Deterministic Polymorphic Engineering of MoTe2 for Photonic and Optoelectronic Applications

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′-MoTe 2 on the semiconducting 2H-MoTe 2 host layer. In the polymorphic-engineered MoTe 2 , 2H- and 1T′- crystalline phases exhibit strong optical contrast from near-infrared to telecom-band ranges (1–1.5µm), 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 m 2 V −2 ) and ≈1.7×10 −8 (0.3×10 −19 m 2 V −2 ) for 1T′ and 2H-MoTe 2 , respectively at telecom-band ultrafast pump laser. Lastly, based on polymorphic engineering on MoTe 2 , a Schottky photodiode with a high photoresponsivity of 90 AW −1 is demonstrated. This study proposes facile polymorphic engineered structures that willgreatly benefit realizing integrated photonics and optoelectronic circuits.