Abstract
Hyperbolic phonon polaritons (HPhPs) in hexagonal boron nitride (hBN) enable the direct manipulation of mid-infrared light at nanometer scales, many orders of magnitude below the free-space light wavelength. High-resolution monochromated electron energy-loss spectroscopy (EELS) facilitates measurement of excitations with energies extending into the mid-infrared while maintaining nanoscale spatial resolution, making it ideal for detecting HPhPs. The electron beam is a precise source and probe of HPhPs, which allows the observation of nanoscale confinement in HPhP structures and directly extract hBN polariton dispersions for both modes in the bulk of the flake and modes along the edge. The measurements reveal technologically important nontrivial phenomena, such as localized polaritons induced by environmental heterogeneity, enhanced and suppressed excitation due to 2D interference, and strong modification of high-momenta excitations such as edge-confined polaritons by nanoscale heterogeneity on edge boundaries. The work opens exciting prospects for the design of real-world optical mid-infrared devices based on hyperbolic polaritons.
| Original language | English |
|---|---|
| Article number | 2103404 |
| Journal | Small |
| Volume | 17 |
| Issue number | 39 |
| DOIs | |
| State | Published - Oct 1 2021 |
Funding
Microscopy experiments were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility using instrumentation within ORNL's Materials Characterization Core provided by UT‐Battelle, LLC, under Contract No. DE‐AC05‐ 00OR22725 with the DOE and sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT‐Battelle, LLC, for the U.S. Department of Energy (JAH). A.K. and F.J.G.d.A. acknowledge support from the European Research Council (Advanced Grant No. 789104eNANO), the European Commission (Horizon 2020 Grants No. FET‐Proactive 101017720‐EBEAM and No. FET‐Open 964591‐SMART‐electron), and the Spanish MINECO (SEV2015‐0522). Support for hBN crystal growth from the Office of Naval Research (Award No. N00014‐20‐1‐2474) is appreciated (J.L. and J.H.E.). Microscopy experiments were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility using instrumentation within ORNL's Materials Characterization Core provided by UT-Battelle, LLC, under Contract No. DE-AC05- 00OR22725 with the DOE and sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy (JAH). A.K. and F.J.G.d.A. acknowledge support from the European Research Council (Advanced Grant No. 789104eNANO), the European Commission (Horizon 2020 Grants No. FET-Proactive 101017720-EBEAM and No. FET-Open 964591-SMART-electron), and the Spanish MINECO (SEV2015-0522). Support for hBN crystal growth from the Office of Naval Research (Award No. N00014-20-1-2474) is appreciated (J.L. and J.H.E.).
| Funders | Funder number |
|---|---|
| Office of Naval Research | N00014-20-1-2474 |
| U.S. Department of Energy | |
| Office of Science | DE‐AC05‐ 00OR22725 |
| Oak Ridge National Laboratory | |
| Horizon 2020 Framework Programme | 964591, 101017720, 789104 |
| European Commission | |
| European Research Council | |
| Ministerio de Economía y Competitividad | SEV2015‐0522 |
| Horizon 2020 |
Keywords
- 2D materials
- hexagonal boron nitride
- hyperbolic phonon polaritons
- infrared spectroscopy
- monochromated electron energy-loss spectroscopy
- nanophotonics
- optoelectronics