of different material systems, optical spectroscopy has numerous applications in the field of energy, sensing, lasers, and quantum information processing. In this dissertation, we have utilized polarized photocurrent spectroscopy to investigate the electronic energy band structure and optical selection rules which control the optical transitions between the energy states, in a variety of photosensitive nanomaterial systems. The nanomaterials studied in this dissertation are the semiconductor wurtzite (WZ) InAs nanowires, topological insulator (TI) Bi2Se3 nanoflakes, Weyl semimetal (WSM) NbIrTe4 nanoflakes and ferromagnetic semiconductor CrSiTe3 nanoflakes. To measure the photocurrent signal of these materials, metal electrodes were fabricated at the two ends of nanostructures by using photolithographic methods. We will see that the photoresponse could be generated through different processes in these material systems, such as photoconductivity, photothermoelectric and nonlinear effects such as photogalvanic. In the first part of this dissertation, linearly polarized light is used to investigate the band structure of hexagonal Wurtzite InAs in a nanowire device. Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory. The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate. From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs. This information is vital to the development of crystal phase engineering of this important III-V semiconductor. In the second part, we explore optical excitations by using the photothermoelectric effect in a topological insulator Bi2Se3 nanoflake device. We show this photothermoelectric generated photoresponse is proportional to the absorption coefficient of the material. In addition, other optical interactions cause a linear-polarization dependent photoresponse in the device. In the third part, we explore the photoresponse of a device fabricated from a NbIrTe4 Weyl semimetal nanoflake to linearly and circularly polarized light in the mid-infrared. At high energies (1.8 eV) the photothermoelectric effect dominates the photoresponse with very little polarization dependence. At lower energies (~ 0.3 eV), the photothermoelectric effect decreases substantially, while the circular photogalvanic effect dominates. The energy-dependent circular photogalvanic effect also shows a peak at higher energies suggesting a potential interband transition from the linearly dispersed energy states hosting the Weyl carriers to the heavier conduction energy states. In the last section, we explore the external bias induced nonlinear effect in a ferromagnetic semiconductor CrSiTe3 device. Although this second order optical photoresponse is prohibited by the symmetry of the material, we show that the external bias induces a linear polarization dependent photocurrent generated by this nonlinear effect in this device which is stronger at temperatures less than the Currie temperature (33 K) of this ferromagnetic material.
Leigh Smith, Ph.D. (Committee Chair)
Howard Jackson, Ph.D. (Committee Member)
Kay Kinoshita, Ph.D. (Committee Member)
Yashar Komijani, Ph.D. (Committee Member)
Hans-Peter Wagner, Ph.D. (Committee Member)
134 p.
Condensation
Photocurrent spectroscopy in nanomaterial devices; Wurtzite III-V semiconductor nanowires; Type II Weyl semimetals NbIrTe4; Photogalvanic effect; Ferromagnetic semiconductor CrSiTe3; Topological insulator Bi2Se3

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Citations

  • Pournia, S. (2021). Exploring the Photoresponse and Optical Selection Rules in the Semiconductor Nanowires, Topological Quantum Materials and Ferromagnetic Semiconductor Nanoflakes using Polarized Photocurrent Spectroscopy [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666632280473

    APA Style (7th edition)

  • Pournia, Seyyedesadaf. Exploring the Photoresponse and Optical Selection Rules in the Semiconductor Nanowires, Topological Quantum Materials and Ferromagnetic Semiconductor Nanoflakes using Polarized Photocurrent Spectroscopy. 2021. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666632280473.

    MLA Style (8th edition)

  • Pournia, Seyyedesadaf. "Exploring the Photoresponse and Optical Selection Rules in the Semiconductor Nanowires, Topological Quantum Materials and Ferromagnetic Semiconductor Nanoflakes using Polarized Photocurrent Spectroscopy." Doctoral dissertation, University of Cincinnati, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666632280473

    Chicago Manual of Style (17th edition)

ucin1627666632280473
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This open access ETD is published by University of Cincinnati and OhioLINK.