Subcategory: Electrical Engineering
Room: Park Tower 8216
Vivian Zhou - Case Western Reserve University
Hexagonal boron nitride (h-BN), a paradigm of two-dimensional (2D) materials, possesses ultrawide electronic bandgap (5.9 eV) and excellent chemical and thermal stability. With the ultimate thinness, h-BN has primarily been employed as lattice-matched high-κ dielectric layers in 2D electronics. The outstanding mechanical properties of h-BN (a Young’s modulus theoretically predicted to be as high as ~780 GPa and a very high breaking strain limit of ~22%) also enable 2D nanoelectromechanical systems. Recently, h-BN has emerged as a promising platform for nanophotonics as well, hosting hyperbolic phonon-polaritons and robust quantum emitters at room temperature. However, a small refractive index of h-BN (~1.8) impedes the exploitation in the photonic domain, which makes it hard to achieve a high refractive index contrast that is required for efficient light confinement in the visible spectral range. Therefore, in this study, we employ optical micro-spectroscopic methods to characterize the light-matter interaction in h-BN layers. Combining with numerical simulation, we have systematically evaluated the influence of crystal thickness, dielectric environment, excitation wavelength on the light outcoupling efficiency. We demonstrate that the light engages in multiple reflections with h-BN layers and underlying substrates, forming interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Moreover, we propose a novel approach to improve the light coupling in h-BN by engineering the dielectric surroundings. The present work will provide valuable guidelines to design and optimize the photonic devices based on h-BN towards integrated photonic systems. References: Kubota Y, Watanabe K, Tsuda O et al. Deep ultraviolet light-emitting hexagonal boron nitride synthesized at atmospheric pressure. Science 2007; 317: 932–934. Dean CR, Young AF, Meric I et al. Boron nitride substrates for high-quality graphene electronics. Nature Nanotechnology 2010; 5: 722–726. Wu J, Wang B, Wei Y et al. Mechanics and mechanically tunable band gap in single-layer hexagonal boron-nitride. Materials Research Letters 2013; 1: 200–206. Song L, Ci L, Lu H et al. Large scale growth and characterization of atomic hexagonal boron nitride layers. Nano Letters 2010; 10: 3209–3215. Ambrosio A, Jauregui LA, Dai S et al. Magnetic Detection and Imaging of Hyperbolic Phonon Polaritons in Hexogonal Boron Nitride. ASC Nano 2017; 11: 741-8746. Exarhos AL, Hopper DA, Grote RR et al. Otpical Signatures of Quantum Emitters in Suspended Hexogonal Boron Nitride. ACS Nano 2017; 11:3328-3336. Kim S, Froch JE, Christian J et al. Photonic Crystal Cavities from Hexogonal Boron Nitride. Nature Communciations 2018; 9:2623.
Funder Acknowledgement(s): Funder Acknowledgement: Funding was provided by an NSF EFRI. Faculty Advisor/Mentor: Philip Feng, firstname.lastname@example.org
Faculty Advisor: Philip Feng, email@example.com
Role: I was involved in a large part of the research. My mentor originally proposed the idea and concept to kick start my project in this area. I have done extensive literature review to familiarize myself with the cutting edge research that has been done in this area and also to adapt methods for my own data gathering. I took part in the spectroscopic measurements indicated in the abstract and received help and training from a post doc in my group for usage of the lab equipment. I also performed the numerical simulations to characterize light matter interaction and solve for optimal parameters for coupling.