Anomalous and Polarization-Sensitive Photoresponse of T<sub>d</sub> -WTe<sub>2</sub> from Visible to Infrared Light.
basic_science · Level V
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- Record sourced from PubMed, PMID 30516849.
- Also identified by DOI 10.1002/adma.201804629.
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Abstract
Recently, an emergent layered material T<sub>d</sub> -WTe<sub>2</sub> was explored for its novel electron-hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe<sub>2</sub> flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid- and far-infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light-induced surface bandgap opening from the first-principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W<sup>-1</sup> for a 3.8 µm laser at 77 K. Furthermore, the WTe<sub>2</sub> anomalous photocurrent matches its in-plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first-principles calculations confirm the angle-dependent bandgap opening of WTe<sub>2</sub> under polarized light irradiation. The anomalous and polarization-sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe<sub>2</sub> surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.