Epitaxial growth and plasmonic coupling in topological insulator heterostructures
| Author(s) | Wang, Zhengtianye | |
| Date Accessioned | 2022-10-20T12:30:11Z | |
| Date Available | 2022-10-20T12:30:11Z | |
| Publication Date | 2022 | |
| SWORD Update | 2022-08-10T19:08:58Z | |
| Abstract | Three-dimensional (3D) topological insulator (TI) belongs to the group of quantum spin Hall insulators that exhibit helical superconducting surface states and insulating bulk states. Electrons occupying these surface states are two-dimensional (2D) massless, linear dispersed, and spin-momentum locked Dirac Fermions. The optical transitions among these surface states, for example Dirac plasmon polariton, are in the far-IR THz spectral range, which is hardly accessed by traditional semiconductors. These unique properties enable TI a promising platform for far-IR sensing, security screening, and other optoelectronic devices that function in the THz. ☐ The epitaxial growth of chalcogenide TI family Bi2Se3, Bi2Te3, and Sb2Te3 is dominated by van der Waals epitaxy. To produce high quality thin film for optical application, the growth of TI must be optimized to fit the needs on various substrates. The first part of this dissertation discusses the general growth strategies that are applicable for molecular beam epitaxy of van der Waals materials. The material demonstrates very different growth dynamics on substrates with inert surface and on substrates with reactive surface. The growth strategy must be carefully chosen to enable the van der Waals epitaxy. With mature growth methods of TI, we are able to create functional TI heterostructures like superlattice. In single TI thin film, Dirac plasmons are excited simultaneously on the top and bottom surfaces. They are electrostatically coupled and generate an optical mode and an acoustic mode. It is not clear if the multiple surface states introduced by stacking alternating TI and band insulator (BI) layers will also couple and produce additional plasmon modes, which may possess extraordinarily high wavevectors useful for waveguiding and sub-diffraction limit imaging. The second part of the dissertation deals with optical modeling and experimental confirmation of such multiple surface states coupling. It is shown that two Bi2Se3 TI layer separated by BI layer can be electrostatically coupled and generate plasmon mode at higher frequency than the single layer Bi2Se3 at same wavevector, and that the coupling strength is a function of the TI layer spacing. Adding more TI layers in the superlattice structure gives birth to hyperbolic volume plasmon polariton modes at higher frequency but the higher order modes generated are hard to be observed due to high damping and limited substrate transmission window. This dissertation clarifies the challenges and directions for realizing hyperbolic metamaterials based on topological insulators. | en_US |
| Advisor | Law, Stephanie | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Materials Science and Engineering | |
| DOI | https://doi.org/10.58088/p29w-tb17 | |
| Unique Identifier | 1348289037 | |
| URL | https://udspace.udel.edu/handle/19716/31512 | |
| Language | en | |
| Publisher | University of Delaware | en_US |
| URI | https://login.udel.idm.oclc.org/login?url=https://www.proquest.com/dissertations-theses/epitaxial-growth-plasmonic-coupling-topological/docview/2700764937/se-2?accountid=10457 | |
| Keywords | Plasmonic coupling | en_US |
| Keywords | Insulator heterostructures | en_US |
| Keywords | Epitaxial growth | en_US |
| Title | Epitaxial growth and plasmonic coupling in topological insulator heterostructures | en_US |
| Type | Thesis | en_US |