Amorphous-to-Crystal Transition in Quasi-Two-Dimensional MoS₂: Implications for 2D Electronic Devices

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have demonstrated a very strong application potential. In order to realize it, the synthesis of stoichiometric 2D TMDCs on a large scale is crucial. Here, we consider a typical TMDC representative, MoS 2 , and present an approach for the fabrication of well-ordered crystalline films via the crystallization of a thin amorphous layer by annealing at 800 °C, which was investigated in terms of long-range and short-range orders. Strong preferential crystal growth of layered MoS 2 along the ⟨002⟩ crystallographic plane from the as-deposited 3D amorphous phase is discussed together with the mechanism of the crystallization process disclosed by molecular dynamic simulations using the Vienna Ab initio Simulation Package. We believe that the obtained results may be generalized for other 2D materials. The proposed approach demonstrates a simple and efficient way to fabricate thin 2D TMDCs for applications in nanoand optoelectronic devices.

Atomic Layer Deposition of Large-Area Polycrystalline Transition Metal Dichalcogenides from 100 °C through Control of Plasma Chemistry

“… 57 The doublet between the Mo 4+ and Mo 6+ doublets is assigned to Mo 5+ (MoO y S x ), an intermediate oxidation product. 58 , 59 For c-MoS 2 films, an additional low-intensity doublet at a lower BE compared to Mo 4+ was required to obtain a satisfactory fit. This doublet is denoted as Mo (4−δ)+ as it was attributed to more metallic Mo atoms present at the edges of MoS 2 crystals, 60 in the metastable 1T′ phase of MoS 2 , 61 or MoS 2– x subsulfide.…”

Strain-regulated Gibbs free energy enables reversible redox chemistry of chalcogenides for sodium ion batteries

“…In contrast, after the full charging, the aforesaid peaks almost recover to the original state of TS-MoSe 2 , while the Mo foil-related features disappear, indicating that the discharging and charging processes of TS-MoSe 2 during the initial cycle are nearly fully reversible. It should be noted that the Mo K-edge XANES spectra of formed metallic Mo and the regenerated MoSe 2 are slightly different from those of corresponding Mo foil and pristine TS-MoSe 2 , which may be caused by the ligand effect of imidazole and amorphous nature, respectively 41 , 42 . A similar change trend is also observed in the Se K-edge XANES (Supplementary Figs.…”

Improved Ordering of Quasi-Two-Dimensional MoS2 via an Amorphous-to-Crystal Transition Initiated from Amorphous Sulfur-Rich MoS2+x

“…On the other hand, the Mo K edge XANES spectra for both versions of crystallized MoS 2 are very similar, corroborating that the final products of both amorphous phases have the same structure after crystallization. 28,33 However, a detailed comparison indicated that, for crystallized MoS 2 originating from amorphous MoS 2 , the intensity of the so-called white-line is lower and the overall shape of the XANES spectrum is more rounded compared to the counterpart XANES spectrum of MoS 2 originating from MoS 4 , suggesting that the former structure is less ordered. The results of the real-space fitting of the EXAFS data of the amorphous and crystalline phases are summarized in Table 1.…”

“…These values are in line with previously reported results. 28,33,36,37 The coordination numbers of the first (Mo−S) and second (Mo− Mo) coordination shells are 5.90 and 4.19 for crystallized MoS 2 originating from MoS 2 and 6.29 and 7.67 for that originating from MoS 4 , leading to the conclusion that the crystalline MoS 2 phase originating from MoS 4 is clearly better ordered. We would like to emphasize that the conclusion from the EXAFS experiment is in excellent agreement with the XRD analysis.…”