Temperature-Dependent Raman Responses of the Vapor-Deposited Tin Selenide Ultrathin Flakes

Abstract

Tin selenide (SnSe) is a newly emerging layered material. SnSe with low dimensionality has been reported as an appealing material with a diverse range of applications such as rechargeable lithium-ion batteries, memory switching devices, solar energy conversion, thermoelectric energy conversion, and near-infrared optoelectronic devices. Here we synthesized SnSe ultrathin flakes on SiO2/Si substrates through simple vapor deposition route and investigated its temperature-dependent Raman spectroscopy behavior with 532, 633, and 785 nm excitation wavelengths. It was found that the Ag 2, Ag 3, and B3g modes soften as temperature increases from 98 to 298 K under all wavelengths. Our results revealed anharmonic phonon properties of SnSe, and they will benefit the advanced study of its thermal properties. This approach will also have large application in characterizing the optical, electronic, and thermal properties of other novel layered materials. Moreover, our results can be utilized to measure the temperature of SnSe-based nanodevices without destruction.

Weak Interlayer Interaction in 2D Anisotropic GeSe2

“…The extracted χ for mode Ag at 210 cm −1 is −0.0095 cm −1 K −1 . The obtained value for GeSe 2 is much smaller than that for other 2D layered materials such as BP (−0.023 cm −1 K −1 for A 2 g mode), SnS (−0.036 cm −1 K −1 for A 2 g mode), and SnSe (−0.0377 cm −1 K −1 for A 2 g mode), while nearly equal to ReSe 2 (−0.0074 cm −1 K −1 for A g ‐like mode) and in good agreement with the previous report . It was reported that the first‐order temperature coefficients of the Raman active modes were associated with the interlayer interaction between the layers of 2D layered materials .…”

“…In addition to the room temperature Raman spectroscopy, we also performed the temperature‐dependent Raman spectroscopy, which can provide exact information on thermal expansion, thermal conductivity, and interlayer coupling . In view of convenience, we selected the most intensive Ag mode located at 210 cm −1 for further detailed analysis.…”

Ultrathin 2D GeSe2 Rhombic Flakes with High Anisotropy Realized by Van der Waals Epitaxy

“…Two peaks located at 32.3 and 55.1 eV can be assigned to the Ge 3d and Se 3d core-level peaks, respectively. [36] The variation of Raman frequency can be determined by: [37] [17] We then obtained the temperature-dependent Raman spectroscopy for the GeSe 2 rhombic flakes (Figure 3); such a study is an efficient way to investigate the thermal expansion, thermal conductivity, and interlayer coupling.…”

“…The calculated χ coefficient is −0.00546 cm −1 K −1 for the peak at 210 cm −1 , which is several times smaller than those of other 2D layered materials such as SnSe 2 (A 1g mode, χ = −0.0129 cm −1 K −1 ), [35] MoS 2 (E 1 2g mode, χ = −0.0136 cm −1 K −1 ), [38] and SnSe (B 3g mode, χ = −0.03318 cm −1 K −1 ). For SnS, [19] SnSe, [36] the higher temperature coefficients may arise from the strong van der Waals interaction between the adjacent layers caused by their unique puckered crystal structures. For SnS, [19] SnSe, [36] the higher temperature coefficients may arise from the strong van der Waals interaction between the adjacent layers caused by their unique puckered crystal structures.…”

“…For SnS, [19] SnSe, [36] the higher temperature coefficients may arise from the strong van der Waals interaction between the adjacent layers caused by their unique puckered crystal structures. [36,38] Angle-resolved polarized Raman spectroscopy was obtained at room temperature. Figure 3c shows how the full-width at half-maximum (FWHM) of the A g mode at 210 cm −1 is significantly affected by the temperature; it increases from 8.5 to 10 cm −1 when the temperature increases from 80 to 300 K. Accordingly, it is deduced that the temperature-dependent line width could be attributed to the zone center optical phonon decaying into an optical phonon and an acoustic phonon.…”