Monitoring the Material Quality of Two-Dimensional Transition Metal Dichalcogenides

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs), with atomic thickness, strong spin–orbit coupling, enhanced light-matter interactions. and facile quantum control ability, have demonstrated great potential in the applications of nanoelectronics and optoelectronics. The realization of these high-performance applications strongly relies on the production of large-scale TMD films with high quality. Therefore, facile and accurate quality monitoring of TMDs is essential for their future applications. In this Review, we summarized the main defect types in TMD crystals obtained by different synthesis methods, and we discussed recent cutting-edge characterization techniques, including scanning transmission electron microscopy, etching or adsorption, optical spectroscopy, and field-effect transistors. Finally, we provide a short perspective on the future development of quality monitoring techniques for broad 2D materials.

Efficient and Facile Synthetic Route of MoO3:MoS2 Hybrid Thin Layer via Oxidative Reaction of MoS2 Nanoflakes

“…To discuss the reaction process, S 2p and O1s spectra of the hybrid thin film are illustrated in Figure 7; it can be seen in the S2p spectrum that there is a spinorbit doublet at the binding energy of 161 eV and 163 eV corresponding to the oxidation state S 2− which also confirms the existence of MoS 2 moieties in the hybrid thin film [26]. Moreover, we have detected an additional weak peak at binding energy around 169 eV for the MoS 2 layer before oxidation [26,38]; the presence of this peak at higher binding energy is mostly attributed to the presence of sulfate (SO 4 2− ) due to air contamination and the exfoliation process of MoS 2 as reported in the previous works [35,39]. This peak becomes dominant at almost the same binding energy for the hybrid layer with the appearance of the Mo 5+ oxidation state which is attributed to the existence of MoOxSy.…”

“…to the Mo 5+ oxidation state that can be attributed to the MoOxSy (Table 1); the presence of a low quantity of this intermediate product in MoS2 thin film is coming from MoS2 oxidation during the exfoliation process [35]. After MoS2 oxidation using H2O2, we can observe a doublet peak with high intensity at 232.6 eV and 235.6 eV corresponding to MoO3 [27] and MoS2 at binding energies of 229 eV and 232 eV.…”

“…Firstly, Mo 3d spectra of MoO 3 :MoS 2 and MoS 2 thin films deposited on the ITO/PET substrate are presented in Figure 6. From the Mo3d spectrum of MoS 2 thin film, we can observe two doublets, the first at almost 229 eV and 232 eV corresponding to MoS 2 and the second doublet at almost 232 eV and 235 eV which correspond to the Mo 5+ oxidation state that can be attributed to the MoOxSy (Table 1); the presence of a low quantity of this intermediate product in MoS 2 thin film is coming from MoS 2 oxidation during the exfoliation process [35]. After MoS 2 oxidation using H 2 O 2 , we can observe a doublet peak with high intensity at 232.6 eV and 235.6 eV corresponding to MoO 3 [27] and MoS 2 at binding energies of 229 eV and 232 eV.…”