Synthesis, characterization and chemical stability of silicon dichalcogenides, Si(Se S1−)2

Abstract

Silicon dichalcogenides have an intriguing crystal structure consisting of long tetrahedral chains held together by van der Waals forces but the electronic and optical properties have been less explored. In the present work, bulk SiSe 2 , SiS 2 , and Si(Se x S 1-x) 2 were synthesized by the congruent melt growth method and characterized by Raman spectroscopy, X-ray Diffraction and UV/visible/IR transmission measurements supported by first-principles calculations. First-principles calculations reveal a nearly linear decrease of band gap energy in Si(Se x S 1-x) 2 with increasing Se content, i.e., from SiS 2 to SiSe 2 which corresponds with a blue-shift in the transmission spectra from bulk SiSe 2 to Si(Se 0.6 S 0.4) 2 , and to SiS 2. Air stability tests demonstrate the formation of toxic H 2 Se/H 2 S gas from sample oxidation at room temperature upon exposure to ambient air, and great care should be paid when handling these materials.

Lateral Versus Vertical Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Thermodynamic Insight into MoS2

“…Note that MoS 2 is moisture stable due to the positive reaction Gibbs energy for "MoS 2 (s) + 2 H 2 O (g) → MoO 2 (s) + 2 H 2 S (g)", unlike the moisture unstable compounds ZrS 2 and Si(S,Se) 2 . 34,41 According to thermodynamics, the final reaction products can be predicted via equilibrium calculations by minimizing the Gibbs energy. Figure 6b shows that MoS 2 and gas are the products under the S-rich condition at high temperatures (Case 1), while the final In summary, an integrated DFT calculation and CALPHAD modeling approach has been employed in the present work to understand the lateral versus vertical growth of the prototypical 2D material MoS 2 and provide pressure−temperature− composition (P-T-x) growth windows for the layer-thicknessdependent MoS 2 layers and the 2D lateral size-dependent MoS 2 flakes.…”

“…Figure a shows that the lowest reaction Gibbs energy is for the reaction “Mo (s) + 2 S (g) → MoS 2 (s)” and the most possible reaction from MoO 3 /MoO 2 to MoS 2 is “MoO 2 (s) + 2 S (g) → MoS 2 (s) + O 2 (g)”, where the letters “s” and “g” indicate solid and gas phase, respectively. Note that MoS 2 is moisture stable due to the positive reaction Gibbs energy for “MoS 2 (s) + 2 H 2 O (g) → MoO 2 (s) + 2 H 2 S (g)”, unlike the moisture unstable compounds ZrS 2 and Si­(S,Se) 2 . , According to thermodynamics, the final reaction products can be predicted via equilibrium calculations by minimizing the Gibbs energy. Figure b shows that MoS 2 and gas are the products under the S-rich condition at high temperatures (Case 1), while the final products are MoO 2 , MoS 2 , and gas under the S-lean condition (Case 2).…”

First-principles calculations of lattice dynamics and thermal properties of polar solids

“…91 layered antimony telluride, 92 Phonon transport in SrTiO 3 , 93 self-consistent phonon calculations for cubic SrTiO 3 (ref. 94) and Si(Se x S 1 − x ) 2 95.…”

Structural and Topological Evolution in SixSe1–x Glasses: Results from 1D and 2D 29Si and 77Se NMR Spectroscopy

“…Accordingly, the 29 Si isotropic line shapes are simulated with four components centered at −89, −59, and −28, and −17 ppm (Figure 6 and Table 3). The first three components can be readily assigned, on the basis of previous 29 Si MAS NMR studies on various crystalline SiSe 2 polymorphs, 20 to tetrahedral Si sites that belong to the E 2 , E 1 , and E 0 environments (Figure 1), respectively. The Δ for these environments progressively increase with increasing degree of edge sharing (Table 2).…”