Integration of thin-film hexagonal boron nitride with photonic microstructures

• Author / Creator

  Scheuer, Kyle G.

• Single photon emitters hosted in hexagonal boron nitride have attracted significant attention over the past 5 years. This is in part due to their room temperature operation, chemical and physical stability, and high quantum efficiency. Continuous hexagonal boron nitride thin films (~ 10 – 20 nm thick) are of particular interest because of their potential to be integrated with existing silicon photonics devices. Additionally, there have been multiple reports of the deterministic activation of hBN emitters through the introduction of strain on the materials crystal lattice.
  This thesis describes the theory, fabrication, and characterization of hexagonal boron nitride coated nano-/micro-structures as a method of both deterministically activating defect centers as well as spatially aligning them to resonant antinodes in buckled microcavity devices. First, the design and construction of an epifluorescence spectroscope/microscope instrument crucial to the optical characterization of hBN emitters, is presented. A particular emphasis was placed on accounting for undesirable autofluorescence from microscope objectives.
  Next, a thin-film transfer technique for hexagonal boron nitride (hBN) multilayers was developed and refined. The technique was then used to transfer continuous hBN films to SiO2 substrates patterned with structures ~ 100 – 200 nm in height with lateral dimensions on the order of a few μm. Blanketing the film over nanoscale-height features introduces strain on the hBN crystal lattice near feature edges, causing naturally present defects to emit across much of the visible range. Notably, the brightness of emitting arrays was characterized and shown to be much greater than emission from unintentional wrinkles in the film.
  The transfer process was then used as a means of integrating hBN emitters inside recently demonstrated buckled microcavities, where two Bragg mirrors separated by a low-adhesion layer are thermally shocked resulting in the formation of a closed cavity structure due to the stress inherent to the thin films comprising the top mirror. Both the active and passive optical properties of the resulting devices were then measured. The scalability and deterministic placement provided by the hBN transfer process paired with the potential for cavity enhancement offers a promising platform for a real-world single photon source with broad applications in quantum information and computing.

• Subjects / Keywords

  • hexagonal boron nitride
  • thin film optics
  • microfabrication
  • optics
  • 2D materials

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-9s2q-d074

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.