Temperature Dependent Excitonic Transition Energy and Enhanced Electron-Phonon Coupling in Layered Ternary SnS2-xSex Semiconductors with Fully Tunable Stoichiometry

Abstract

In this study, a series of SnS2-xSex (0 ≤ x ≤ 2) layered semiconductors were grown by the chemical–vapor transport method. The crystal structural and material phase of SnS2-xSex layered van der Waals crystals was characterized by X-ray diffraction measurements and Raman spectroscopy. The temperature dependence of the spectral features in the vicinity of the direct band edge excitonic transitions of the layered SnS2-xSex compounds was measured in the temperature range of 20–300 K using the piezoreflectance (PzR) technique. The near band-edge excitonic transition energies of SnS2-xSex were determined from a detailed line-shape fit of the PzR spectra. The PzR characterization has shown that the excitonic transitions were continuously tunable with the ratio of S and Se. The parameters that describe the temperature variation of the energies of the excitonic transitions are evaluated and discussed.

Direct Synthesis of Two-Dimensional SnSe and SnSe2 through Molecular Scale Preorganization

“…EDX mapping (Figure a) showed an equal distribution of tin and selenium, and also in the case of the ternary particles, sulfur is found within the particles. The powder X-ray diffraction data (Figure b) corresponded to SnSe 2 ( P 3̅ m 1), although a slight shift toward larger diffraction angles can be observed for SnS 0.13 Se 1.79 (Figure c), which is probably due to the incorporation of a smaller sulfide anion, which is in accord with other reports. , …”

“…In pure SnS 2 , the Sn–S A 1g mode can be observed at 317 cm –1 . Yu et al and Lin et al showed that in SnS x Se 2– x alloys the Sn–S A 1g mode is shifted toward lower wavenumbers with a decrease in intensity, if the selenium content is increased. , The Sn–S E g mode expected , below 202 cm –1 could not be observed due to its low intensity, when compared to the Sn–S A 1g mode in general and its overlapping position with the Sn–Se A 1g mode.…”

“…The powder X-ray diffraction data (Figure 10b) corresponded to SnSe 2 (P3̅ m1), although a slight shift toward larger diffraction angles can be observed for SnS 0.13 Se 1.79 (Figure 10c), which is probably due to the incorporation of a smaller sulfide anion, which is in accord with other reports. 69,70 The typical Sn−Se A 1g and E g modes related to SnSe 2 and SnS 0.13 Se 1.79 particles were present in the Raman spectra at 183 and 115/116 cm −1 , respectively (Figure 10d). 71 Additionally, the A g mode corresponding to SnSe could be identified in both samples at 67/69 cm −1 .…”

Broadband Optical Constants and Nonlinear Properties of SnS2 and SnSe2

“…According to the Joint Committee on Powder Diffraction Standards (card No. 23-0677 and 89-2939) and previous publications [ 27 , 47 , 48 ], the obtained XRD patterns reveal the hexagonal lattice configuration, which could be 1T or 2H, for SnS 2 and SnSe 2 with lattice parameters a = b = 3.6486 Å and c = 5.8992 Å for SnS 2 and a = b = 3.811 Å and c = 6.137 Å for SnSe 2 .…”