In this study, near-infrared (NIR) x-polarized (P-state) light is created from the transmission ray of monoclinic multilayer GaTe near the band edge. The P-state transmittance photons are produced via the transmission light of a ribbonlike multilayer GaTe with a plurality of nanowire grids being parallel and constructed along the y direction (b axis) from 1.56 to 1.62 eV. At 300 K, a P-state excitonic emission at 1.652 eV can be clearly detected in polarized microphotoluminescence (μPL) measurement. The free-exciton extinction energy and recombination lifetime of the band-edge exciton are evaluated and determined to be ΔE = 32 ± 4 meV and τ ≈ 0.032 ns, respectively, for the multilayer GaTe. Polarized microthermoreflectance (μTR) measurement also verifies that the x-polarized transition is allowed while y-polarized (S-state) transition is forbidden in the multilayer GaTe. An asymmetric p-to-p transition along the x polarization is thus inferred to comprise the band edge of multilayer GaTe to form in-plane optical anisotropy.

In this work, structure, optical, and thermoelectric properties of layered ZrS2−xSex single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using I2 as the transport agent. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) results indicated that ZrS2−xSex (x = 0, 1, and 2) were crystalized in hexagonal CdI2 structure with one-layer trigonal (1T) stacking type. X-ray photoelectron and energy dispersive X-ray measurements revealed oxidation sensitive behavior of the chalcogenides series. Transmittance and optical absorption showed an indirect optical gap of about 1.78 eV, 1.32 eV, and 1.12 eV for the ZrS2−xSex with x = 0, 1, and 2, respectively. From the result of thermoelectric experiment, ZrSe2 owns the highest figure-of merit (ZT) of ~0.085 among the surface-oxidized ZrS2−xSex series layer crystals at 300 K. The ZT values of the ZrS2−xSex (x = 0, 1, and 2) series also reveal increase with the increase of Se content owing to the increase of carrier concentration and mobility in the highly Se-incorporated zirconium dichalcogenides with surface states.

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