| Affiliation: | 1. Department of Electronics and Nanoengineering, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland;2. Faculty of Engineering and Natural Science, Photonics, Tampere University, 33720 Tampere, Finland;3. Department of Electronics and Nanoengineering, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland
QTF Center of Excellence, Department of Applied Physics, Aalto University, 00076 Aalto, Finland;4. Department of Applied Physics, Aalto University, 00076 Aalto, Finland |
| Abstract: | Developing selective and coherent polymorphic crystals at the nanoscale offers a novel strategy for designing integrated architectures for photonic and optoelectronic applications such as metasurfaces, optical gratings, photodetectors, and image sensors. Here, a direct optical writing approach is demonstrated to deterministically create polymorphic 2D materials by locally inducing metallic 1T′-MoTe2 on the semiconducting 2H-MoTe2 host layer. In the polymorphic-engineered MoTe2, 2H- and 1T′- crystalline phases exhibit strong optical contrast from near-infrared to telecom-band ranges (1–1.5 µm), due to the change in the band structure and increase in surface roughness. Sevenfold enhancement of third harmonic generation intensity is realized with conversion efficiency (susceptibility) of ≈1.7 × 10?7 (1.1 × 10?19 m2 V?2) and ≈1.7 × 10?8 (0.3 × 10?19 m2 V?2) for 1T′ and 2H-MoTe2, respectively at telecom-band ultrafast pump laser. Lastly, based on polymorphic engineering on MoTe2, a Schottky photodiode with a high photoresponsivity of 90 AW?1 is demonstrated. This study proposes facile polymorphic engineered structures that will greatly benefit realizing integrated photonics and optoelectronic circuits. |
