Anisotropic Properties of Tellurium Nanoflakes Probed by Polarized Raman and Transient Absorption Microscopy: Implications for Polarization-Sensitive Applications

Abstract

Recently, the two-dimensional (2D) elemental material tellurium (Te) has drawn considerable attention, since it possesses high transport properties, wide broadband absorption, excellent thermoelectric properties, and prominent air stability. However, the anisotropic properties and carrier dynamics of this material are less stated. Here, Te nanoflakes are prepared by the hydrothermal method. Highly anisotropic properties are illustrated by polarized Raman spectra and transient absorption spectroscopic measurements as well as density functional theory (DFT) calculations. Photocarrier dynamincs are probed by temporally resolved transient measurements with an exciton lifetime of 25 ps. These results imply that Te can be treated as a competitive material for further anisotropic devices and applications.

Completely Anisotropic Ultrafast Optical Switching and Direction‐Dependent Photocarrier Diffusion in Layered ZrTe5

“…In addition to the completeness and robustness of the anisotropic modulation discussed so far, we emphasize that the scale of the peak DT amplitude (≈10 −2 ) is larger or similar to those of differential transmission/reflection values (≈10 −4 −10 −2 ) observed in other anisotropic 2D materials in the moderate pump fluence range (1—10 s µJ cm −2 ). [ 20,21,24,27–30,60,61 ] We also confirm that the near‐unity ρ persists at different pump fluences (Figure S7, Supporting Information), and the laser fluences we used do not degrade the sample. These outstanding properties suggest that ZrTe 5 is a potentially promising material for all‐optical ultrafast anisotropic applications, such as polarization‐controlled optical switches and modulators.…”

“…[18] Recently, the ultrafast control of the anisotropic optical properties of 2D materials has become a topic of interest, since it not only enables high-speed, polarizationcontrolled optical switches but also offers novel physical insights into anisotropic light-matter interactions and quantum coherences. [19][20][21][22][23][24][25][26][27][28][29] Moreover, their ultrafast spatiotemporal dynamics exhibit unique quasi-1D behavior of photocarriers with direction-dependent mobilities and diffusivities, offering essential information for improving the anisotropic devices. [30,31] However, despite the continuous emergence of novel anisotropic 2D materials, [6][7][8][9] ultrafast optical anisotropy has so far been explored for only a very limited class of materials.ZrTe 5 is a transition metal pentatelluride that has been extensively studied since the 1980s owing to its unique physical properties, such as resistivity anomaly (Figure S1, Supporting information), [32,33] large thermoelectric power, [34,35] and pressure-induced superconductivity.…”

Solution-processed thickness engineering of tellurene for field-effect transistors and polarized infrared photodetectors

“…36-1452), further confirming the trigonal structure of Te. The Raman spectrum in Figure 1E shows three sharp characteristic peaks at 91.5 cm −1 , 119.9 cm −1 , and 139.8 cm −1 , corresponding to the E 1 -TO, A 1 , and E 2 vibrational modes ( Pine and Dresselhaus, 1971 ; Tong et al, 2020 ; Wang et al, 2022 ). Lorentzian fitting of these peaks yields a narrow full width at half maximum of 3.6 cm −1 , 6.7 cm −1 , and 3.2 cm −1 , respectively ( Supplementary Figure S1 ).…”

Lattice dynamics in chiral tellurium by linear and circularly polarized Raman spectroscopy: crystal orientation and handedness

“…33,[37][38][39][40] More recently, studies exploring the strong in-plane anisotropy of Te by linearly polarized Raman measurements were able to determine the arrangement of the helical chains in solution-grown 2D Te flakes and confirm the results by electron microscopy imaging. 15,24,41 Furthermore, by combining circularly-polarized Raman spectroscopy and first-principle calculations, the handedness of Te bulk crystals could be tentatively determined. 34,35 However, to exploit Raman spectroscopy to identify the crystal orientation and handedness, a study of different crystallographic planes is necessary, while in the literature only one plane is reported.…”

“…34,35 However, to exploit Raman spectroscopy to identify the crystal orientation and handedness, a study of different crystallographic planes is necessary, while in the literature only one plane is reported. 15,24,41 In this work, we investigate trigonal Te by polarized Raman spectroscopy and the corresponding symmetry rules in bulk crystals. Unlike Te flakes, wires and nanocrystals, bulk Te gives access to several crystallographic planes.…”