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  1. Abstract

    Exploiting polaritons in natural vdW materials has been successful in achieving extreme light confinement and low-loss optical devices and enabling simplified device integration. Recently, α-MoO3has been reported as a semiconducting biaxial vdW material capable of sustaining naturally orthogonal in-plane phonon polariton modes in IR. In this study, we investigate the polarization-dependent optical characteristics of cavities formed using α-MoO3to extend the degrees of freedom in the design of IR photonic components exploiting the in-plane anisotropy of this material. Polarization-dependent absorption over 80% in a multilayer Fabry-Perot structure with α-MoO3is reported without the need for nanoscale fabrication on the α-MoO3. We observe coupling between the α-MoO3optical phonons and the Fabry-Perot cavity resonances. Using cross-polarized reflectance spectroscopy we show that the strong birefringence results in 15% of the total power converted into the orthogonal polarization with respect to incident wave. These findings can open new avenues in the quest for polarization filters and low-loss, integrated planar IR photonics and in dictating polarization control.

  2. Free, publicly-accessible full text available June 22, 2023
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  5. Abstract Chemical vapor deposition growth of metal carbides is of great interest as this method provides large area growth of MXenes. This growth is mainly done using a melted diffusion based process; however, different morphologies in growth process is not well understood. In this work, we report deterministic synthesis of layered (non-uniform c -axis growth) and planar (uniform c -axis growth) of molybdenum carbide (Mo 2 C) using a diffusion-mediated growth. Mo-diffusion limited growth mechanism is proposed where the competition between Mo and C adatoms determines the morphology of grown crystals. Difference in thickness of catalyst at the edge and center lead to enhanced Mo diffusion which plays a vital role in determining the structure of Mo 2 C. The layered structures exhibit an expansion in the lattice confirmed by the presence of strain. Density functional theory shows consistent presence of strain which is dependent upon Mo diffusion during growth. This work demonstrates the importance of precise control of diffusion through the catalyst in determining the structure of Mo 2 C and contributes to broader understanding of metal diffusion in growth of MXenes.
    Free, publicly-accessible full text available January 1, 2023