ph2c00433_si_001.pdf (5.37 MB)
Optical Constants of Several Multilayer Transition Metal Dichalcogenides Measured by Spectroscopic Ellipsometry in the 300–1700 nm Range: High Index, Anisotropy, and Hyperbolicity
journal contributionposted on 2022-06-07, 19:09 authored by Battulga Munkhbat, Piotr Wróbel, Tomasz J. Antosiewicz, Timur O. Shegai
Transition metal dichalcogenides (TMDs) attract significant attention due to their remarkable optical and excitonic properties. It was understood already in the 1960s and recently rediscovered that many TMDs possess a high refractive index and optical anisotropy, which make them attractive for nanophotonic applications. However, accurate analysis and predictions of nanooptical phenomena require knowledge of dielectric constants along both in- and out-of-plane directions and over a broad spectral range, information that is often inaccessible or incomplete. Here, we present an experimental study of optical constants from several exfoliated TMD multilayers obtained using spectroscopic ellipsometry in the broad range of 300–1700 nm. The specific materials studied include semiconducting WS2, WSe2, MoS2, MoSe2, and MoTe2, as well as in-plane anisotropic ReS2 and WTe2 and metallic TaS2, TaSe2, and NbSe2. The extracted parameters demonstrate a high index (n up to ∼4.84 for MoTe2), significant anisotropy (n∥ – n⊥ ≈ 1.54 for MoTe2), and low absorption in the near-infrared region. Moreover, metallic TMDs show potential for combined plasmonic–dielectric behavior and hyperbolicity, as their plasma frequency occurs at around ∼1000–1300 nm depending on the material. The knowledge of optical constants of these materials opens new experimental and computational possibilities for further development of all-TMD nanophotonics.
plasma frequency occursextracted parameters demonstrateplane anisotropic resdielectric constants alonghigh refractive indexhigh index (<many tmds possessbroad spectral range2 subhigh indexbroad rangeplane directionsoptical constantsn ≈ 1∼ 4understood alreadytmd nanophotonicsspectroscopic ellipsometryremarkable opticalrecently rediscoveredoften inaccessiblenanophotonic applicationsmetallic taslow absorptioninfrared regionexperimental studyexcitonic propertiescomputational possibilitiesaccurate analysis