Structure Re‐determination and Superconductivity Observation of Bulk 1T MoS₂

Abstract

Figure 1a). [2] The metastable 1T MoS2 was reported to have A-b-C layers with edge-sharing [MoS6] octahedron (see Figure 1b), which was derived from electron diffraction [3] and powder X-ray pattern. [4] But the crystal structure of 1T MoS2 has never been collected in the Inorganic Crystal Structure Database (ICSD) due to the lack of a strict structural refinement.Although the single-layer 1T MoS2 has been prepared by using various synthetic methods, [5] the obtained nanosheets always coexist with 2H, 1T, and 1T' phases. The maximal content of 1T/1T' domains have been reported to be up to 80% which was evaluated by XPS measurements.[5b] The 1T/1T' MoS2 phases were observed to start the transformation to thermodynamically more stable 2H phase at around 100 C and be completely converted into 2H phase at 300 C. [6] It was recently reported that 1T/1T' MoS2 domains can be stabilized by electron doping. [7] 2H MoS2 intrinsically behaves as a semiconductor with a band gap of 1.2-1.9 eV, [8] which is consistent with the closeshell electronic configuration of Mo 4+ 4d 2 (dz 2 , dx 2 -y 2 ) in a trigonal prismatic coordination environment (Figure 1a). [9] Previously reported superconductivity in the MoS2 system is based on electron injection to the Fermi surface of 2H MoS2 [9] shown in Figure 1b, whose two electrons are filled in the t states and may also become itinerant electrons. Anomalous superconductivity has recently been reported in the structure-related 1T' MoTe2 at a very low Tc of about 0.1 K.[12] The density functional calculations predicted the metallicity of 1T MoS2. [13] However, the sample of MoS2 nanosheets coexisting with 1T/1T' and 2H phases was found to have a semiconducting behavior. [14] Moreover, the superconductivity of 1T MoS2 has never been discovered yet.So far, it is very important and urgent to synthesize single crystals of 1T-MoS2 for re-determining single crystal structure and investigating intrinsic physical properties. Here, we reported a modified strategy derived from the literature The preparation of 1T-MoS2 started from the intercalated compound LiMoS2, whose synthesis process was described by our previous results. [15] The oxidation processes of LiMoS2 crystals were divided into two steps, in which the corresponding reactions happen as follow:In the first step, lithium atoms undergo the hydration process, which expands the interlayer distance of MoS2. Figure S1a shows the PXRD pattern of as-obtained Li1-x(H2O)yMoS2, which corresponds to 12.149 Å of the d value along the c direction. Expanded layer spacing reduces the interactions between sulfur atoms and lithium atoms, which promotes the removal of lithium ion in the second redox process. Moreover, the deintercalation of Li ions causes fewer damages on the crystal structure of 1T MoS2 compared with that caused by the deintercalation of K ions.[3], [4] As illustrated in Figure 1b, the 1T-MoS2 crystallizes in the trigonal space group P-3m1. The unit cell consists of one independent Mo site and one independent S site. Each layer...

Structural and electronic phase transitions driven by electric field in metastable MoS2 thin flakes

“…Comparing to the pristine 1T -MoS 2 , the relative changes in the peak intensity could be due to the defects caused by the migration of Li ions. In particular, the resistance measurements also indicate that the metallicity and superconductivity are highly consistent with previous reports on 1T -MoS 2 superconductor [30,31,39]. We have also performed high spatial-resolution Raman measurements to study the structural homogeneity of the sample at V g = 0 V, 3 V and -3 V, and found that the structural transitions are uniform in the thin flake upon the intercalation and de-intercalation of Li ions (see Fig.…”

Synergistic Doping and Intercalation: Realizing Deep Phase Modulation on MoS2 Arrays for High‐Efficiency Hydrogen Evolution Reaction

“…Impressively,t he (002) peak of (N,PO 4 3À )-MoS 2 /VGshows the strongest left shift, implying that the degree of phase transformation from 2H-MoS 2 to 1T-MoS 2 is deeper in (N,PO 4 3À )-MoS 2 /VG. [21] Raman spectra further verify the conclusion above.The characteristic Raman peaks at 380 and 405 cm À1 can be observed in the spectra of all samples (Supporting Information, Figure S7b) and these two peaks belong to E 1 2g (in-plane) and A 1g (out-of-plane) vibrations of MoS 2 , [1,7,8] While there are only E 1 2g ,A 1g ,a nd E 1g peaks for MoS 2 /VG, suggesting its typical 2H-phase. )-MoS 2 /VGn ot only presents the weakest characteristic peaks of E 1 2g and A 1g ,but also exhibits other strong characteristic peaks of 1T-MoS 2 ,w hich are attributed to J 1 ,J 2 ,a nd J 3 vibration modes of S-Mo-S bonds.…”

“…Tw o-dimensional (2D) transition-metal dichalcogenides (TMDs,s uch as MoS 2 )h ave been the research hotspot over the past decade owing to their unique electronic structures, controllable band gap,a nd adjustable phase components, which are the key to achieve high performance for optical and electrochemical applications. [1] As atypical representative of 2D layer-structured materials,M oS 2 possesses different phases including thermodynamically stable trigonal prismatic 2H phase,o ctahedral coordinated 1T phase,a nd distorted octahedral coordinated 1T'-phase. [2,3] It has been demonstrated that the electrochemical reactivity and reaction kinetics of MoS 2 are closely bound up with its phase component.…”

Structure Re‐determination and Superconductivity Observation of Bulk 1T MoS2

“…It is very important and urgent to synthesize single crystals of 1T-MoS 2 for re-determining the single-crystal structure and to investigate intrinsic physical properties.Herein, we report am odified strategy derived from the literature [4] to prepare metastable 1T-MoS 2 single crystals.T he crystal structure of 1T-MoS 2 was determined by single-crystal X-ray diffraction for the first time. [15] The1 T-MoS 2 crystal structures are confirmed through scanning transmission electron microscopy (STEM) and aRaman spectrum. Thesuperconductivity of 1T MoS 2 at 4K was observed for the first time.T he zerotemperature upper critical magnetic field of 1T-MoS 2 is estimated to be 5.02 Tbased on the temperature dependence of the upper critical magnetic field.…”